/* * Budget Fair Queueing (BFQ) I/O scheduler. * * Based on ideas and code from CFQ: * Copyright (C) 2003 Jens Axboe * * Copyright (C) 2008 Fabio Checconi * Paolo Valente * * Copyright (C) 2010 Paolo Valente * Arianna Avanzini * * Copyright (C) 2017 Paolo Valente * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation; either version 2 of the * License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * BFQ is a proportional-share I/O scheduler, with some extra * low-latency capabilities. BFQ also supports full hierarchical * scheduling through cgroups. Next paragraphs provide an introduction * on BFQ inner workings. Details on BFQ benefits, usage and * limitations can be found in Documentation/block/bfq-iosched.txt. * * BFQ is a proportional-share storage-I/O scheduling algorithm based * on the slice-by-slice service scheme of CFQ. But BFQ assigns * budgets, measured in number of sectors, to processes instead of * time slices. The device is not granted to the in-service process * for a given time slice, but until it has exhausted its assigned * budget. This change from the time to the service domain enables BFQ * to distribute the device throughput among processes as desired, * without any distortion due to throughput fluctuations, or to device * internal queueing. BFQ uses an ad hoc internal scheduler, called * B-WF2Q+, to schedule processes according to their budgets. More * precisely, BFQ schedules queues associated with processes. Each * process/queue is assigned a user-configurable weight, and B-WF2Q+ * guarantees that each queue receives a fraction of the throughput * proportional to its weight. Thanks to the accurate policy of * B-WF2Q+, BFQ can afford to assign high budgets to I/O-bound * processes issuing sequential requests (to boost the throughput), * and yet guarantee a low latency to interactive and soft real-time * applications. * * In particular, to provide these low-latency guarantees, BFQ * explicitly privileges the I/O of two classes of time-sensitive * applications: interactive and soft real-time. This feature enables * BFQ to provide applications in these classes with a very low * latency. Finally, BFQ also features additional heuristics for * preserving both a low latency and a high throughput on NCQ-capable, * rotational or flash-based devices, and to get the job done quickly * for applications consisting in many I/O-bound processes. * * BFQ is described in [1], where also a reference to the initial, more * theoretical paper on BFQ can be found. The interested reader can find * in the latter paper full details on the main algorithm, as well as * formulas of the guarantees and formal proofs of all the properties. * With respect to the version of BFQ presented in these papers, this * implementation adds a few more heuristics, such as the one that * guarantees a low latency to soft real-time applications, and a * hierarchical extension based on H-WF2Q+. * * B-WF2Q+ is based on WF2Q+, which is described in [2], together with * H-WF2Q+, while the augmented tree used here to implement B-WF2Q+ * with O(log N) complexity derives from the one introduced with EEVDF * in [3]. * * [1] P. Valente, A. Avanzini, "Evolution of the BFQ Storage I/O * Scheduler", Proceedings of the First Workshop on Mobile System * Technologies (MST-2015), May 2015. * http://algogroup.unimore.it/people/paolo/disk_sched/mst-2015.pdf * * [2] Jon C.R. Bennett and H. Zhang, "Hierarchical Packet Fair Queueing * Algorithms", IEEE/ACM Transactions on Networking, 5(5):675-689, * Oct 1997. * * http://www.cs.cmu.edu/~hzhang/papers/TON-97-Oct.ps.gz * * [3] I. Stoica and H. Abdel-Wahab, "Earliest Eligible Virtual Deadline * First: A Flexible and Accurate Mechanism for Proportional Share * Resource Allocation", technical report. * * http://www.cs.berkeley.edu/~istoica/papers/eevdf-tr-95.pdf */ #include #include #include #include #include #include #include #include #include #include #include "blk.h" #include "blk-mq.h" #include "blk-mq-tag.h" #include "blk-mq-sched.h" #include #include #include #define BFQ_IOPRIO_CLASSES 3 #define BFQ_CL_IDLE_TIMEOUT (HZ/5) #define BFQ_MIN_WEIGHT 1 #define BFQ_MAX_WEIGHT 1000 #define BFQ_WEIGHT_CONVERSION_COEFF 10 #define BFQ_DEFAULT_QUEUE_IOPRIO 4 #define BFQ_WEIGHT_LEGACY_DFL 100 #define BFQ_DEFAULT_GRP_IOPRIO 0 #define BFQ_DEFAULT_GRP_CLASS IOPRIO_CLASS_BE /* * Soft real-time applications are extremely more latency sensitive * than interactive ones. Over-raise the weight of the former to * privilege them against the latter. */ #define BFQ_SOFTRT_WEIGHT_FACTOR 100 struct bfq_entity; /** * struct bfq_service_tree - per ioprio_class service tree. * * Each service tree represents a B-WF2Q+ scheduler on its own. Each * ioprio_class has its own independent scheduler, and so its own * bfq_service_tree. All the fields are protected by the queue lock * of the containing bfqd. */ struct bfq_service_tree { /* tree for active entities (i.e., those backlogged) */ struct rb_root active; /* tree for idle entities (i.e., not backlogged, with V <= F_i)*/ struct rb_root idle; /* idle entity with minimum F_i */ struct bfq_entity *first_idle; /* idle entity with maximum F_i */ struct bfq_entity *last_idle; /* scheduler virtual time */ u64 vtime; /* scheduler weight sum; active and idle entities contribute to it */ unsigned long wsum; }; /** * struct bfq_sched_data - multi-class scheduler. * * bfq_sched_data is the basic scheduler queue. It supports three * ioprio_classes, and can be used either as a toplevel queue or as an * intermediate queue on a hierarchical setup. @next_in_service * points to the active entity of the sched_data service trees that * will be scheduled next. It is used to reduce the number of steps * needed for each hierarchical-schedule update. * * The supported ioprio_classes are the same as in CFQ, in descending * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE. * Requests from higher priority queues are served before all the * requests from lower priority queues; among requests of the same * queue requests are served according to B-WF2Q+. * All the fields are protected by the queue lock of the containing bfqd. */ struct bfq_sched_data { /* entity in service */ struct bfq_entity *in_service_entity; /* head-of-line entity (see comments above) */ struct bfq_entity *next_in_service; /* array of service trees, one per ioprio_class */ struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES]; /* last time CLASS_IDLE was served */ unsigned long bfq_class_idle_last_service; }; /** * struct bfq_entity - schedulable entity. * * A bfq_entity is used to represent either a bfq_queue (leaf node in the * cgroup hierarchy) or a bfq_group into the upper level scheduler. Each * entity belongs to the sched_data of the parent group in the cgroup * hierarchy. Non-leaf entities have also their own sched_data, stored * in @my_sched_data. * * Each entity stores independently its priority values; this would * allow different weights on different devices, but this * functionality is not exported to userspace by now. Priorities and * weights are updated lazily, first storing the new values into the * new_* fields, then setting the @prio_changed flag. As soon as * there is a transition in the entity state that allows the priority * update to take place the effective and the requested priority * values are synchronized. * * Unless cgroups are used, the weight value is calculated from the * ioprio to export the same interface as CFQ. When dealing with * ``well-behaved'' queues (i.e., queues that do not spend too much * time to consume their budget and have true sequential behavior, and * when there are no external factors breaking anticipation) the * relative weights at each level of the cgroups hierarchy should be * guaranteed. All the fields are protected by the queue lock of the * containing bfqd. */ struct bfq_entity { /* service_tree member */ struct rb_node rb_node; /* * Flag, true if the entity is on a tree (either the active or * the idle one of its service_tree) or is in service. */ bool on_st; /* B-WF2Q+ start and finish timestamps [sectors/weight] */ u64 start, finish; /* tree the entity is enqueued into; %NULL if not on a tree */ struct rb_root *tree; /* * minimum start time of the (active) subtree rooted at this * entity; used for O(log N) lookups into active trees */ u64 min_start; /* amount of service received during the last service slot */ int service; /* budget, used also to calculate F_i: F_i = S_i + @budget / @weight */ int budget; /* weight of the queue */ int weight; /* next weight if a change is in progress */ int new_weight; /* original weight, used to implement weight boosting */ int orig_weight; /* parent entity, for hierarchical scheduling */ struct bfq_entity *parent; /* * For non-leaf nodes in the hierarchy, the associated * scheduler queue, %NULL on leaf nodes. */ struct bfq_sched_data *my_sched_data; /* the scheduler queue this entity belongs to */ struct bfq_sched_data *sched_data; /* flag, set to request a weight, ioprio or ioprio_class change */ int prio_changed; }; struct bfq_group; /** * struct bfq_ttime - per process thinktime stats. */ struct bfq_ttime { /* completion time of the last request */ u64 last_end_request; /* total process thinktime */ u64 ttime_total; /* number of thinktime samples */ unsigned long ttime_samples; /* average process thinktime */ u64 ttime_mean; }; /** * struct bfq_queue - leaf schedulable entity. * * A bfq_queue is a leaf request queue; it can be associated with an * io_context or more, if it is async or shared between cooperating * processes. @cgroup holds a reference to the cgroup, to be sure that it * does not disappear while a bfqq still references it (mostly to avoid * races between request issuing and task migration followed by cgroup * destruction). * All the fields are protected by the queue lock of the containing bfqd. */ struct bfq_queue { /* reference counter */ int ref; /* parent bfq_data */ struct bfq_data *bfqd; /* current ioprio and ioprio class */ unsigned short ioprio, ioprio_class; /* next ioprio and ioprio class if a change is in progress */ unsigned short new_ioprio, new_ioprio_class; /* * Shared bfq_queue if queue is cooperating with one or more * other queues. */ struct bfq_queue *new_bfqq; /* request-position tree member (see bfq_group's @rq_pos_tree) */ struct rb_node pos_node; /* request-position tree root (see bfq_group's @rq_pos_tree) */ struct rb_root *pos_root; /* sorted list of pending requests */ struct rb_root sort_list; /* if fifo isn't expired, next request to serve */ struct request *next_rq; /* number of sync and async requests queued */ int queued[2]; /* number of requests currently allocated */ int allocated; /* number of pending metadata requests */ int meta_pending; /* fifo list of requests in sort_list */ struct list_head fifo; /* entity representing this queue in the scheduler */ struct bfq_entity entity; /* maximum budget allowed from the feedback mechanism */ int max_budget; /* budget expiration (in jiffies) */ unsigned long budget_timeout; /* number of requests on the dispatch list or inside driver */ int dispatched; /* status flags */ unsigned long flags; /* node for active/idle bfqq list inside parent bfqd */ struct list_head bfqq_list; /* associated @bfq_ttime struct */ struct bfq_ttime ttime; /* bit vector: a 1 for each seeky requests in history */ u32 seek_history; /* position of the last request enqueued */ sector_t last_request_pos; /* Number of consecutive pairs of request completion and * arrival, such that the queue becomes idle after the * completion, but the next request arrives within an idle * time slice; used only if the queue's IO_bound flag has been * cleared. */ unsigned int requests_within_timer; /* pid of the process owning the queue, used for logging purposes */ pid_t pid; /* * Pointer to the bfq_io_cq owning the bfq_queue, set to %NULL * if the queue is shared. */ struct bfq_io_cq *bic; /* current maximum weight-raising time for this queue */ unsigned long wr_cur_max_time; /* * Minimum time instant such that, only if a new request is * enqueued after this time instant in an idle @bfq_queue with * no outstanding requests, then the task associated with the * queue it is deemed as soft real-time (see the comments on * the function bfq_bfqq_softrt_next_start()) */ unsigned long soft_rt_next_start; /* * Start time of the current weight-raising period if * the @bfq-queue is being weight-raised, otherwise * finish time of the last weight-raising period. */ unsigned long last_wr_start_finish; /* factor by which the weight of this queue is multiplied */ unsigned int wr_coeff; /* * Time of the last transition of the @bfq_queue from idle to * backlogged. */ unsigned long last_idle_bklogged; /* * Cumulative service received from the @bfq_queue since the * last transition from idle to backlogged. */ unsigned long service_from_backlogged; /* * Value of wr start time when switching to soft rt */ unsigned long wr_start_at_switch_to_srt; unsigned long split_time; /* time of last split */ }; /** * struct bfq_io_cq - per (request_queue, io_context) structure. */ struct bfq_io_cq { /* associated io_cq structure */ struct io_cq icq; /* must be the first member */ /* array of two process queues, the sync and the async */ struct bfq_queue *bfqq[2]; /* per (request_queue, blkcg) ioprio */ int ioprio; #ifdef CONFIG_BFQ_GROUP_IOSCHED uint64_t blkcg_serial_nr; /* the current blkcg serial */ #endif /* * Snapshot of the idle window before merging; taken to * remember this value while the queue is merged, so as to be * able to restore it in case of split. */ bool saved_idle_window; /* * Same purpose as the previous two fields for the I/O bound * classification of a queue. */ bool saved_IO_bound; /* * Similar to previous fields: save wr information. */ unsigned long saved_wr_coeff; unsigned long saved_last_wr_start_finish; unsigned long saved_wr_start_at_switch_to_srt; unsigned int saved_wr_cur_max_time; struct bfq_ttime saved_ttime; }; enum bfq_device_speed { BFQ_BFQD_FAST, BFQ_BFQD_SLOW, }; /** * struct bfq_data - per-device data structure. * * All the fields are protected by @lock. */ struct bfq_data { /* device request queue */ struct request_queue *queue; /* dispatch queue */ struct list_head dispatch; /* root bfq_group for the device */ struct bfq_group *root_group; /* * Number of bfq_queues containing requests (including the * queue in service, even if it is idling). */ int busy_queues; /* number of weight-raised busy @bfq_queues */ int wr_busy_queues; /* number of queued requests */ int queued; /* number of requests dispatched and waiting for completion */ int rq_in_driver; /* * Maximum number of requests in driver in the last * @hw_tag_samples completed requests. */ int max_rq_in_driver; /* number of samples used to calculate hw_tag */ int hw_tag_samples; /* flag set to one if the driver is showing a queueing behavior */ int hw_tag; /* number of budgets assigned */ int budgets_assigned; /* * Timer set when idling (waiting) for the next request from * the queue in service. */ struct hrtimer idle_slice_timer; /* bfq_queue in service */ struct bfq_queue *in_service_queue; /* bfq_io_cq (bic) associated with the @in_service_queue */ struct bfq_io_cq *in_service_bic; /* on-disk position of the last served request */ sector_t last_position; /* time of last request completion (ns) */ u64 last_completion; /* time of first rq dispatch in current observation interval (ns) */ u64 first_dispatch; /* time of last rq dispatch in current observation interval (ns) */ u64 last_dispatch; /* beginning of the last budget */ ktime_t last_budget_start; /* beginning of the last idle slice */ ktime_t last_idling_start; /* number of samples in current observation interval */ int peak_rate_samples; /* num of samples of seq dispatches in current observation interval */ u32 sequential_samples; /* total num of sectors transferred in current observation interval */ u64 tot_sectors_dispatched; /* max rq size seen during current observation interval (sectors) */ u32 last_rq_max_size; /* time elapsed from first dispatch in current observ. interval (us) */ u64 delta_from_first; /* * Current estimate of the device peak rate, measured in * [BFQ_RATE_SHIFT * sectors/usec]. The left-shift by * BFQ_RATE_SHIFT is performed to increase precision in * fixed-point calculations. */ u32 peak_rate; /* maximum budget allotted to a bfq_queue before rescheduling */ int bfq_max_budget; /* list of all the bfq_queues active on the device */ struct list_head active_list; /* list of all the bfq_queues idle on the device */ struct list_head idle_list; /* * Timeout for async/sync requests; when it fires, requests * are served in fifo order. */ u64 bfq_fifo_expire[2]; /* weight of backward seeks wrt forward ones */ unsigned int bfq_back_penalty; /* maximum allowed backward seek */ unsigned int bfq_back_max; /* maximum idling time */ u32 bfq_slice_idle; /* user-configured max budget value (0 for auto-tuning) */ int bfq_user_max_budget; /* * Timeout for bfq_queues to consume their budget; used to * prevent seeky queues from imposing long latencies to * sequential or quasi-sequential ones (this also implies that * seeky queues cannot receive guarantees in the service * domain; after a timeout they are charged for the time they * have been in service, to preserve fairness among them, but * without service-domain guarantees). */ unsigned int bfq_timeout; /* * Number of consecutive requests that must be issued within * the idle time slice to set again idling to a queue which * was marked as non-I/O-bound (see the definition of the * IO_bound flag for further details). */ unsigned int bfq_requests_within_timer; /* * Force device idling whenever needed to provide accurate * service guarantees, without caring about throughput * issues. CAVEAT: this may even increase latencies, in case * of useless idling for processes that did stop doing I/O. */ bool strict_guarantees; /* if set to true, low-latency heuristics are enabled */ bool low_latency; /* * Maximum factor by which the weight of a weight-raised queue * is multiplied. */ unsigned int bfq_wr_coeff; /* maximum duration of a weight-raising period (jiffies) */ unsigned int bfq_wr_max_time; /* Maximum weight-raising duration for soft real-time processes */ unsigned int bfq_wr_rt_max_time; /* * Minimum idle period after which weight-raising may be * reactivated for a queue (in jiffies). */ unsigned int bfq_wr_min_idle_time; /* * Minimum period between request arrivals after which * weight-raising may be reactivated for an already busy async * queue (in jiffies). */ unsigned long bfq_wr_min_inter_arr_async; /* Max service-rate for a soft real-time queue, in sectors/sec */ unsigned int bfq_wr_max_softrt_rate; /* * Cached value of the product R*T, used for computing the * maximum duration of weight raising automatically. */ u64 RT_prod; /* device-speed class for the low-latency heuristic */ enum bfq_device_speed device_speed; /* fallback dummy bfqq for extreme OOM conditions */ struct bfq_queue oom_bfqq; spinlock_t lock; /* * bic associated with the task issuing current bio for * merging. This and the next field are used as a support to * be able to perform the bic lookup, needed by bio-merge * functions, before the scheduler lock is taken, and thus * avoid taking the request-queue lock while the scheduler * lock is being held. */ struct bfq_io_cq *bio_bic; /* bfqq associated with the task issuing current bio for merging */ struct bfq_queue *bio_bfqq; /* * io context to put right after bfqd->lock is released. This * filed is used to perform put_io_context, when needed, to * after the scheduler lock has been released, and thus * prevent an ioc->lock from being possibly taken while the * scheduler lock is being held. */ struct io_context *ioc_to_put; }; enum bfqq_state_flags { BFQQF_busy = 0, /* has requests or is in service */ BFQQF_wait_request, /* waiting for a request */ BFQQF_non_blocking_wait_rq, /* * waiting for a request * without idling the device */ BFQQF_fifo_expire, /* FIFO checked in this slice */ BFQQF_idle_window, /* slice idling enabled */ BFQQF_sync, /* synchronous queue */ BFQQF_IO_bound, /* * bfqq has timed-out at least once * having consumed at most 2/10 of * its budget */ BFQQF_softrt_update, /* * may need softrt-next-start * update */ BFQQF_coop, /* bfqq is shared */ BFQQF_split_coop /* shared bfqq will be split */ }; #define BFQ_BFQQ_FNS(name) \ static void bfq_mark_bfqq_##name(struct bfq_queue *bfqq) \ { \ __set_bit(BFQQF_##name, &(bfqq)->flags); \ } \ static void bfq_clear_bfqq_##name(struct bfq_queue *bfqq) \ { \ __clear_bit(BFQQF_##name, &(bfqq)->flags); \ } \ static int bfq_bfqq_##name(const struct bfq_queue *bfqq) \ { \ return test_bit(BFQQF_##name, &(bfqq)->flags); \ } BFQ_BFQQ_FNS(busy); BFQ_BFQQ_FNS(wait_request); BFQ_BFQQ_FNS(non_blocking_wait_rq); BFQ_BFQQ_FNS(fifo_expire); BFQ_BFQQ_FNS(idle_window); BFQ_BFQQ_FNS(sync); BFQ_BFQQ_FNS(IO_bound); BFQ_BFQQ_FNS(coop); BFQ_BFQQ_FNS(split_coop); BFQ_BFQQ_FNS(softrt_update); #undef BFQ_BFQQ_FNS /* Logging facilities. */ #ifdef CONFIG_BFQ_GROUP_IOSCHED static struct bfq_group *bfqq_group(struct bfq_queue *bfqq); static struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg); #define bfq_log_bfqq(bfqd, bfqq, fmt, args...) do { \ char __pbuf[128]; \ \ blkg_path(bfqg_to_blkg(bfqq_group(bfqq)), __pbuf, sizeof(__pbuf)); \ blk_add_trace_msg((bfqd)->queue, "bfq%d%c %s " fmt, (bfqq)->pid, \ bfq_bfqq_sync((bfqq)) ? 'S' : 'A', \ __pbuf, ##args); \ } while (0) #define bfq_log_bfqg(bfqd, bfqg, fmt, args...) do { \ char __pbuf[128]; \ \ blkg_path(bfqg_to_blkg(bfqg), __pbuf, sizeof(__pbuf)); \ blk_add_trace_msg((bfqd)->queue, "%s " fmt, __pbuf, ##args); \ } while (0) #else /* CONFIG_BFQ_GROUP_IOSCHED */ #define bfq_log_bfqq(bfqd, bfqq, fmt, args...) \ blk_add_trace_msg((bfqd)->queue, "bfq%d%c " fmt, (bfqq)->pid, \ bfq_bfqq_sync((bfqq)) ? 'S' : 'A', \ ##args) #define bfq_log_bfqg(bfqd, bfqg, fmt, args...) do {} while (0) #endif /* CONFIG_BFQ_GROUP_IOSCHED */ #define bfq_log(bfqd, fmt, args...) \ blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args) /* Expiration reasons. */ enum bfqq_expiration { BFQQE_TOO_IDLE = 0, /* * queue has been idling for * too long */ BFQQE_BUDGET_TIMEOUT, /* budget took too long to be used */ BFQQE_BUDGET_EXHAUSTED, /* budget consumed */ BFQQE_NO_MORE_REQUESTS, /* the queue has no more requests */ BFQQE_PREEMPTED /* preemption in progress */ }; struct bfqg_stats { #ifdef CONFIG_BFQ_GROUP_IOSCHED /* number of ios merged */ struct blkg_rwstat merged; /* total time spent on device in ns, may not be accurate w/ queueing */ struct blkg_rwstat service_time; /* total time spent waiting in scheduler queue in ns */ struct blkg_rwstat wait_time; /* number of IOs queued up */ struct blkg_rwstat queued; /* total disk time and nr sectors dispatched by this group */ struct blkg_stat time; /* sum of number of ios queued across all samples */ struct blkg_stat avg_queue_size_sum; /* count of samples taken for average */ struct blkg_stat avg_queue_size_samples; /* how many times this group has been removed from service tree */ struct blkg_stat dequeue; /* total time spent waiting for it to be assigned a timeslice. */ struct blkg_stat group_wait_time; /* time spent idling for this blkcg_gq */ struct blkg_stat idle_time; /* total time with empty current active q with other requests queued */ struct blkg_stat empty_time; /* fields after this shouldn't be cleared on stat reset */ uint64_t start_group_wait_time; uint64_t start_idle_time; uint64_t start_empty_time; uint16_t flags; #endif /* CONFIG_BFQ_GROUP_IOSCHED */ }; #ifdef CONFIG_BFQ_GROUP_IOSCHED /* * struct bfq_group_data - per-blkcg storage for the blkio subsystem. * * @ps: @blkcg_policy_storage that this structure inherits * @weight: weight of the bfq_group */ struct bfq_group_data { /* must be the first member */ struct blkcg_policy_data pd; unsigned int weight; }; /** * struct bfq_group - per (device, cgroup) data structure. * @entity: schedulable entity to insert into the parent group sched_data. * @sched_data: own sched_data, to contain child entities (they may be * both bfq_queues and bfq_groups). * @bfqd: the bfq_data for the device this group acts upon. * @async_bfqq: array of async queues for all the tasks belonging to * the group, one queue per ioprio value per ioprio_class, * except for the idle class that has only one queue. * @async_idle_bfqq: async queue for the idle class (ioprio is ignored). * @my_entity: pointer to @entity, %NULL for the toplevel group; used * to avoid too many special cases during group creation/ * migration. * @stats: stats for this bfqg. * @rq_pos_tree: rbtree sorted by next_request position, used when * determining if two or more queues have interleaving * requests (see bfq_find_close_cooperator()). * * Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup * there is a set of bfq_groups, each one collecting the lower-level * entities belonging to the group that are acting on the same device. * * Locking works as follows: * o @bfqd is protected by the queue lock, RCU is used to access it * from the readers. * o All the other fields are protected by the @bfqd queue lock. */ struct bfq_group { /* must be the first member */ struct blkg_policy_data pd; struct bfq_entity entity; struct bfq_sched_data sched_data; void *bfqd; struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR]; struct bfq_queue *async_idle_bfqq; struct bfq_entity *my_entity; struct rb_root rq_pos_tree; struct bfqg_stats stats; }; #else struct bfq_group { struct bfq_sched_data sched_data; struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR]; struct bfq_queue *async_idle_bfqq; struct rb_root rq_pos_tree; }; #endif static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity); static unsigned int bfq_class_idx(struct bfq_entity *entity) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); return bfqq ? bfqq->ioprio_class - 1 : BFQ_DEFAULT_GRP_CLASS - 1; } static struct bfq_service_tree * bfq_entity_service_tree(struct bfq_entity *entity) { struct bfq_sched_data *sched_data = entity->sched_data; unsigned int idx = bfq_class_idx(entity); return sched_data->service_tree + idx; } static struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync) { return bic->bfqq[is_sync]; } static void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync) { bic->bfqq[is_sync] = bfqq; } static struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic) { return bic->icq.q->elevator->elevator_data; } #ifdef CONFIG_BFQ_GROUP_IOSCHED static struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq) { struct bfq_entity *group_entity = bfqq->entity.parent; if (!group_entity) group_entity = &bfqq->bfqd->root_group->entity; return container_of(group_entity, struct bfq_group, entity); } #else static struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq) { return bfqq->bfqd->root_group; } #endif static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio); static void bfq_put_queue(struct bfq_queue *bfqq); static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, struct bio *bio, bool is_sync, struct bfq_io_cq *bic); static void bfq_end_wr_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg); static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg); static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq); /* Expiration time of sync (0) and async (1) requests, in ns. */ static const u64 bfq_fifo_expire[2] = { NSEC_PER_SEC / 4, NSEC_PER_SEC / 8 }; /* Maximum backwards seek (magic number lifted from CFQ), in KiB. */ static const int bfq_back_max = 16 * 1024; /* Penalty of a backwards seek, in number of sectors. */ static const int bfq_back_penalty = 2; /* Idling period duration, in ns. */ static u64 bfq_slice_idle = NSEC_PER_SEC / 125; /* Minimum number of assigned budgets for which stats are safe to compute. */ static const int bfq_stats_min_budgets = 194; /* Default maximum budget values, in sectors and number of requests. */ static const int bfq_default_max_budget = 16 * 1024; /* * Async to sync throughput distribution is controlled as follows: * when an async request is served, the entity is charged the number * of sectors of the request, multiplied by the factor below */ static const int bfq_async_charge_factor = 10; /* Default timeout values, in jiffies, approximating CFQ defaults. */ static const int bfq_timeout = HZ / 8; static struct kmem_cache *bfq_pool; /* Below this threshold (in ns), we consider thinktime immediate. */ #define BFQ_MIN_TT (2 * NSEC_PER_MSEC) /* hw_tag detection: parallel requests threshold and min samples needed. */ #define BFQ_HW_QUEUE_THRESHOLD 4 #define BFQ_HW_QUEUE_SAMPLES 32 #define BFQQ_SEEK_THR (sector_t)(8 * 100) #define BFQQ_SECT_THR_NONROT (sector_t)(2 * 32) #define BFQQ_CLOSE_THR (sector_t)(8 * 1024) #define BFQQ_SEEKY(bfqq) (hweight32(bfqq->seek_history) > 32/8) /* Min number of samples required to perform peak-rate update */ #define BFQ_RATE_MIN_SAMPLES 32 /* Min observation time interval required to perform a peak-rate update (ns) */ #define BFQ_RATE_MIN_INTERVAL (300*NSEC_PER_MSEC) /* Target observation time interval for a peak-rate update (ns) */ #define BFQ_RATE_REF_INTERVAL NSEC_PER_SEC /* Shift used for peak rate fixed precision calculations. */ #define BFQ_RATE_SHIFT 16 /* * By default, BFQ computes the duration of the weight raising for * interactive applications automatically, using the following formula: * duration = (R / r) * T, where r is the peak rate of the device, and * R and T are two reference parameters. * In particular, R is the peak rate of the reference device (see below), * and T is a reference time: given the systems that are likely to be * installed on the reference device according to its speed class, T is * about the maximum time needed, under BFQ and while reading two files in * parallel, to load typical large applications on these systems. * In practice, the slower/faster the device at hand is, the more/less it * takes to load applications with respect to the reference device. * Accordingly, the longer/shorter BFQ grants weight raising to interactive * applications. * * BFQ uses four different reference pairs (R, T), depending on: * . whether the device is rotational or non-rotational; * . whether the device is slow, such as old or portable HDDs, as well as * SD cards, or fast, such as newer HDDs and SSDs. * * The device's speed class is dynamically (re)detected in * bfq_update_peak_rate() every time the estimated peak rate is updated. * * In the following definitions, R_slow[0]/R_fast[0] and * T_slow[0]/T_fast[0] are the reference values for a slow/fast * rotational device, whereas R_slow[1]/R_fast[1] and * T_slow[1]/T_fast[1] are the reference values for a slow/fast * non-rotational device. Finally, device_speed_thresh are the * thresholds used to switch between speed classes. The reference * rates are not the actual peak rates of the devices used as a * reference, but slightly lower values. The reason for using these * slightly lower values is that the peak-rate estimator tends to * yield slightly lower values than the actual peak rate (it can yield * the actual peak rate only if there is only one process doing I/O, * and the process does sequential I/O). * * Both the reference peak rates and the thresholds are measured in * sectors/usec, left-shifted by BFQ_RATE_SHIFT. */ static int R_slow[2] = {1000, 10700}; static int R_fast[2] = {14000, 33000}; /* * To improve readability, a conversion function is used to initialize the * following arrays, which entails that they can be initialized only in a * function. */ static int T_slow[2]; static int T_fast[2]; static int device_speed_thresh[2]; #define BFQ_SERVICE_TREE_INIT ((struct bfq_service_tree) \ { RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 }) #define RQ_BIC(rq) ((struct bfq_io_cq *) (rq)->elv.priv[0]) #define RQ_BFQQ(rq) ((rq)->elv.priv[1]) /** * icq_to_bic - convert iocontext queue structure to bfq_io_cq. * @icq: the iocontext queue. */ static struct bfq_io_cq *icq_to_bic(struct io_cq *icq) { /* bic->icq is the first member, %NULL will convert to %NULL */ return container_of(icq, struct bfq_io_cq, icq); } /** * bfq_bic_lookup - search into @ioc a bic associated to @bfqd. * @bfqd: the lookup key. * @ioc: the io_context of the process doing I/O. * @q: the request queue. */ static struct bfq_io_cq *bfq_bic_lookup(struct bfq_data *bfqd, struct io_context *ioc, struct request_queue *q) { if (ioc) { unsigned long flags; struct bfq_io_cq *icq; spin_lock_irqsave(q->queue_lock, flags); icq = icq_to_bic(ioc_lookup_icq(ioc, q)); spin_unlock_irqrestore(q->queue_lock, flags); return icq; } return NULL; } /* * Scheduler run of queue, if there are requests pending and no one in the * driver that will restart queueing. */ static void bfq_schedule_dispatch(struct bfq_data *bfqd) { if (bfqd->queued != 0) { bfq_log(bfqd, "schedule dispatch"); blk_mq_run_hw_queues(bfqd->queue, true); } } /* * Next two functions release bfqd->lock and put the io context * pointed by bfqd->ioc_to_put. This delayed put is used to not risk * to take an ioc->lock while the scheduler lock is being held. */ static void bfq_unlock_put_ioc(struct bfq_data *bfqd) { struct io_context *ioc_to_put = bfqd->ioc_to_put; bfqd->ioc_to_put = NULL; spin_unlock_irq(&bfqd->lock); if (ioc_to_put) put_io_context(ioc_to_put); } static void bfq_unlock_put_ioc_restore(struct bfq_data *bfqd, unsigned long flags) { struct io_context *ioc_to_put = bfqd->ioc_to_put; bfqd->ioc_to_put = NULL; spin_unlock_irqrestore(&bfqd->lock, flags); if (ioc_to_put) put_io_context(ioc_to_put); } /** * bfq_gt - compare two timestamps. * @a: first ts. * @b: second ts. * * Return @a > @b, dealing with wrapping correctly. */ static int bfq_gt(u64 a, u64 b) { return (s64)(a - b) > 0; } static struct bfq_entity *bfq_root_active_entity(struct rb_root *tree) { struct rb_node *node = tree->rb_node; return rb_entry(node, struct bfq_entity, rb_node); } static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd); static bool bfq_update_parent_budget(struct bfq_entity *next_in_service); /** * bfq_update_next_in_service - update sd->next_in_service * @sd: sched_data for which to perform the update. * @new_entity: if not NULL, pointer to the entity whose activation, * requeueing or repositionig triggered the invocation of * this function. * * This function is called to update sd->next_in_service, which, in * its turn, may change as a consequence of the insertion or * extraction of an entity into/from one of the active trees of * sd. These insertions/extractions occur as a consequence of * activations/deactivations of entities, with some activations being * 'true' activations, and other activations being requeueings (i.e., * implementing the second, requeueing phase of the mechanism used to * reposition an entity in its active tree; see comments on * __bfq_activate_entity and __bfq_requeue_entity for details). In * both the last two activation sub-cases, new_entity points to the * just activated or requeued entity. * * Returns true if sd->next_in_service changes in such a way that * entity->parent may become the next_in_service for its parent * entity. */ static bool bfq_update_next_in_service(struct bfq_sched_data *sd, struct bfq_entity *new_entity) { struct bfq_entity *next_in_service = sd->next_in_service; bool parent_sched_may_change = false; /* * If this update is triggered by the activation, requeueing * or repositiong of an entity that does not coincide with * sd->next_in_service, then a full lookup in the active tree * can be avoided. In fact, it is enough to check whether the * just-modified entity has a higher priority than * sd->next_in_service, or, even if it has the same priority * as sd->next_in_service, is eligible and has a lower virtual * finish time than sd->next_in_service. If this compound * condition holds, then the new entity becomes the new * next_in_service. Otherwise no change is needed. */ if (new_entity && new_entity != sd->next_in_service) { /* * Flag used to decide whether to replace * sd->next_in_service with new_entity. Tentatively * set to true, and left as true if * sd->next_in_service is NULL. */ bool replace_next = true; /* * If there is already a next_in_service candidate * entity, then compare class priorities or timestamps * to decide whether to replace sd->service_tree with * new_entity. */ if (next_in_service) { unsigned int new_entity_class_idx = bfq_class_idx(new_entity); struct bfq_service_tree *st = sd->service_tree + new_entity_class_idx; /* * For efficiency, evaluate the most likely * sub-condition first. */ replace_next = (new_entity_class_idx == bfq_class_idx(next_in_service) && !bfq_gt(new_entity->start, st->vtime) && bfq_gt(next_in_service->finish, new_entity->finish)) || new_entity_class_idx < bfq_class_idx(next_in_service); } if (replace_next) next_in_service = new_entity; } else /* invoked because of a deactivation: lookup needed */ next_in_service = bfq_lookup_next_entity(sd); if (next_in_service) { parent_sched_may_change = !sd->next_in_service || bfq_update_parent_budget(next_in_service); } sd->next_in_service = next_in_service; if (!next_in_service) return parent_sched_may_change; return parent_sched_may_change; } #ifdef CONFIG_BFQ_GROUP_IOSCHED /* both next loops stop at one of the child entities of the root group */ #define for_each_entity(entity) \ for (; entity ; entity = entity->parent) /* * For each iteration, compute parent in advance, so as to be safe if * entity is deallocated during the iteration. Such a deallocation may * happen as a consequence of a bfq_put_queue that frees the bfq_queue * containing entity. */ #define for_each_entity_safe(entity, parent) \ for (; entity && ({ parent = entity->parent; 1; }); entity = parent) /* * Returns true if this budget changes may let next_in_service->parent * become the next_in_service entity for its parent entity. */ static bool bfq_update_parent_budget(struct bfq_entity *next_in_service) { struct bfq_entity *bfqg_entity; struct bfq_group *bfqg; struct bfq_sched_data *group_sd; bool ret = false; group_sd = next_in_service->sched_data; bfqg = container_of(group_sd, struct bfq_group, sched_data); /* * bfq_group's my_entity field is not NULL only if the group * is not the root group. We must not touch the root entity * as it must never become an in-service entity. */ bfqg_entity = bfqg->my_entity; if (bfqg_entity) { if (bfqg_entity->budget > next_in_service->budget) ret = true; bfqg_entity->budget = next_in_service->budget; } return ret; } /* * This function tells whether entity stops being a candidate for next * service, according to the following logic. * * This function is invoked for an entity that is about to be set in * service. If such an entity is a queue, then the entity is no longer * a candidate for next service (i.e, a candidate entity to serve * after the in-service entity is expired). The function then returns * true. */ static bool bfq_no_longer_next_in_service(struct bfq_entity *entity) { if (bfq_entity_to_bfqq(entity)) return true; return false; } #else /* CONFIG_BFQ_GROUP_IOSCHED */ /* * Next two macros are fake loops when cgroups support is not * enabled. I fact, in such a case, there is only one level to go up * (to reach the root group). */ #define for_each_entity(entity) \ for (; entity ; entity = NULL) #define for_each_entity_safe(entity, parent) \ for (parent = NULL; entity ; entity = parent) static bool bfq_update_parent_budget(struct bfq_entity *next_in_service) { return false; } static bool bfq_no_longer_next_in_service(struct bfq_entity *entity) { return true; } #endif /* CONFIG_BFQ_GROUP_IOSCHED */ /* * Shift for timestamp calculations. This actually limits the maximum * service allowed in one timestamp delta (small shift values increase it), * the maximum total weight that can be used for the queues in the system * (big shift values increase it), and the period of virtual time * wraparounds. */ #define WFQ_SERVICE_SHIFT 22 static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity) { struct bfq_queue *bfqq = NULL; if (!entity->my_sched_data) bfqq = container_of(entity, struct bfq_queue, entity); return bfqq; } /** * bfq_delta - map service into the virtual time domain. * @service: amount of service. * @weight: scale factor (weight of an entity or weight sum). */ static u64 bfq_delta(unsigned long service, unsigned long weight) { u64 d = (u64)service << WFQ_SERVICE_SHIFT; do_div(d, weight); return d; } /** * bfq_calc_finish - assign the finish time to an entity. * @entity: the entity to act upon. * @service: the service to be charged to the entity. */ static void bfq_calc_finish(struct bfq_entity *entity, unsigned long service) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); entity->finish = entity->start + bfq_delta(service, entity->weight); if (bfqq) { bfq_log_bfqq(bfqq->bfqd, bfqq, "calc_finish: serv %lu, w %d", service, entity->weight); bfq_log_bfqq(bfqq->bfqd, bfqq, "calc_finish: start %llu, finish %llu, delta %llu", entity->start, entity->finish, bfq_delta(service, entity->weight)); } } /** * bfq_entity_of - get an entity from a node. * @node: the node field of the entity. * * Convert a node pointer to the relative entity. This is used only * to simplify the logic of some functions and not as the generic * conversion mechanism because, e.g., in the tree walking functions, * the check for a %NULL value would be redundant. */ static struct bfq_entity *bfq_entity_of(struct rb_node *node) { struct bfq_entity *entity = NULL; if (node) entity = rb_entry(node, struct bfq_entity, rb_node); return entity; } /** * bfq_extract - remove an entity from a tree. * @root: the tree root. * @entity: the entity to remove. */ static void bfq_extract(struct rb_root *root, struct bfq_entity *entity) { entity->tree = NULL; rb_erase(&entity->rb_node, root); } /** * bfq_idle_extract - extract an entity from the idle tree. * @st: the service tree of the owning @entity. * @entity: the entity being removed. */ static void bfq_idle_extract(struct bfq_service_tree *st, struct bfq_entity *entity) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); struct rb_node *next; if (entity == st->first_idle) { next = rb_next(&entity->rb_node); st->first_idle = bfq_entity_of(next); } if (entity == st->last_idle) { next = rb_prev(&entity->rb_node); st->last_idle = bfq_entity_of(next); } bfq_extract(&st->idle, entity); if (bfqq) list_del(&bfqq->bfqq_list); } /** * bfq_insert - generic tree insertion. * @root: tree root. * @entity: entity to insert. * * This is used for the idle and the active tree, since they are both * ordered by finish time. */ static void bfq_insert(struct rb_root *root, struct bfq_entity *entity) { struct bfq_entity *entry; struct rb_node **node = &root->rb_node; struct rb_node *parent = NULL; while (*node) { parent = *node; entry = rb_entry(parent, struct bfq_entity, rb_node); if (bfq_gt(entry->finish, entity->finish)) node = &parent->rb_left; else node = &parent->rb_right; } rb_link_node(&entity->rb_node, parent, node); rb_insert_color(&entity->rb_node, root); entity->tree = root; } /** * bfq_update_min - update the min_start field of a entity. * @entity: the entity to update. * @node: one of its children. * * This function is called when @entity may store an invalid value for * min_start due to updates to the active tree. The function assumes * that the subtree rooted at @node (which may be its left or its right * child) has a valid min_start value. */ static void bfq_update_min(struct bfq_entity *entity, struct rb_node *node) { struct bfq_entity *child; if (node) { child = rb_entry(node, struct bfq_entity, rb_node); if (bfq_gt(entity->min_start, child->min_start)) entity->min_start = child->min_start; } } /** * bfq_update_active_node - recalculate min_start. * @node: the node to update. * * @node may have changed position or one of its children may have moved, * this function updates its min_start value. The left and right subtrees * are assumed to hold a correct min_start value. */ static void bfq_update_active_node(struct rb_node *node) { struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node); entity->min_start = entity->start; bfq_update_min(entity, node->rb_right); bfq_update_min(entity, node->rb_left); } /** * bfq_update_active_tree - update min_start for the whole active tree. * @node: the starting node. * * @node must be the deepest modified node after an update. This function * updates its min_start using the values held by its children, assuming * that they did not change, and then updates all the nodes that may have * changed in the path to the root. The only nodes that may have changed * are the ones in the path or their siblings. */ static void bfq_update_active_tree(struct rb_node *node) { struct rb_node *parent; up: bfq_update_active_node(node); parent = rb_parent(node); if (!parent) return; if (node == parent->rb_left && parent->rb_right) bfq_update_active_node(parent->rb_right); else if (parent->rb_left) bfq_update_active_node(parent->rb_left); node = parent; goto up; } /** * bfq_active_insert - insert an entity in the active tree of its * group/device. * @st: the service tree of the entity. * @entity: the entity being inserted. * * The active tree is ordered by finish time, but an extra key is kept * per each node, containing the minimum value for the start times of * its children (and the node itself), so it's possible to search for * the eligible node with the lowest finish time in logarithmic time. */ static void bfq_active_insert(struct bfq_service_tree *st, struct bfq_entity *entity) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); struct rb_node *node = &entity->rb_node; #ifdef CONFIG_BFQ_GROUP_IOSCHED struct bfq_sched_data *sd = NULL; struct bfq_group *bfqg = NULL; struct bfq_data *bfqd = NULL; #endif bfq_insert(&st->active, entity); if (node->rb_left) node = node->rb_left; else if (node->rb_right) node = node->rb_right; bfq_update_active_tree(node); #ifdef CONFIG_BFQ_GROUP_IOSCHED sd = entity->sched_data; bfqg = container_of(sd, struct bfq_group, sched_data); bfqd = (struct bfq_data *)bfqg->bfqd; #endif if (bfqq) list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list); } /** * bfq_ioprio_to_weight - calc a weight from an ioprio. * @ioprio: the ioprio value to convert. */ static unsigned short bfq_ioprio_to_weight(int ioprio) { return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF; } /** * bfq_weight_to_ioprio - calc an ioprio from a weight. * @weight: the weight value to convert. * * To preserve as much as possible the old only-ioprio user interface, * 0 is used as an escape ioprio value for weights (numerically) equal or * larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF. */ static unsigned short bfq_weight_to_ioprio(int weight) { return max_t(int, 0, IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight); } static void bfq_get_entity(struct bfq_entity *entity) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); if (bfqq) { bfqq->ref++; bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d", bfqq, bfqq->ref); } } /** * bfq_find_deepest - find the deepest node that an extraction can modify. * @node: the node being removed. * * Do the first step of an extraction in an rb tree, looking for the * node that will replace @node, and returning the deepest node that * the following modifications to the tree can touch. If @node is the * last node in the tree return %NULL. */ static struct rb_node *bfq_find_deepest(struct rb_node *node) { struct rb_node *deepest; if (!node->rb_right && !node->rb_left) deepest = rb_parent(node); else if (!node->rb_right) deepest = node->rb_left; else if (!node->rb_left) deepest = node->rb_right; else { deepest = rb_next(node); if (deepest->rb_right) deepest = deepest->rb_right; else if (rb_parent(deepest) != node) deepest = rb_parent(deepest); } return deepest; } /** * bfq_active_extract - remove an entity from the active tree. * @st: the service_tree containing the tree. * @entity: the entity being removed. */ static void bfq_active_extract(struct bfq_service_tree *st, struct bfq_entity *entity) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); struct rb_node *node; #ifdef CONFIG_BFQ_GROUP_IOSCHED struct bfq_sched_data *sd = NULL; struct bfq_group *bfqg = NULL; struct bfq_data *bfqd = NULL; #endif node = bfq_find_deepest(&entity->rb_node); bfq_extract(&st->active, entity); if (node) bfq_update_active_tree(node); #ifdef CONFIG_BFQ_GROUP_IOSCHED sd = entity->sched_data; bfqg = container_of(sd, struct bfq_group, sched_data); bfqd = (struct bfq_data *)bfqg->bfqd; #endif if (bfqq) list_del(&bfqq->bfqq_list); } /** * bfq_idle_insert - insert an entity into the idle tree. * @st: the service tree containing the tree. * @entity: the entity to insert. */ static void bfq_idle_insert(struct bfq_service_tree *st, struct bfq_entity *entity) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); struct bfq_entity *first_idle = st->first_idle; struct bfq_entity *last_idle = st->last_idle; if (!first_idle || bfq_gt(first_idle->finish, entity->finish)) st->first_idle = entity; if (!last_idle || bfq_gt(entity->finish, last_idle->finish)) st->last_idle = entity; bfq_insert(&st->idle, entity); if (bfqq) list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list); } /** * bfq_forget_entity - do not consider entity any longer for scheduling * @st: the service tree. * @entity: the entity being removed. * @is_in_service: true if entity is currently the in-service entity. * * Forget everything about @entity. In addition, if entity represents * a queue, and the latter is not in service, then release the service * reference to the queue (the one taken through bfq_get_entity). In * fact, in this case, there is really no more service reference to * the queue, as the latter is also outside any service tree. If, * instead, the queue is in service, then __bfq_bfqd_reset_in_service * will take care of putting the reference when the queue finally * stops being served. */ static void bfq_forget_entity(struct bfq_service_tree *st, struct bfq_entity *entity, bool is_in_service) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); entity->on_st = false; st->wsum -= entity->weight; if (bfqq && !is_in_service) bfq_put_queue(bfqq); } /** * bfq_put_idle_entity - release the idle tree ref of an entity. * @st: service tree for the entity. * @entity: the entity being released. */ static void bfq_put_idle_entity(struct bfq_service_tree *st, struct bfq_entity *entity) { bfq_idle_extract(st, entity); bfq_forget_entity(st, entity, entity == entity->sched_data->in_service_entity); } /** * bfq_forget_idle - update the idle tree if necessary. * @st: the service tree to act upon. * * To preserve the global O(log N) complexity we only remove one entry here; * as the idle tree will not grow indefinitely this can be done safely. */ static void bfq_forget_idle(struct bfq_service_tree *st) { struct bfq_entity *first_idle = st->first_idle; struct bfq_entity *last_idle = st->last_idle; if (RB_EMPTY_ROOT(&st->active) && last_idle && !bfq_gt(last_idle->finish, st->vtime)) { /* * Forget the whole idle tree, increasing the vtime past * the last finish time of idle entities. */ st->vtime = last_idle->finish; } if (first_idle && !bfq_gt(first_idle->finish, st->vtime)) bfq_put_idle_entity(st, first_idle); } static struct bfq_service_tree * __bfq_entity_update_weight_prio(struct bfq_service_tree *old_st, struct bfq_entity *entity) { struct bfq_service_tree *new_st = old_st; if (entity->prio_changed) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); unsigned int prev_weight, new_weight; struct bfq_data *bfqd = NULL; #ifdef CONFIG_BFQ_GROUP_IOSCHED struct bfq_sched_data *sd; struct bfq_group *bfqg; #endif if (bfqq) bfqd = bfqq->bfqd; #ifdef CONFIG_BFQ_GROUP_IOSCHED else { sd = entity->my_sched_data; bfqg = container_of(sd, struct bfq_group, sched_data); bfqd = (struct bfq_data *)bfqg->bfqd; } #endif old_st->wsum -= entity->weight; if (entity->new_weight != entity->orig_weight) { if (entity->new_weight < BFQ_MIN_WEIGHT || entity->new_weight > BFQ_MAX_WEIGHT) { pr_crit("update_weight_prio: new_weight %d\n", entity->new_weight); if (entity->new_weight < BFQ_MIN_WEIGHT) entity->new_weight = BFQ_MIN_WEIGHT; else entity->new_weight = BFQ_MAX_WEIGHT; } entity->orig_weight = entity->new_weight; if (bfqq) bfqq->ioprio = bfq_weight_to_ioprio(entity->orig_weight); } if (bfqq) bfqq->ioprio_class = bfqq->new_ioprio_class; entity->prio_changed = 0; /* * NOTE: here we may be changing the weight too early, * this will cause unfairness. The correct approach * would have required additional complexity to defer * weight changes to the proper time instants (i.e., * when entity->finish <= old_st->vtime). */ new_st = bfq_entity_service_tree(entity); prev_weight = entity->weight; new_weight = entity->orig_weight * (bfqq ? bfqq->wr_coeff : 1); entity->weight = new_weight; new_st->wsum += entity->weight; if (new_st != old_st) entity->start = new_st->vtime; } return new_st; } static void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg); static struct bfq_group *bfqq_group(struct bfq_queue *bfqq); /** * bfq_bfqq_served - update the scheduler status after selection for * service. * @bfqq: the queue being served. * @served: bytes to transfer. * * NOTE: this can be optimized, as the timestamps of upper level entities * are synchronized every time a new bfqq is selected for service. By now, * we keep it to better check consistency. */ static void bfq_bfqq_served(struct bfq_queue *bfqq, int served) { struct bfq_entity *entity = &bfqq->entity; struct bfq_service_tree *st; for_each_entity(entity) { st = bfq_entity_service_tree(entity); entity->service += served; st->vtime += bfq_delta(served, st->wsum); bfq_forget_idle(st); } bfqg_stats_set_start_empty_time(bfqq_group(bfqq)); bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %d secs", served); } /** * bfq_bfqq_charge_time - charge an amount of service equivalent to the length * of the time interval during which bfqq has been in * service. * @bfqd: the device * @bfqq: the queue that needs a service update. * @time_ms: the amount of time during which the queue has received service * * If a queue does not consume its budget fast enough, then providing * the queue with service fairness may impair throughput, more or less * severely. For this reason, queues that consume their budget slowly * are provided with time fairness instead of service fairness. This * goal is achieved through the BFQ scheduling engine, even if such an * engine works in the service, and not in the time domain. The trick * is charging these queues with an inflated amount of service, equal * to the amount of service that they would have received during their * service slot if they had been fast, i.e., if their requests had * been dispatched at a rate equal to the estimated peak rate. * * It is worth noting that time fairness can cause important * distortions in terms of bandwidth distribution, on devices with * internal queueing. The reason is that I/O requests dispatched * during the service slot of a queue may be served after that service * slot is finished, and may have a total processing time loosely * correlated with the duration of the service slot. This is * especially true for short service slots. */ static void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq, unsigned long time_ms) { struct bfq_entity *entity = &bfqq->entity; int tot_serv_to_charge = entity->service; unsigned int timeout_ms = jiffies_to_msecs(bfq_timeout); if (time_ms > 0 && time_ms < timeout_ms) tot_serv_to_charge = (bfqd->bfq_max_budget * time_ms) / timeout_ms; if (tot_serv_to_charge < entity->service) tot_serv_to_charge = entity->service; /* Increase budget to avoid inconsistencies */ if (tot_serv_to_charge > entity->budget) entity->budget = tot_serv_to_charge; bfq_bfqq_served(bfqq, max_t(int, 0, tot_serv_to_charge - entity->service)); } static void bfq_update_fin_time_enqueue(struct bfq_entity *entity, struct bfq_service_tree *st, bool backshifted) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); st = __bfq_entity_update_weight_prio(st, entity); bfq_calc_finish(entity, entity->budget); /* * If some queues enjoy backshifting for a while, then their * (virtual) finish timestamps may happen to become lower and * lower than the system virtual time. In particular, if * these queues often happen to be idle for short time * periods, and during such time periods other queues with * higher timestamps happen to be busy, then the backshifted * timestamps of the former queues can become much lower than * the system virtual time. In fact, to serve the queues with * higher timestamps while the ones with lower timestamps are * idle, the system virtual time may be pushed-up to much * higher values than the finish timestamps of the idle * queues. As a consequence, the finish timestamps of all new * or newly activated queues may end up being much larger than * those of lucky queues with backshifted timestamps. The * latter queues may then monopolize the device for a lot of * time. This would simply break service guarantees. * * To reduce this problem, push up a little bit the * backshifted timestamps of the queue associated with this * entity (only a queue can happen to have the backshifted * flag set): just enough to let the finish timestamp of the * queue be equal to the current value of the system virtual * time. This may introduce a little unfairness among queues * with backshifted timestamps, but it does not break * worst-case fairness guarantees. * * As a special case, if bfqq is weight-raised, push up * timestamps much less, to keep very low the probability that * this push up causes the backshifted finish timestamps of * weight-raised queues to become higher than the backshifted * finish timestamps of non weight-raised queues. */ if (backshifted && bfq_gt(st->vtime, entity->finish)) { unsigned long delta = st->vtime - entity->finish; if (bfqq) delta /= bfqq->wr_coeff; entity->start += delta; entity->finish += delta; } bfq_active_insert(st, entity); } /** * __bfq_activate_entity - handle activation of entity. * @entity: the entity being activated. * @non_blocking_wait_rq: true if entity was waiting for a request * * Called for a 'true' activation, i.e., if entity is not active and * one of its children receives a new request. * * Basically, this function updates the timestamps of entity and * inserts entity into its active tree, ater possible extracting it * from its idle tree. */ static void __bfq_activate_entity(struct bfq_entity *entity, bool non_blocking_wait_rq) { struct bfq_service_tree *st = bfq_entity_service_tree(entity); bool backshifted = false; unsigned long long min_vstart; /* See comments on bfq_fqq_update_budg_for_activation */ if (non_blocking_wait_rq && bfq_gt(st->vtime, entity->finish)) { backshifted = true; min_vstart = entity->finish; } else min_vstart = st->vtime; if (entity->tree == &st->idle) { /* * Must be on the idle tree, bfq_idle_extract() will * check for that. */ bfq_idle_extract(st, entity); entity->start = bfq_gt(min_vstart, entity->finish) ? min_vstart : entity->finish; } else { /* * The finish time of the entity may be invalid, and * it is in the past for sure, otherwise the queue * would have been on the idle tree. */ entity->start = min_vstart; st->wsum += entity->weight; /* * entity is about to be inserted into a service tree, * and then set in service: get a reference to make * sure entity does not disappear until it is no * longer in service or scheduled for service. */ bfq_get_entity(entity); entity->on_st = true; } bfq_update_fin_time_enqueue(entity, st, backshifted); } /** * __bfq_requeue_entity - handle requeueing or repositioning of an entity. * @entity: the entity being requeued or repositioned. * * Requeueing is needed if this entity stops being served, which * happens if a leaf descendant entity has expired. On the other hand, * repositioning is needed if the next_inservice_entity for the child * entity has changed. See the comments inside the function for * details. * * Basically, this function: 1) removes entity from its active tree if * present there, 2) updates the timestamps of entity and 3) inserts * entity back into its active tree (in the new, right position for * the new values of the timestamps). */ static void __bfq_requeue_entity(struct bfq_entity *entity) { struct bfq_sched_data *sd = entity->sched_data; struct bfq_service_tree *st = bfq_entity_service_tree(entity); if (entity == sd->in_service_entity) { /* * We are requeueing the current in-service entity, * which may have to be done for one of the following * reasons: * - entity represents the in-service queue, and the * in-service queue is being requeued after an * expiration; * - entity represents a group, and its budget has * changed because one of its child entities has * just been either activated or requeued for some * reason; the timestamps of the entity need then to * be updated, and the entity needs to be enqueued * or repositioned accordingly. * * In particular, before requeueing, the start time of * the entity must be moved forward to account for the * service that the entity has received while in * service. This is done by the next instructions. The * finish time will then be updated according to this * new value of the start time, and to the budget of * the entity. */ bfq_calc_finish(entity, entity->service); entity->start = entity->finish; /* * In addition, if the entity had more than one child * when set in service, then was not extracted from * the active tree. This implies that the position of * the entity in the active tree may need to be * changed now, because we have just updated the start * time of the entity, and we will update its finish * time in a moment (the requeueing is then, more * precisely, a repositioning in this case). To * implement this repositioning, we: 1) dequeue the * entity here, 2) update the finish time and * requeue the entity according to the new * timestamps below. */ if (entity->tree) bfq_active_extract(st, entity); } else { /* The entity is already active, and not in service */ /* * In this case, this function gets called only if the * next_in_service entity below this entity has * changed, and this change has caused the budget of * this entity to change, which, finally implies that * the finish time of this entity must be * updated. Such an update may cause the scheduling, * i.e., the position in the active tree, of this * entity to change. We handle this change by: 1) * dequeueing the entity here, 2) updating the finish * time and requeueing the entity according to the new * timestamps below. This is the same approach as the * non-extracted-entity sub-case above. */ bfq_active_extract(st, entity); } bfq_update_fin_time_enqueue(entity, st, false); } static void __bfq_activate_requeue_entity(struct bfq_entity *entity, struct bfq_sched_data *sd, bool non_blocking_wait_rq) { struct bfq_service_tree *st = bfq_entity_service_tree(entity); if (sd->in_service_entity == entity || entity->tree == &st->active) /* * in service or already queued on the active tree, * requeue or reposition */ __bfq_requeue_entity(entity); else /* * Not in service and not queued on its active tree: * the activity is idle and this is a true activation. */ __bfq_activate_entity(entity, non_blocking_wait_rq); } /** * bfq_activate_entity - activate or requeue an entity representing a bfq_queue, * and activate, requeue or reposition all ancestors * for which such an update becomes necessary. * @entity: the entity to activate. * @non_blocking_wait_rq: true if this entity was waiting for a request * @requeue: true if this is a requeue, which implies that bfqq is * being expired; thus ALL its ancestors stop being served and must * therefore be requeued */ static void bfq_activate_requeue_entity(struct bfq_entity *entity, bool non_blocking_wait_rq, bool requeue) { struct bfq_sched_data *sd; for_each_entity(entity) { sd = entity->sched_data; __bfq_activate_requeue_entity(entity, sd, non_blocking_wait_rq); if (!bfq_update_next_in_service(sd, entity) && !requeue) break; } } /** * __bfq_deactivate_entity - deactivate an entity from its service tree. * @entity: the entity to deactivate. * @ins_into_idle_tree: if false, the entity will not be put into the * idle tree. * * Deactivates an entity, independently from its previous state. Must * be invoked only if entity is on a service tree. Extracts the entity * from that tree, and if necessary and allowed, puts it on the idle * tree. */ static bool __bfq_deactivate_entity(struct bfq_entity *entity, bool ins_into_idle_tree) { struct bfq_sched_data *sd = entity->sched_data; struct bfq_service_tree *st = bfq_entity_service_tree(entity); int is_in_service = entity == sd->in_service_entity; if (!entity->on_st) /* entity never activated, or already inactive */ return false; if (is_in_service) bfq_calc_finish(entity, entity->service); if (entity->tree == &st->active) bfq_active_extract(st, entity); else if (!is_in_service && entity->tree == &st->idle) bfq_idle_extract(st, entity); if (!ins_into_idle_tree || !bfq_gt(entity->finish, st->vtime)) bfq_forget_entity(st, entity, is_in_service); else bfq_idle_insert(st, entity); return true; } /** * bfq_deactivate_entity - deactivate an entity representing a bfq_queue. * @entity: the entity to deactivate. * @ins_into_idle_tree: true if the entity can be put on the idle tree */ static void bfq_deactivate_entity(struct bfq_entity *entity, bool ins_into_idle_tree, bool expiration) { struct bfq_sched_data *sd; struct bfq_entity *parent = NULL; for_each_entity_safe(entity, parent) { sd = entity->sched_data; if (!__bfq_deactivate_entity(entity, ins_into_idle_tree)) { /* * entity is not in any tree any more, so * this deactivation is a no-op, and there is * nothing to change for upper-level entities * (in case of expiration, this can never * happen). */ return; } if (sd->next_in_service == entity) /* * entity was the next_in_service entity, * then, since entity has just been * deactivated, a new one must be found. */ bfq_update_next_in_service(sd, NULL); if (sd->next_in_service) /* * The parent entity is still backlogged, * because next_in_service is not NULL. So, no * further upwards deactivation must be * performed. Yet, next_in_service has * changed. Then the schedule does need to be * updated upwards. */ break; /* * If we get here, then the parent is no more * backlogged and we need to propagate the * deactivation upwards. Thus let the loop go on. */ /* * Also let parent be queued into the idle tree on * deactivation, to preserve service guarantees, and * assuming that who invoked this function does not * need parent entities too to be removed completely. */ ins_into_idle_tree = true; } /* * If the deactivation loop is fully executed, then there are * no more entities to touch and next loop is not executed at * all. Otherwise, requeue remaining entities if they are * about to stop receiving service, or reposition them if this * is not the case. */ entity = parent; for_each_entity(entity) { /* * Invoke __bfq_requeue_entity on entity, even if * already active, to requeue/reposition it in the * active tree (because sd->next_in_service has * changed) */ __bfq_requeue_entity(entity); sd = entity->sched_data; if (!bfq_update_next_in_service(sd, entity) && !expiration) /* * next_in_service unchanged or not causing * any change in entity->parent->sd, and no * requeueing needed for expiration: stop * here. */ break; } } /** * bfq_calc_vtime_jump - compute the value to which the vtime should jump, * if needed, to have at least one entity eligible. * @st: the service tree to act upon. * * Assumes that st is not empty. */ static u64 bfq_calc_vtime_jump(struct bfq_service_tree *st) { struct bfq_entity *root_entity = bfq_root_active_entity(&st->active); if (bfq_gt(root_entity->min_start, st->vtime)) return root_entity->min_start; return st->vtime; } static void bfq_update_vtime(struct bfq_service_tree *st, u64 new_value) { if (new_value > st->vtime) { st->vtime = new_value; bfq_forget_idle(st); } } /** * bfq_first_active_entity - find the eligible entity with * the smallest finish time * @st: the service tree to select from. * @vtime: the system virtual to use as a reference for eligibility * * This function searches the first schedulable entity, starting from the * root of the tree and going on the left every time on this side there is * a subtree with at least one eligible (start >= vtime) entity. The path on * the right is followed only if a) the left subtree contains no eligible * entities and b) no eligible entity has been found yet. */ static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st, u64 vtime) { struct bfq_entity *entry, *first = NULL; struct rb_node *node = st->active.rb_node; while (node) { entry = rb_entry(node, struct bfq_entity, rb_node); left: if (!bfq_gt(entry->start, vtime)) first = entry; if (node->rb_left) { entry = rb_entry(node->rb_left, struct bfq_entity, rb_node); if (!bfq_gt(entry->min_start, vtime)) { node = node->rb_left; goto left; } } if (first) break; node = node->rb_right; } return first; } /** * __bfq_lookup_next_entity - return the first eligible entity in @st. * @st: the service tree. * * If there is no in-service entity for the sched_data st belongs to, * then return the entity that will be set in service if: * 1) the parent entity this st belongs to is set in service; * 2) no entity belonging to such parent entity undergoes a state change * that would influence the timestamps of the entity (e.g., becomes idle, * becomes backlogged, changes its budget, ...). * * In this first case, update the virtual time in @st too (see the * comments on this update inside the function). * * In constrast, if there is an in-service entity, then return the * entity that would be set in service if not only the above * conditions, but also the next one held true: the currently * in-service entity, on expiration, * 1) gets a finish time equal to the current one, or * 2) is not eligible any more, or * 3) is idle. */ static struct bfq_entity * __bfq_lookup_next_entity(struct bfq_service_tree *st, bool in_service) { struct bfq_entity *entity; u64 new_vtime; if (RB_EMPTY_ROOT(&st->active)) return NULL; /* * Get the value of the system virtual time for which at * least one entity is eligible. */ new_vtime = bfq_calc_vtime_jump(st); /* * If there is no in-service entity for the sched_data this * active tree belongs to, then push the system virtual time * up to the value that guarantees that at least one entity is * eligible. If, instead, there is an in-service entity, then * do not make any such update, because there is already an * eligible entity, namely the in-service one (even if the * entity is not on st, because it was extracted when set in * service). */ if (!in_service) bfq_update_vtime(st, new_vtime); entity = bfq_first_active_entity(st, new_vtime); return entity; } /** * bfq_lookup_next_entity - return the first eligible entity in @sd. * @sd: the sched_data. * * This function is invoked when there has been a change in the trees * for sd, and we need know what is the new next entity after this * change. */ static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd) { struct bfq_service_tree *st = sd->service_tree; struct bfq_service_tree *idle_class_st = st + (BFQ_IOPRIO_CLASSES - 1); struct bfq_entity *entity = NULL; int class_idx = 0; /* * Choose from idle class, if needed to guarantee a minimum * bandwidth to this class (and if there is some active entity * in idle class). This should also mitigate * priority-inversion problems in case a low priority task is * holding file system resources. */ if (time_is_before_jiffies(sd->bfq_class_idle_last_service + BFQ_CL_IDLE_TIMEOUT)) { if (!RB_EMPTY_ROOT(&idle_class_st->active)) class_idx = BFQ_IOPRIO_CLASSES - 1; /* About to be served if backlogged, or not yet backlogged */ sd->bfq_class_idle_last_service = jiffies; } /* * Find the next entity to serve for the highest-priority * class, unless the idle class needs to be served. */ for (; class_idx < BFQ_IOPRIO_CLASSES; class_idx++) { entity = __bfq_lookup_next_entity(st + class_idx, sd->in_service_entity); if (entity) break; } if (!entity) return NULL; return entity; } static bool next_queue_may_preempt(struct bfq_data *bfqd) { struct bfq_sched_data *sd = &bfqd->root_group->sched_data; return sd->next_in_service != sd->in_service_entity; } /* * Get next queue for service. */ static struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd) { struct bfq_entity *entity = NULL; struct bfq_sched_data *sd; struct bfq_queue *bfqq; if (bfqd->busy_queues == 0) return NULL; /* * Traverse the path from the root to the leaf entity to * serve. Set in service all the entities visited along the * way. */ sd = &bfqd->root_group->sched_data; for (; sd ; sd = entity->my_sched_data) { /* * WARNING. We are about to set the in-service entity * to sd->next_in_service, i.e., to the (cached) value * returned by bfq_lookup_next_entity(sd) the last * time it was invoked, i.e., the last time when the * service order in sd changed as a consequence of the * activation or deactivation of an entity. In this * respect, if we execute bfq_lookup_next_entity(sd) * in this very moment, it may, although with low * probability, yield a different entity than that * pointed to by sd->next_in_service. This rare event * happens in case there was no CLASS_IDLE entity to * serve for sd when bfq_lookup_next_entity(sd) was * invoked for the last time, while there is now one * such entity. * * If the above event happens, then the scheduling of * such entity in CLASS_IDLE is postponed until the * service of the sd->next_in_service entity * finishes. In fact, when the latter is expired, * bfq_lookup_next_entity(sd) gets called again, * exactly to update sd->next_in_service. */ /* Make next_in_service entity become in_service_entity */ entity = sd->next_in_service; sd->in_service_entity = entity; /* * Reset the accumulator of the amount of service that * the entity is about to receive. */ entity->service = 0; /* * If entity is no longer a candidate for next * service, then we extract it from its active tree, * for the following reason. To further boost the * throughput in some special case, BFQ needs to know * which is the next candidate entity to serve, while * there is already an entity in service. In this * respect, to make it easy to compute/update the next * candidate entity to serve after the current * candidate has been set in service, there is a case * where it is necessary to extract the current * candidate from its service tree. Such a case is * when the entity just set in service cannot be also * a candidate for next service. Details about when * this conditions holds are reported in the comments * on the function bfq_no_longer_next_in_service() * invoked below. */ if (bfq_no_longer_next_in_service(entity)) bfq_active_extract(bfq_entity_service_tree(entity), entity); /* * For the same reason why we may have just extracted * entity from its active tree, we may need to update * next_in_service for the sched_data of entity too, * regardless of whether entity has been extracted. * In fact, even if entity has not been extracted, a * descendant entity may get extracted. Such an event * would cause a change in next_in_service for the * level of the descendant entity, and thus possibly * back to upper levels. * * We cannot perform the resulting needed update * before the end of this loop, because, to know which * is the correct next-to-serve candidate entity for * each level, we need first to find the leaf entity * to set in service. In fact, only after we know * which is the next-to-serve leaf entity, we can * discover whether the parent entity of the leaf * entity becomes the next-to-serve, and so on. */ } bfqq = bfq_entity_to_bfqq(entity); /* * We can finally update all next-to-serve entities along the * path from the leaf entity just set in service to the root. */ for_each_entity(entity) { struct bfq_sched_data *sd = entity->sched_data; if (!bfq_update_next_in_service(sd, NULL)) break; } return bfqq; } static void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd) { struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue; struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity; struct bfq_entity *entity = in_serv_entity; if (bfqd->in_service_bic) { /* * Schedule the release of a reference to * bfqd->in_service_bic->icq.ioc to right after the * scheduler lock is released. This ioc is not * released immediately, to not risk to possibly take * an ioc->lock while holding the scheduler lock. */ bfqd->ioc_to_put = bfqd->in_service_bic->icq.ioc; bfqd->in_service_bic = NULL; } bfq_clear_bfqq_wait_request(in_serv_bfqq); hrtimer_try_to_cancel(&bfqd->idle_slice_timer); bfqd->in_service_queue = NULL; /* * When this function is called, all in-service entities have * been properly deactivated or requeued, so we can safely * execute the final step: reset in_service_entity along the * path from entity to the root. */ for_each_entity(entity) entity->sched_data->in_service_entity = NULL; /* * in_serv_entity is no longer in service, so, if it is in no * service tree either, then release the service reference to * the queue it represents (taken with bfq_get_entity). */ if (!in_serv_entity->on_st) bfq_put_queue(in_serv_bfqq); } static void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, bool ins_into_idle_tree, bool expiration) { struct bfq_entity *entity = &bfqq->entity; bfq_deactivate_entity(entity, ins_into_idle_tree, expiration); } static void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) { struct bfq_entity *entity = &bfqq->entity; bfq_activate_requeue_entity(entity, bfq_bfqq_non_blocking_wait_rq(bfqq), false); bfq_clear_bfqq_non_blocking_wait_rq(bfqq); } static void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) { struct bfq_entity *entity = &bfqq->entity; bfq_activate_requeue_entity(entity, false, bfqq == bfqd->in_service_queue); } static void bfqg_stats_update_dequeue(struct bfq_group *bfqg); /* * Called when the bfqq no longer has requests pending, remove it from * the service tree. As a special case, it can be invoked during an * expiration. */ static void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq, bool expiration) { bfq_log_bfqq(bfqd, bfqq, "del from busy"); bfq_clear_bfqq_busy(bfqq); bfqd->busy_queues--; if (bfqq->wr_coeff > 1) bfqd->wr_busy_queues--; bfqg_stats_update_dequeue(bfqq_group(bfqq)); bfq_deactivate_bfqq(bfqd, bfqq, true, expiration); } /* * Called when an inactive queue receives a new request. */ static void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq) { bfq_log_bfqq(bfqd, bfqq, "add to busy"); bfq_activate_bfqq(bfqd, bfqq); bfq_mark_bfqq_busy(bfqq); bfqd->busy_queues++; if (bfqq->wr_coeff > 1) bfqd->wr_busy_queues++; } #ifdef CONFIG_BFQ_GROUP_IOSCHED /* bfqg stats flags */ enum bfqg_stats_flags { BFQG_stats_waiting = 0, BFQG_stats_idling, BFQG_stats_empty, }; #define BFQG_FLAG_FNS(name) \ static void bfqg_stats_mark_##name(struct bfqg_stats *stats) \ { \ stats->flags |= (1 << BFQG_stats_##name); \ } \ static void bfqg_stats_clear_##name(struct bfqg_stats *stats) \ { \ stats->flags &= ~(1 << BFQG_stats_##name); \ } \ static int bfqg_stats_##name(struct bfqg_stats *stats) \ { \ return (stats->flags & (1 << BFQG_stats_##name)) != 0; \ } \ BFQG_FLAG_FNS(waiting) BFQG_FLAG_FNS(idling) BFQG_FLAG_FNS(empty) #undef BFQG_FLAG_FNS /* This should be called with the queue_lock held. */ static void bfqg_stats_update_group_wait_time(struct bfqg_stats *stats) { unsigned long long now; if (!bfqg_stats_waiting(stats)) return; now = sched_clock(); if (time_after64(now, stats->start_group_wait_time)) blkg_stat_add(&stats->group_wait_time, now - stats->start_group_wait_time); bfqg_stats_clear_waiting(stats); } /* This should be called with the queue_lock held. */ static void bfqg_stats_set_start_group_wait_time(struct bfq_group *bfqg, struct bfq_group *curr_bfqg) { struct bfqg_stats *stats = &bfqg->stats; if (bfqg_stats_waiting(stats)) return; if (bfqg == curr_bfqg) return; stats->start_group_wait_time = sched_clock(); bfqg_stats_mark_waiting(stats); } /* This should be called with the queue_lock held. */ static void bfqg_stats_end_empty_time(struct bfqg_stats *stats) { unsigned long long now; if (!bfqg_stats_empty(stats)) return; now = sched_clock(); if (time_after64(now, stats->start_empty_time)) blkg_stat_add(&stats->empty_time, now - stats->start_empty_time); bfqg_stats_clear_empty(stats); } static void bfqg_stats_update_dequeue(struct bfq_group *bfqg) { blkg_stat_add(&bfqg->stats.dequeue, 1); } static void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg) { struct bfqg_stats *stats = &bfqg->stats; if (blkg_rwstat_total(&stats->queued)) return; /* * group is already marked empty. This can happen if bfqq got new * request in parent group and moved to this group while being added * to service tree. Just ignore the event and move on. */ if (bfqg_stats_empty(stats)) return; stats->start_empty_time = sched_clock(); bfqg_stats_mark_empty(stats); } static void bfqg_stats_update_idle_time(struct bfq_group *bfqg) { struct bfqg_stats *stats = &bfqg->stats; if (bfqg_stats_idling(stats)) { unsigned long long now = sched_clock(); if (time_after64(now, stats->start_idle_time)) blkg_stat_add(&stats->idle_time, now - stats->start_idle_time); bfqg_stats_clear_idling(stats); } } static void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg) { struct bfqg_stats *stats = &bfqg->stats; stats->start_idle_time = sched_clock(); bfqg_stats_mark_idling(stats); } static void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg) { struct bfqg_stats *stats = &bfqg->stats; blkg_stat_add(&stats->avg_queue_size_sum, blkg_rwstat_total(&stats->queued)); blkg_stat_add(&stats->avg_queue_size_samples, 1); bfqg_stats_update_group_wait_time(stats); } /* * blk-cgroup policy-related handlers * The following functions help in converting between blk-cgroup * internal structures and BFQ-specific structures. */ static struct bfq_group *pd_to_bfqg(struct blkg_policy_data *pd) { return pd ? container_of(pd, struct bfq_group, pd) : NULL; } static struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg) { return pd_to_blkg(&bfqg->pd); } static struct blkcg_policy blkcg_policy_bfq; static struct bfq_group *blkg_to_bfqg(struct blkcg_gq *blkg) { return pd_to_bfqg(blkg_to_pd(blkg, &blkcg_policy_bfq)); } /* * bfq_group handlers * The following functions help in navigating the bfq_group hierarchy * by allowing to find the parent of a bfq_group or the bfq_group * associated to a bfq_queue. */ static struct bfq_group *bfqg_parent(struct bfq_group *bfqg) { struct blkcg_gq *pblkg = bfqg_to_blkg(bfqg)->parent; return pblkg ? blkg_to_bfqg(pblkg) : NULL; } static struct bfq_group *bfqq_group(struct bfq_queue *bfqq) { struct bfq_entity *group_entity = bfqq->entity.parent; return group_entity ? container_of(group_entity, struct bfq_group, entity) : bfqq->bfqd->root_group; } /* * The following two functions handle get and put of a bfq_group by * wrapping the related blk-cgroup hooks. */ static void bfqg_get(struct bfq_group *bfqg) { return blkg_get(bfqg_to_blkg(bfqg)); } static void bfqg_put(struct bfq_group *bfqg) { return blkg_put(bfqg_to_blkg(bfqg)); } static void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq, unsigned int op) { blkg_rwstat_add(&bfqg->stats.queued, op, 1); bfqg_stats_end_empty_time(&bfqg->stats); if (!(bfqq == ((struct bfq_data *)bfqg->bfqd)->in_service_queue)) bfqg_stats_set_start_group_wait_time(bfqg, bfqq_group(bfqq)); } static void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op) { blkg_rwstat_add(&bfqg->stats.queued, op, -1); } static void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op) { blkg_rwstat_add(&bfqg->stats.merged, op, 1); } static void bfqg_stats_update_completion(struct bfq_group *bfqg, uint64_t start_time, uint64_t io_start_time, unsigned int op) { struct bfqg_stats *stats = &bfqg->stats; unsigned long long now = sched_clock(); if (time_after64(now, io_start_time)) blkg_rwstat_add(&stats->service_time, op, now - io_start_time); if (time_after64(io_start_time, start_time)) blkg_rwstat_add(&stats->wait_time, op, io_start_time - start_time); } /* @stats = 0 */ static void bfqg_stats_reset(struct bfqg_stats *stats) { /* queued stats shouldn't be cleared */ blkg_rwstat_reset(&stats->merged); blkg_rwstat_reset(&stats->service_time); blkg_rwstat_reset(&stats->wait_time); blkg_stat_reset(&stats->time); blkg_stat_reset(&stats->avg_queue_size_sum); blkg_stat_reset(&stats->avg_queue_size_samples); blkg_stat_reset(&stats->dequeue); blkg_stat_reset(&stats->group_wait_time); blkg_stat_reset(&stats->idle_time); blkg_stat_reset(&stats->empty_time); } /* @to += @from */ static void bfqg_stats_add_aux(struct bfqg_stats *to, struct bfqg_stats *from) { if (!to || !from) return; /* queued stats shouldn't be cleared */ blkg_rwstat_add_aux(&to->merged, &from->merged); blkg_rwstat_add_aux(&to->service_time, &from->service_time); blkg_rwstat_add_aux(&to->wait_time, &from->wait_time); blkg_stat_add_aux(&from->time, &from->time); blkg_stat_add_aux(&to->avg_queue_size_sum, &from->avg_queue_size_sum); blkg_stat_add_aux(&to->avg_queue_size_samples, &from->avg_queue_size_samples); blkg_stat_add_aux(&to->dequeue, &from->dequeue); blkg_stat_add_aux(&to->group_wait_time, &from->group_wait_time); blkg_stat_add_aux(&to->idle_time, &from->idle_time); blkg_stat_add_aux(&to->empty_time, &from->empty_time); } /* * Transfer @bfqg's stats to its parent's aux counts so that the ancestors' * recursive stats can still account for the amount used by this bfqg after * it's gone. */ static void bfqg_stats_xfer_dead(struct bfq_group *bfqg) { struct bfq_group *parent; if (!bfqg) /* root_group */ return; parent = bfqg_parent(bfqg); lockdep_assert_held(bfqg_to_blkg(bfqg)->q->queue_lock); if (unlikely(!parent)) return; bfqg_stats_add_aux(&parent->stats, &bfqg->stats); bfqg_stats_reset(&bfqg->stats); } static void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); entity->weight = entity->new_weight; entity->orig_weight = entity->new_weight; if (bfqq) { bfqq->ioprio = bfqq->new_ioprio; bfqq->ioprio_class = bfqq->new_ioprio_class; bfqg_get(bfqg); } entity->parent = bfqg->my_entity; /* NULL for root group */ entity->sched_data = &bfqg->sched_data; } static void bfqg_stats_exit(struct bfqg_stats *stats) { blkg_rwstat_exit(&stats->merged); blkg_rwstat_exit(&stats->service_time); blkg_rwstat_exit(&stats->wait_time); blkg_rwstat_exit(&stats->queued); blkg_stat_exit(&stats->time); blkg_stat_exit(&stats->avg_queue_size_sum); blkg_stat_exit(&stats->avg_queue_size_samples); blkg_stat_exit(&stats->dequeue); blkg_stat_exit(&stats->group_wait_time); blkg_stat_exit(&stats->idle_time); blkg_stat_exit(&stats->empty_time); } static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp) { if (blkg_rwstat_init(&stats->merged, gfp) || blkg_rwstat_init(&stats->service_time, gfp) || blkg_rwstat_init(&stats->wait_time, gfp) || blkg_rwstat_init(&stats->queued, gfp) || blkg_stat_init(&stats->time, gfp) || blkg_stat_init(&stats->avg_queue_size_sum, gfp) || blkg_stat_init(&stats->avg_queue_size_samples, gfp) || blkg_stat_init(&stats->dequeue, gfp) || blkg_stat_init(&stats->group_wait_time, gfp) || blkg_stat_init(&stats->idle_time, gfp) || blkg_stat_init(&stats->empty_time, gfp)) { bfqg_stats_exit(stats); return -ENOMEM; } return 0; } static struct bfq_group_data *cpd_to_bfqgd(struct blkcg_policy_data *cpd) { return cpd ? container_of(cpd, struct bfq_group_data, pd) : NULL; } static struct bfq_group_data *blkcg_to_bfqgd(struct blkcg *blkcg) { return cpd_to_bfqgd(blkcg_to_cpd(blkcg, &blkcg_policy_bfq)); } static struct blkcg_policy_data *bfq_cpd_alloc(gfp_t gfp) { struct bfq_group_data *bgd; bgd = kzalloc(sizeof(*bgd), gfp); if (!bgd) return NULL; return &bgd->pd; } static void bfq_cpd_init(struct blkcg_policy_data *cpd) { struct bfq_group_data *d = cpd_to_bfqgd(cpd); d->weight = cgroup_subsys_on_dfl(io_cgrp_subsys) ? CGROUP_WEIGHT_DFL : BFQ_WEIGHT_LEGACY_DFL; } static void bfq_cpd_free(struct blkcg_policy_data *cpd) { kfree(cpd_to_bfqgd(cpd)); } static struct blkg_policy_data *bfq_pd_alloc(gfp_t gfp, int node) { struct bfq_group *bfqg; bfqg = kzalloc_node(sizeof(*bfqg), gfp, node); if (!bfqg) return NULL; if (bfqg_stats_init(&bfqg->stats, gfp)) { kfree(bfqg); return NULL; } return &bfqg->pd; } static void bfq_pd_init(struct blkg_policy_data *pd) { struct blkcg_gq *blkg = pd_to_blkg(pd); struct bfq_group *bfqg = blkg_to_bfqg(blkg); struct bfq_data *bfqd = blkg->q->elevator->elevator_data; struct bfq_entity *entity = &bfqg->entity; struct bfq_group_data *d = blkcg_to_bfqgd(blkg->blkcg); entity->orig_weight = entity->weight = entity->new_weight = d->weight; entity->my_sched_data = &bfqg->sched_data; bfqg->my_entity = entity; /* * the root_group's will be set to NULL * in bfq_init_queue() */ bfqg->bfqd = bfqd; bfqg->rq_pos_tree = RB_ROOT; } static void bfq_pd_free(struct blkg_policy_data *pd) { struct bfq_group *bfqg = pd_to_bfqg(pd); bfqg_stats_exit(&bfqg->stats); return kfree(bfqg); } static void bfq_pd_reset_stats(struct blkg_policy_data *pd) { struct bfq_group *bfqg = pd_to_bfqg(pd); bfqg_stats_reset(&bfqg->stats); } static void bfq_group_set_parent(struct bfq_group *bfqg, struct bfq_group *parent) { struct bfq_entity *entity; entity = &bfqg->entity; entity->parent = parent->my_entity; entity->sched_data = &parent->sched_data; } static struct bfq_group *bfq_lookup_bfqg(struct bfq_data *bfqd, struct blkcg *blkcg) { struct blkcg_gq *blkg; blkg = blkg_lookup(blkcg, bfqd->queue); if (likely(blkg)) return blkg_to_bfqg(blkg); return NULL; } static struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd, struct blkcg *blkcg) { struct bfq_group *bfqg, *parent; struct bfq_entity *entity; bfqg = bfq_lookup_bfqg(bfqd, blkcg); if (unlikely(!bfqg)) return NULL; /* * Update chain of bfq_groups as we might be handling a leaf group * which, along with some of its relatives, has not been hooked yet * to the private hierarchy of BFQ. */ entity = &bfqg->entity; for_each_entity(entity) { bfqg = container_of(entity, struct bfq_group, entity); if (bfqg != bfqd->root_group) { parent = bfqg_parent(bfqg); if (!parent) parent = bfqd->root_group; bfq_group_set_parent(bfqg, parent); } } return bfqg; } static void bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq); static void bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq, bool compensate, enum bfqq_expiration reason); /** * bfq_bfqq_move - migrate @bfqq to @bfqg. * @bfqd: queue descriptor. * @bfqq: the queue to move. * @bfqg: the group to move to. * * Move @bfqq to @bfqg, deactivating it from its old group and reactivating * it on the new one. Avoid putting the entity on the old group idle tree. * * Must be called under the queue lock; the cgroup owning @bfqg must * not disappear (by now this just means that we are called under * rcu_read_lock()). */ static void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct bfq_group *bfqg) { struct bfq_entity *entity = &bfqq->entity; /* If bfqq is empty, then bfq_bfqq_expire also invokes * bfq_del_bfqq_busy, thereby removing bfqq and its entity * from data structures related to current group. Otherwise we * need to remove bfqq explicitly with bfq_deactivate_bfqq, as * we do below. */ if (bfqq == bfqd->in_service_queue) bfq_bfqq_expire(bfqd, bfqd->in_service_queue, false, BFQQE_PREEMPTED); if (bfq_bfqq_busy(bfqq)) bfq_deactivate_bfqq(bfqd, bfqq, false, false); else if (entity->on_st) bfq_put_idle_entity(bfq_entity_service_tree(entity), entity); bfqg_put(bfqq_group(bfqq)); /* * Here we use a reference to bfqg. We don't need a refcounter * as the cgroup reference will not be dropped, so that its * destroy() callback will not be invoked. */ entity->parent = bfqg->my_entity; entity->sched_data = &bfqg->sched_data; bfqg_get(bfqg); if (bfq_bfqq_busy(bfqq)) { bfq_pos_tree_add_move(bfqd, bfqq); bfq_activate_bfqq(bfqd, bfqq); } if (!bfqd->in_service_queue && !bfqd->rq_in_driver) bfq_schedule_dispatch(bfqd); } /** * __bfq_bic_change_cgroup - move @bic to @cgroup. * @bfqd: the queue descriptor. * @bic: the bic to move. * @blkcg: the blk-cgroup to move to. * * Move bic to blkcg, assuming that bfqd->queue is locked; the caller * has to make sure that the reference to cgroup is valid across the call. * * NOTE: an alternative approach might have been to store the current * cgroup in bfqq and getting a reference to it, reducing the lookup * time here, at the price of slightly more complex code. */ static struct bfq_group *__bfq_bic_change_cgroup(struct bfq_data *bfqd, struct bfq_io_cq *bic, struct blkcg *blkcg) { struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0); struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1); struct bfq_group *bfqg; struct bfq_entity *entity; bfqg = bfq_find_set_group(bfqd, blkcg); if (unlikely(!bfqg)) bfqg = bfqd->root_group; if (async_bfqq) { entity = &async_bfqq->entity; if (entity->sched_data != &bfqg->sched_data) { bic_set_bfqq(bic, NULL, 0); bfq_log_bfqq(bfqd, async_bfqq, "bic_change_group: %p %d", async_bfqq, async_bfqq->ref); bfq_put_queue(async_bfqq); } } if (sync_bfqq) { entity = &sync_bfqq->entity; if (entity->sched_data != &bfqg->sched_data) bfq_bfqq_move(bfqd, sync_bfqq, bfqg); } return bfqg; } static void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio) { struct bfq_data *bfqd = bic_to_bfqd(bic); struct bfq_group *bfqg = NULL; uint64_t serial_nr; rcu_read_lock(); serial_nr = bio_blkcg(bio)->css.serial_nr; /* * Check whether blkcg has changed. The condition may trigger * spuriously on a newly created cic but there's no harm. */ if (unlikely(!bfqd) || likely(bic->blkcg_serial_nr == serial_nr)) goto out; bfqg = __bfq_bic_change_cgroup(bfqd, bic, bio_blkcg(bio)); bic->blkcg_serial_nr = serial_nr; out: rcu_read_unlock(); } /** * bfq_flush_idle_tree - deactivate any entity on the idle tree of @st. * @st: the service tree being flushed. */ static void bfq_flush_idle_tree(struct bfq_service_tree *st) { struct bfq_entity *entity = st->first_idle; for (; entity ; entity = st->first_idle) __bfq_deactivate_entity(entity, false); } /** * bfq_reparent_leaf_entity - move leaf entity to the root_group. * @bfqd: the device data structure with the root group. * @entity: the entity to move. */ static void bfq_reparent_leaf_entity(struct bfq_data *bfqd, struct bfq_entity *entity) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); bfq_bfqq_move(bfqd, bfqq, bfqd->root_group); } /** * bfq_reparent_active_entities - move to the root group all active * entities. * @bfqd: the device data structure with the root group. * @bfqg: the group to move from. * @st: the service tree with the entities. * * Needs queue_lock to be taken and reference to be valid over the call. */ static void bfq_reparent_active_entities(struct bfq_data *bfqd, struct bfq_group *bfqg, struct bfq_service_tree *st) { struct rb_root *active = &st->active; struct bfq_entity *entity = NULL; if (!RB_EMPTY_ROOT(&st->active)) entity = bfq_entity_of(rb_first(active)); for (; entity ; entity = bfq_entity_of(rb_first(active))) bfq_reparent_leaf_entity(bfqd, entity); if (bfqg->sched_data.in_service_entity) bfq_reparent_leaf_entity(bfqd, bfqg->sched_data.in_service_entity); } /** * bfq_pd_offline - deactivate the entity associated with @pd, * and reparent its children entities. * @pd: descriptor of the policy going offline. * * blkio already grabs the queue_lock for us, so no need to use * RCU-based magic */ static void bfq_pd_offline(struct blkg_policy_data *pd) { struct bfq_service_tree *st; struct bfq_group *bfqg = pd_to_bfqg(pd); struct bfq_data *bfqd = bfqg->bfqd; struct bfq_entity *entity = bfqg->my_entity; unsigned long flags; int i; if (!entity) /* root group */ return; spin_lock_irqsave(&bfqd->lock, flags); /* * Empty all service_trees belonging to this group before * deactivating the group itself. */ for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) { st = bfqg->sched_data.service_tree + i; /* * The idle tree may still contain bfq_queues belonging * to exited task because they never migrated to a different * cgroup from the one being destroyed now. No one else * can access them so it's safe to act without any lock. */ bfq_flush_idle_tree(st); /* * It may happen that some queues are still active * (busy) upon group destruction (if the corresponding * processes have been forced to terminate). We move * all the leaf entities corresponding to these queues * to the root_group. * Also, it may happen that the group has an entity * in service, which is disconnected from the active * tree: it must be moved, too. * There is no need to put the sync queues, as the * scheduler has taken no reference. */ bfq_reparent_active_entities(bfqd, bfqg, st); } __bfq_deactivate_entity(entity, false); bfq_put_async_queues(bfqd, bfqg); bfq_unlock_put_ioc_restore(bfqd, flags); /* * @blkg is going offline and will be ignored by * blkg_[rw]stat_recursive_sum(). Transfer stats to the parent so * that they don't get lost. If IOs complete after this point, the * stats for them will be lost. Oh well... */ bfqg_stats_xfer_dead(bfqg); } static void bfq_end_wr_async(struct bfq_data *bfqd) { struct blkcg_gq *blkg; list_for_each_entry(blkg, &bfqd->queue->blkg_list, q_node) { struct bfq_group *bfqg = blkg_to_bfqg(blkg); bfq_end_wr_async_queues(bfqd, bfqg); } bfq_end_wr_async_queues(bfqd, bfqd->root_group); } static int bfq_io_show_weight(struct seq_file *sf, void *v) { struct blkcg *blkcg = css_to_blkcg(seq_css(sf)); struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg); unsigned int val = 0; if (bfqgd) val = bfqgd->weight; seq_printf(sf, "%u\n", val); return 0; } static int bfq_io_set_weight_legacy(struct cgroup_subsys_state *css, struct cftype *cftype, u64 val) { struct blkcg *blkcg = css_to_blkcg(css); struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg); struct blkcg_gq *blkg; int ret = -ERANGE; if (val < BFQ_MIN_WEIGHT || val > BFQ_MAX_WEIGHT) return ret; ret = 0; spin_lock_irq(&blkcg->lock); bfqgd->weight = (unsigned short)val; hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) { struct bfq_group *bfqg = blkg_to_bfqg(blkg); if (!bfqg) continue; /* * Setting the prio_changed flag of the entity * to 1 with new_weight == weight would re-set * the value of the weight to its ioprio mapping. * Set the flag only if necessary. */ if ((unsigned short)val != bfqg->entity.new_weight) { bfqg->entity.new_weight = (unsigned short)val; /* * Make sure that the above new value has been * stored in bfqg->entity.new_weight before * setting the prio_changed flag. In fact, * this flag may be read asynchronously (in * critical sections protected by a different * lock than that held here), and finding this * flag set may cause the execution of the code * for updating parameters whose value may * depend also on bfqg->entity.new_weight (in * __bfq_entity_update_weight_prio). * This barrier makes sure that the new value * of bfqg->entity.new_weight is correctly * seen in that code. */ smp_wmb(); bfqg->entity.prio_changed = 1; } } spin_unlock_irq(&blkcg->lock); return ret; } static ssize_t bfq_io_set_weight(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { u64 weight; /* First unsigned long found in the file is used */ int ret = kstrtoull(strim(buf), 0, &weight); if (ret) return ret; return bfq_io_set_weight_legacy(of_css(of), NULL, weight); } static int bfqg_print_stat(struct seq_file *sf, void *v) { blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_stat, &blkcg_policy_bfq, seq_cft(sf)->private, false); return 0; } static int bfqg_print_rwstat(struct seq_file *sf, void *v) { blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_rwstat, &blkcg_policy_bfq, seq_cft(sf)->private, true); return 0; } static u64 bfqg_prfill_stat_recursive(struct seq_file *sf, struct blkg_policy_data *pd, int off) { u64 sum = blkg_stat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_bfq, off); return __blkg_prfill_u64(sf, pd, sum); } static u64 bfqg_prfill_rwstat_recursive(struct seq_file *sf, struct blkg_policy_data *pd, int off) { struct blkg_rwstat sum = blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_bfq, off); return __blkg_prfill_rwstat(sf, pd, &sum); } static int bfqg_print_stat_recursive(struct seq_file *sf, void *v) { blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), bfqg_prfill_stat_recursive, &blkcg_policy_bfq, seq_cft(sf)->private, false); return 0; } static int bfqg_print_rwstat_recursive(struct seq_file *sf, void *v) { blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), bfqg_prfill_rwstat_recursive, &blkcg_policy_bfq, seq_cft(sf)->private, true); return 0; } static u64 bfqg_prfill_sectors(struct seq_file *sf, struct blkg_policy_data *pd, int off) { u64 sum = blkg_rwstat_total(&pd->blkg->stat_bytes); return __blkg_prfill_u64(sf, pd, sum >> 9); } static int bfqg_print_stat_sectors(struct seq_file *sf, void *v) { blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), bfqg_prfill_sectors, &blkcg_policy_bfq, 0, false); return 0; } static u64 bfqg_prfill_sectors_recursive(struct seq_file *sf, struct blkg_policy_data *pd, int off) { struct blkg_rwstat tmp = blkg_rwstat_recursive_sum(pd->blkg, NULL, offsetof(struct blkcg_gq, stat_bytes)); u64 sum = atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) + atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]); return __blkg_prfill_u64(sf, pd, sum >> 9); } static int bfqg_print_stat_sectors_recursive(struct seq_file *sf, void *v) { blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), bfqg_prfill_sectors_recursive, &blkcg_policy_bfq, 0, false); return 0; } static u64 bfqg_prfill_avg_queue_size(struct seq_file *sf, struct blkg_policy_data *pd, int off) { struct bfq_group *bfqg = pd_to_bfqg(pd); u64 samples = blkg_stat_read(&bfqg->stats.avg_queue_size_samples); u64 v = 0; if (samples) { v = blkg_stat_read(&bfqg->stats.avg_queue_size_sum); v = div64_u64(v, samples); } __blkg_prfill_u64(sf, pd, v); return 0; } /* print avg_queue_size */ static int bfqg_print_avg_queue_size(struct seq_file *sf, void *v) { blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), bfqg_prfill_avg_queue_size, &blkcg_policy_bfq, 0, false); return 0; } static struct bfq_group * bfq_create_group_hierarchy(struct bfq_data *bfqd, int node) { int ret; ret = blkcg_activate_policy(bfqd->queue, &blkcg_policy_bfq); if (ret) return NULL; return blkg_to_bfqg(bfqd->queue->root_blkg); } static struct cftype bfq_blkcg_legacy_files[] = { { .name = "bfq.weight", .flags = CFTYPE_NOT_ON_ROOT, .seq_show = bfq_io_show_weight, .write_u64 = bfq_io_set_weight_legacy, }, /* statistics, covers only the tasks in the bfqg */ { .name = "bfq.time", .private = offsetof(struct bfq_group, stats.time), .seq_show = bfqg_print_stat, }, { .name = "bfq.sectors", .seq_show = bfqg_print_stat_sectors, }, { .name = "bfq.io_service_bytes", .private = (unsigned long)&blkcg_policy_bfq, .seq_show = blkg_print_stat_bytes, }, { .name = "bfq.io_serviced", .private = (unsigned long)&blkcg_policy_bfq, .seq_show = blkg_print_stat_ios, }, { .name = "bfq.io_service_time", .private = offsetof(struct bfq_group, stats.service_time), .seq_show = bfqg_print_rwstat, }, { .name = "bfq.io_wait_time", .private = offsetof(struct bfq_group, stats.wait_time), .seq_show = bfqg_print_rwstat, }, { .name = "bfq.io_merged", .private = offsetof(struct bfq_group, stats.merged), .seq_show = bfqg_print_rwstat, }, { .name = "bfq.io_queued", .private = offsetof(struct bfq_group, stats.queued), .seq_show = bfqg_print_rwstat, }, /* the same statictics which cover the bfqg and its descendants */ { .name = "bfq.time_recursive", .private = offsetof(struct bfq_group, stats.time), .seq_show = bfqg_print_stat_recursive, }, { .name = "bfq.sectors_recursive", .seq_show = bfqg_print_stat_sectors_recursive, }, { .name = "bfq.io_service_bytes_recursive", .private = (unsigned long)&blkcg_policy_bfq, .seq_show = blkg_print_stat_bytes_recursive, }, { .name = "bfq.io_serviced_recursive", .private = (unsigned long)&blkcg_policy_bfq, .seq_show = blkg_print_stat_ios_recursive, }, { .name = "bfq.io_service_time_recursive", .private = offsetof(struct bfq_group, stats.service_time), .seq_show = bfqg_print_rwstat_recursive, }, { .name = "bfq.io_wait_time_recursive", .private = offsetof(struct bfq_group, stats.wait_time), .seq_show = bfqg_print_rwstat_recursive, }, { .name = "bfq.io_merged_recursive", .private = offsetof(struct bfq_group, stats.merged), .seq_show = bfqg_print_rwstat_recursive, }, { .name = "bfq.io_queued_recursive", .private = offsetof(struct bfq_group, stats.queued), .seq_show = bfqg_print_rwstat_recursive, }, { .name = "bfq.avg_queue_size", .seq_show = bfqg_print_avg_queue_size, }, { .name = "bfq.group_wait_time", .private = offsetof(struct bfq_group, stats.group_wait_time), .seq_show = bfqg_print_stat, }, { .name = "bfq.idle_time", .private = offsetof(struct bfq_group, stats.idle_time), .seq_show = bfqg_print_stat, }, { .name = "bfq.empty_time", .private = offsetof(struct bfq_group, stats.empty_time), .seq_show = bfqg_print_stat, }, { .name = "bfq.dequeue", .private = offsetof(struct bfq_group, stats.dequeue), .seq_show = bfqg_print_stat, }, { } /* terminate */ }; static struct cftype bfq_blkg_files[] = { { .name = "bfq.weight", .flags = CFTYPE_NOT_ON_ROOT, .seq_show = bfq_io_show_weight, .write = bfq_io_set_weight, }, {} /* terminate */ }; #else /* CONFIG_BFQ_GROUP_IOSCHED */ static inline void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq, unsigned int op) { } static inline void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op) { } static inline void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op) { } static inline void bfqg_stats_update_completion(struct bfq_group *bfqg, uint64_t start_time, uint64_t io_start_time, unsigned int op) { } static inline void bfqg_stats_set_start_group_wait_time(struct bfq_group *bfqg, struct bfq_group *curr_bfqg) { } static inline void bfqg_stats_end_empty_time(struct bfqg_stats *stats) { } static inline void bfqg_stats_update_dequeue(struct bfq_group *bfqg) { } static inline void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg) { } static inline void bfqg_stats_update_idle_time(struct bfq_group *bfqg) { } static inline void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg) { } static inline void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg) { } static void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct bfq_group *bfqg) {} static void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); entity->weight = entity->new_weight; entity->orig_weight = entity->new_weight; if (bfqq) { bfqq->ioprio = bfqq->new_ioprio; bfqq->ioprio_class = bfqq->new_ioprio_class; } entity->sched_data = &bfqg->sched_data; } static void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio) {} static void bfq_end_wr_async(struct bfq_data *bfqd) { bfq_end_wr_async_queues(bfqd, bfqd->root_group); } static struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd, struct blkcg *blkcg) { return bfqd->root_group; } static struct bfq_group *bfqq_group(struct bfq_queue *bfqq) { return bfqq->bfqd->root_group; } static struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node) { struct bfq_group *bfqg; int i; bfqg = kmalloc_node(sizeof(*bfqg), GFP_KERNEL | __GFP_ZERO, node); if (!bfqg) return NULL; for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) bfqg->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT; return bfqg; } #endif /* CONFIG_BFQ_GROUP_IOSCHED */ #define bfq_class_idle(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_IDLE) #define bfq_class_rt(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_RT) #define bfq_sample_valid(samples) ((samples) > 80) /* * Lifted from AS - choose which of rq1 and rq2 that is best served now. * We choose the request that is closesr to the head right now. Distance * behind the head is penalized and only allowed to a certain extent. */ static struct request *bfq_choose_req(struct bfq_data *bfqd, struct request *rq1, struct request *rq2, sector_t last) { sector_t s1, s2, d1 = 0, d2 = 0; unsigned long back_max; #define BFQ_RQ1_WRAP 0x01 /* request 1 wraps */ #define BFQ_RQ2_WRAP 0x02 /* request 2 wraps */ unsigned int wrap = 0; /* bit mask: requests behind the disk head? */ if (!rq1 || rq1 == rq2) return rq2; if (!rq2) return rq1; if (rq_is_sync(rq1) && !rq_is_sync(rq2)) return rq1; else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) return rq2; if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META)) return rq1; else if ((rq2->cmd_flags & REQ_META) && !(rq1->cmd_flags & REQ_META)) return rq2; s1 = blk_rq_pos(rq1); s2 = blk_rq_pos(rq2); /* * By definition, 1KiB is 2 sectors. */ back_max = bfqd->bfq_back_max * 2; /* * Strict one way elevator _except_ in the case where we allow * short backward seeks which are biased as twice the cost of a * similar forward seek. */ if (s1 >= last) d1 = s1 - last; else if (s1 + back_max >= last) d1 = (last - s1) * bfqd->bfq_back_penalty; else wrap |= BFQ_RQ1_WRAP; if (s2 >= last) d2 = s2 - last; else if (s2 + back_max >= last) d2 = (last - s2) * bfqd->bfq_back_penalty; else wrap |= BFQ_RQ2_WRAP; /* Found required data */ /* * By doing switch() on the bit mask "wrap" we avoid having to * check two variables for all permutations: --> faster! */ switch (wrap) { case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ if (d1 < d2) return rq1; else if (d2 < d1) return rq2; if (s1 >= s2) return rq1; else return rq2; case BFQ_RQ2_WRAP: return rq1; case BFQ_RQ1_WRAP: return rq2; case BFQ_RQ1_WRAP|BFQ_RQ2_WRAP: /* both rqs wrapped */ default: /* * Since both rqs are wrapped, * start with the one that's further behind head * (--> only *one* back seek required), * since back seek takes more time than forward. */ if (s1 <= s2) return rq1; else return rq2; } } static struct bfq_queue * bfq_rq_pos_tree_lookup(struct bfq_data *bfqd, struct rb_root *root, sector_t sector, struct rb_node **ret_parent, struct rb_node ***rb_link) { struct rb_node **p, *parent; struct bfq_queue *bfqq = NULL; parent = NULL; p = &root->rb_node; while (*p) { struct rb_node **n; parent = *p; bfqq = rb_entry(parent, struct bfq_queue, pos_node); /* * Sort strictly based on sector. Smallest to the left, * largest to the right. */ if (sector > blk_rq_pos(bfqq->next_rq)) n = &(*p)->rb_right; else if (sector < blk_rq_pos(bfqq->next_rq)) n = &(*p)->rb_left; else break; p = n; bfqq = NULL; } *ret_parent = parent; if (rb_link) *rb_link = p; bfq_log(bfqd, "rq_pos_tree_lookup %llu: returning %d", (unsigned long long)sector, bfqq ? bfqq->pid : 0); return bfqq; } static void bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq) { struct rb_node **p, *parent; struct bfq_queue *__bfqq; if (bfqq->pos_root) { rb_erase(&bfqq->pos_node, bfqq->pos_root); bfqq->pos_root = NULL; } if (bfq_class_idle(bfqq)) return; if (!bfqq->next_rq) return; bfqq->pos_root = &bfq_bfqq_to_bfqg(bfqq)->rq_pos_tree; __bfqq = bfq_rq_pos_tree_lookup(bfqd, bfqq->pos_root, blk_rq_pos(bfqq->next_rq), &parent, &p); if (!__bfqq) { rb_link_node(&bfqq->pos_node, parent, p); rb_insert_color(&bfqq->pos_node, bfqq->pos_root); } else bfqq->pos_root = NULL; } /* * Return expired entry, or NULL to just start from scratch in rbtree. */ static struct request *bfq_check_fifo(struct bfq_queue *bfqq, struct request *last) { struct request *rq; if (bfq_bfqq_fifo_expire(bfqq)) return NULL; bfq_mark_bfqq_fifo_expire(bfqq); rq = rq_entry_fifo(bfqq->fifo.next); if (rq == last || ktime_get_ns() < rq->fifo_time) return NULL; bfq_log_bfqq(bfqq->bfqd, bfqq, "check_fifo: returned %p", rq); return rq; } static struct request *bfq_find_next_rq(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct request *last) { struct rb_node *rbnext = rb_next(&last->rb_node); struct rb_node *rbprev = rb_prev(&last->rb_node); struct request *next, *prev = NULL; /* Follow expired path, else get first next available. */ next = bfq_check_fifo(bfqq, last); if (next) return next; if (rbprev) prev = rb_entry_rq(rbprev); if (rbnext) next = rb_entry_rq(rbnext); else { rbnext = rb_first(&bfqq->sort_list); if (rbnext && rbnext != &last->rb_node) next = rb_entry_rq(rbnext); } return bfq_choose_req(bfqd, next, prev, blk_rq_pos(last)); } /* see the definition of bfq_async_charge_factor for details */ static unsigned long bfq_serv_to_charge(struct request *rq, struct bfq_queue *bfqq) { if (bfq_bfqq_sync(bfqq) || bfqq->wr_coeff > 1) return blk_rq_sectors(rq); /* * If there are no weight-raised queues, then amplify service * by just the async charge factor; otherwise amplify service * by twice the async charge factor, to further reduce latency * for weight-raised queues. */ if (bfqq->bfqd->wr_busy_queues == 0) return blk_rq_sectors(rq) * bfq_async_charge_factor; return blk_rq_sectors(rq) * 2 * bfq_async_charge_factor; } /** * bfq_updated_next_req - update the queue after a new next_rq selection. * @bfqd: the device data the queue belongs to. * @bfqq: the queue to update. * * If the first request of a queue changes we make sure that the queue * has enough budget to serve at least its first request (if the * request has grown). We do this because if the queue has not enough * budget for its first request, it has to go through two dispatch * rounds to actually get it dispatched. */ static void bfq_updated_next_req(struct bfq_data *bfqd, struct bfq_queue *bfqq) { struct bfq_entity *entity = &bfqq->entity; struct request *next_rq = bfqq->next_rq; unsigned long new_budget; if (!next_rq) return; if (bfqq == bfqd->in_service_queue) /* * In order not to break guarantees, budgets cannot be * changed after an entity has been selected. */ return; new_budget = max_t(unsigned long, bfqq->max_budget, bfq_serv_to_charge(next_rq, bfqq)); if (entity->budget != new_budget) { entity->budget = new_budget; bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu", new_budget); bfq_requeue_bfqq(bfqd, bfqq); } } static void bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_io_cq *bic) { if (bic->saved_idle_window) bfq_mark_bfqq_idle_window(bfqq); else bfq_clear_bfqq_idle_window(bfqq); if (bic->saved_IO_bound) bfq_mark_bfqq_IO_bound(bfqq); else bfq_clear_bfqq_IO_bound(bfqq); bfqq->ttime = bic->saved_ttime; bfqq->wr_coeff = bic->saved_wr_coeff; bfqq->wr_start_at_switch_to_srt = bic->saved_wr_start_at_switch_to_srt; bfqq->last_wr_start_finish = bic->saved_last_wr_start_finish; bfqq->wr_cur_max_time = bic->saved_wr_cur_max_time; if (bfqq->wr_coeff > 1 && time_is_before_jiffies(bfqq->last_wr_start_finish + bfqq->wr_cur_max_time)) { bfq_log_bfqq(bfqq->bfqd, bfqq, "resume state: switching off wr"); bfqq->wr_coeff = 1; } /* make sure weight will be updated, however we got here */ bfqq->entity.prio_changed = 1; } static int bfqq_process_refs(struct bfq_queue *bfqq) { return bfqq->ref - bfqq->allocated - bfqq->entity.on_st; } static int bfq_bfqq_budget_left(struct bfq_queue *bfqq) { struct bfq_entity *entity = &bfqq->entity; return entity->budget - entity->service; } /* * If enough samples have been computed, return the current max budget * stored in bfqd, which is dynamically updated according to the * estimated disk peak rate; otherwise return the default max budget */ static int bfq_max_budget(struct bfq_data *bfqd) { if (bfqd->budgets_assigned < bfq_stats_min_budgets) return bfq_default_max_budget; else return bfqd->bfq_max_budget; } /* * Return min budget, which is a fraction of the current or default * max budget (trying with 1/32) */ static int bfq_min_budget(struct bfq_data *bfqd) { if (bfqd->budgets_assigned < bfq_stats_min_budgets) return bfq_default_max_budget / 32; else return bfqd->bfq_max_budget / 32; } static void bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq, bool compensate, enum bfqq_expiration reason); /* * The next function, invoked after the input queue bfqq switches from * idle to busy, updates the budget of bfqq. The function also tells * whether the in-service queue should be expired, by returning * true. The purpose of expiring the in-service queue is to give bfqq * the chance to possibly preempt the in-service queue, and the reason * for preempting the in-service queue is to achieve one of the two * goals below. * * 1. Guarantee to bfqq its reserved bandwidth even if bfqq has * expired because it has remained idle. In particular, bfqq may have * expired for one of the following two reasons: * * - BFQQE_NO_MORE_REQUESTS bfqq did not enjoy any device idling * and did not make it to issue a new request before its last * request was served; * * - BFQQE_TOO_IDLE bfqq did enjoy device idling, but did not issue * a new request before the expiration of the idling-time. * * Even if bfqq has expired for one of the above reasons, the process * associated with the queue may be however issuing requests greedily, * and thus be sensitive to the bandwidth it receives (bfqq may have * remained idle for other reasons: CPU high load, bfqq not enjoying * idling, I/O throttling somewhere in the path from the process to * the I/O scheduler, ...). But if, after every expiration for one of * the above two reasons, bfqq has to wait for the service of at least * one full budget of another queue before being served again, then * bfqq is likely to get a much lower bandwidth or resource time than * its reserved ones. To address this issue, two countermeasures need * to be taken. * * First, the budget and the timestamps of bfqq need to be updated in * a special way on bfqq reactivation: they need to be updated as if * bfqq did not remain idle and did not expire. In fact, if they are * computed as if bfqq expired and remained idle until reactivation, * then the process associated with bfqq is treated as if, instead of * being greedy, it stopped issuing requests when bfqq remained idle, * and restarts issuing requests only on this reactivation. In other * words, the scheduler does not help the process recover the "service * hole" between bfqq expiration and reactivation. As a consequence, * the process receives a lower bandwidth than its reserved one. In * contrast, to recover this hole, the budget must be updated as if * bfqq was not expired at all before this reactivation, i.e., it must * be set to the value of the remaining budget when bfqq was * expired. Along the same line, timestamps need to be assigned the * value they had the last time bfqq was selected for service, i.e., * before last expiration. Thus timestamps need to be back-shifted * with respect to their normal computation (see [1] for more details * on this tricky aspect). * * Secondly, to allow the process to recover the hole, the in-service * queue must be expired too, to give bfqq the chance to preempt it * immediately. In fact, if bfqq has to wait for a full budget of the * in-service queue to be completed, then it may become impossible to * let the process recover the hole, even if the back-shifted * timestamps of bfqq are lower than those of the in-service queue. If * this happens for most or all of the holes, then the process may not * receive its reserved bandwidth. In this respect, it is worth noting * that, being the service of outstanding requests unpreemptible, a * little fraction of the holes may however be unrecoverable, thereby * causing a little loss of bandwidth. * * The last important point is detecting whether bfqq does need this * bandwidth recovery. In this respect, the next function deems the * process associated with bfqq greedy, and thus allows it to recover * the hole, if: 1) the process is waiting for the arrival of a new * request (which implies that bfqq expired for one of the above two * reasons), and 2) such a request has arrived soon. The first * condition is controlled through the flag non_blocking_wait_rq, * while the second through the flag arrived_in_time. If both * conditions hold, then the function computes the budget in the * above-described special way, and signals that the in-service queue * should be expired. Timestamp back-shifting is done later in * __bfq_activate_entity. * * 2. Reduce latency. Even if timestamps are not backshifted to let * the process associated with bfqq recover a service hole, bfqq may * however happen to have, after being (re)activated, a lower finish * timestamp than the in-service queue. That is, the next budget of * bfqq may have to be completed before the one of the in-service * queue. If this is the case, then preempting the in-service queue * allows this goal to be achieved, apart from the unpreemptible, * outstanding requests mentioned above. * * Unfortunately, regardless of which of the above two goals one wants * to achieve, service trees need first to be updated to know whether * the in-service queue must be preempted. To have service trees * correctly updated, the in-service queue must be expired and * rescheduled, and bfqq must be scheduled too. This is one of the * most costly operations (in future versions, the scheduling * mechanism may be re-designed in such a way to make it possible to * know whether preemption is needed without needing to update service * trees). In addition, queue preemptions almost always cause random * I/O, and thus loss of throughput. Because of these facts, the next * function adopts the following simple scheme to avoid both costly * operations and too frequent preemptions: it requests the expiration * of the in-service queue (unconditionally) only for queues that need * to recover a hole, or that either are weight-raised or deserve to * be weight-raised. */ static bool bfq_bfqq_update_budg_for_activation(struct bfq_data *bfqd, struct bfq_queue *bfqq, bool arrived_in_time, bool wr_or_deserves_wr) { struct bfq_entity *entity = &bfqq->entity; if (bfq_bfqq_non_blocking_wait_rq(bfqq) && arrived_in_time) { /* * We do not clear the flag non_blocking_wait_rq here, as * the latter is used in bfq_activate_bfqq to signal * that timestamps need to be back-shifted (and is * cleared right after). */ /* * In next assignment we rely on that either * entity->service or entity->budget are not updated * on expiration if bfqq is empty (see * __bfq_bfqq_recalc_budget). Thus both quantities * remain unchanged after such an expiration, and the * following statement therefore assigns to * entity->budget the remaining budget on such an * expiration. For clarity, entity->service is not * updated on expiration in any case, and, in normal * operation, is reset only when bfqq is selected for * service (see bfq_get_next_queue). */ entity->budget = min_t(unsigned long, bfq_bfqq_budget_left(bfqq), bfqq->max_budget); return true; } entity->budget = max_t(unsigned long, bfqq->max_budget, bfq_serv_to_charge(bfqq->next_rq, bfqq)); bfq_clear_bfqq_non_blocking_wait_rq(bfqq); return wr_or_deserves_wr; } static unsigned int bfq_wr_duration(struct bfq_data *bfqd) { u64 dur; if (bfqd->bfq_wr_max_time > 0) return bfqd->bfq_wr_max_time; dur = bfqd->RT_prod; do_div(dur, bfqd->peak_rate); /* * Limit duration between 3 and 13 seconds. Tests show that * higher values than 13 seconds often yield the opposite of * the desired result, i.e., worsen responsiveness by letting * non-interactive and non-soft-real-time applications * preserve weight raising for a too long time interval. * * On the other end, lower values than 3 seconds make it * difficult for most interactive tasks to complete their jobs * before weight-raising finishes. */ if (dur > msecs_to_jiffies(13000)) dur = msecs_to_jiffies(13000); else if (dur < msecs_to_jiffies(3000)) dur = msecs_to_jiffies(3000); return dur; } static void bfq_update_bfqq_wr_on_rq_arrival(struct bfq_data *bfqd, struct bfq_queue *bfqq, unsigned int old_wr_coeff, bool wr_or_deserves_wr, bool interactive, bool soft_rt) { if (old_wr_coeff == 1 && wr_or_deserves_wr) { /* start a weight-raising period */ if (interactive) { bfqq->wr_coeff = bfqd->bfq_wr_coeff; bfqq->wr_cur_max_time = bfq_wr_duration(bfqd); } else { bfqq->wr_start_at_switch_to_srt = jiffies; bfqq->wr_coeff = bfqd->bfq_wr_coeff * BFQ_SOFTRT_WEIGHT_FACTOR; bfqq->wr_cur_max_time = bfqd->bfq_wr_rt_max_time; } /* * If needed, further reduce budget to make sure it is * close to bfqq's backlog, so as to reduce the * scheduling-error component due to a too large * budget. Do not care about throughput consequences, * but only about latency. Finally, do not assign a * too small budget either, to avoid increasing * latency by causing too frequent expirations. */ bfqq->entity.budget = min_t(unsigned long, bfqq->entity.budget, 2 * bfq_min_budget(bfqd)); } else if (old_wr_coeff > 1) { if (interactive) { /* update wr coeff and duration */ bfqq->wr_coeff = bfqd->bfq_wr_coeff; bfqq->wr_cur_max_time = bfq_wr_duration(bfqd); } else if (soft_rt) { /* * The application is now or still meeting the * requirements for being deemed soft rt. We * can then correctly and safely (re)charge * the weight-raising duration for the * application with the weight-raising * duration for soft rt applications. * * In particular, doing this recharge now, i.e., * before the weight-raising period for the * application finishes, reduces the probability * of the following negative scenario: * 1) the weight of a soft rt application is * raised at startup (as for any newly * created application), * 2) since the application is not interactive, * at a certain time weight-raising is * stopped for the application, * 3) at that time the application happens to * still have pending requests, and hence * is destined to not have a chance to be * deemed soft rt before these requests are * completed (see the comments to the * function bfq_bfqq_softrt_next_start() * for details on soft rt detection), * 4) these pending requests experience a high * latency because the application is not * weight-raised while they are pending. */ if (bfqq->wr_cur_max_time != bfqd->bfq_wr_rt_max_time) { bfqq->wr_start_at_switch_to_srt = bfqq->last_wr_start_finish; bfqq->wr_cur_max_time = bfqd->bfq_wr_rt_max_time; bfqq->wr_coeff = bfqd->bfq_wr_coeff * BFQ_SOFTRT_WEIGHT_FACTOR; } bfqq->last_wr_start_finish = jiffies; } } } static bool bfq_bfqq_idle_for_long_time(struct bfq_data *bfqd, struct bfq_queue *bfqq) { return bfqq->dispatched == 0 && time_is_before_jiffies( bfqq->budget_timeout + bfqd->bfq_wr_min_idle_time); } static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, struct bfq_queue *bfqq, int old_wr_coeff, struct request *rq, bool *interactive) { bool soft_rt, wr_or_deserves_wr, bfqq_wants_to_preempt, idle_for_long_time = bfq_bfqq_idle_for_long_time(bfqd, bfqq), /* * See the comments on * bfq_bfqq_update_budg_for_activation for * details on the usage of the next variable. */ arrived_in_time = ktime_get_ns() <= bfqq->ttime.last_end_request + bfqd->bfq_slice_idle * 3; bfqg_stats_update_io_add(bfqq_group(RQ_BFQQ(rq)), bfqq, rq->cmd_flags); /* * bfqq deserves to be weight-raised if: * - it is sync, * - it has been idle for enough time or is soft real-time, * - is linked to a bfq_io_cq (it is not shared in any sense). */ soft_rt = bfqd->bfq_wr_max_softrt_rate > 0 && time_is_before_jiffies(bfqq->soft_rt_next_start); *interactive = idle_for_long_time; wr_or_deserves_wr = bfqd->low_latency && (bfqq->wr_coeff > 1 || (bfq_bfqq_sync(bfqq) && bfqq->bic && (*interactive || soft_rt))); /* * Using the last flag, update budget and check whether bfqq * may want to preempt the in-service queue. */ bfqq_wants_to_preempt = bfq_bfqq_update_budg_for_activation(bfqd, bfqq, arrived_in_time, wr_or_deserves_wr); if (!bfq_bfqq_IO_bound(bfqq)) { if (arrived_in_time) { bfqq->requests_within_timer++; if (bfqq->requests_within_timer >= bfqd->bfq_requests_within_timer) bfq_mark_bfqq_IO_bound(bfqq); } else bfqq->requests_within_timer = 0; } if (bfqd->low_latency) { if (unlikely(time_is_after_jiffies(bfqq->split_time))) /* wraparound */ bfqq->split_time = jiffies - bfqd->bfq_wr_min_idle_time - 1; if (time_is_before_jiffies(bfqq->split_time + bfqd->bfq_wr_min_idle_time)) { bfq_update_bfqq_wr_on_rq_arrival(bfqd, bfqq, old_wr_coeff, wr_or_deserves_wr, *interactive, soft_rt); if (old_wr_coeff != bfqq->wr_coeff) bfqq->entity.prio_changed = 1; } } bfqq->last_idle_bklogged = jiffies; bfqq->service_from_backlogged = 0; bfq_clear_bfqq_softrt_update(bfqq); bfq_add_bfqq_busy(bfqd, bfqq); /* * Expire in-service queue only if preemption may be needed * for guarantees. In this respect, the function * next_queue_may_preempt just checks a simple, necessary * condition, and not a sufficient condition based on * timestamps. In fact, for the latter condition to be * evaluated, timestamps would need first to be updated, and * this operation is quite costly (see the comments on the * function bfq_bfqq_update_budg_for_activation). */ if (bfqd->in_service_queue && bfqq_wants_to_preempt && bfqd->in_service_queue->wr_coeff < bfqq->wr_coeff && next_queue_may_preempt(bfqd)) bfq_bfqq_expire(bfqd, bfqd->in_service_queue, false, BFQQE_PREEMPTED); } static void bfq_add_request(struct request *rq) { struct bfq_queue *bfqq = RQ_BFQQ(rq); struct bfq_data *bfqd = bfqq->bfqd; struct request *next_rq, *prev; unsigned int old_wr_coeff = bfqq->wr_coeff; bool interactive = false; bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq)); bfqq->queued[rq_is_sync(rq)]++; bfqd->queued++; elv_rb_add(&bfqq->sort_list, rq); /* * Check if this request is a better next-serve candidate. */ prev = bfqq->next_rq; next_rq = bfq_choose_req(bfqd, bfqq->next_rq, rq, bfqd->last_position); bfqq->next_rq = next_rq; /* * Adjust priority tree position, if next_rq changes. */ if (prev != bfqq->next_rq) bfq_pos_tree_add_move(bfqd, bfqq); if (!bfq_bfqq_busy(bfqq)) /* switching to busy ... */ bfq_bfqq_handle_idle_busy_switch(bfqd, bfqq, old_wr_coeff, rq, &interactive); else { if (bfqd->low_latency && old_wr_coeff == 1 && !rq_is_sync(rq) && time_is_before_jiffies( bfqq->last_wr_start_finish + bfqd->bfq_wr_min_inter_arr_async)) { bfqq->wr_coeff = bfqd->bfq_wr_coeff; bfqq->wr_cur_max_time = bfq_wr_duration(bfqd); bfqd->wr_busy_queues++; bfqq->entity.prio_changed = 1; } if (prev != bfqq->next_rq) bfq_updated_next_req(bfqd, bfqq); } /* * Assign jiffies to last_wr_start_finish in the following * cases: * * . if bfqq is not going to be weight-raised, because, for * non weight-raised queues, last_wr_start_finish stores the * arrival time of the last request; as of now, this piece * of information is used only for deciding whether to * weight-raise async queues * * . if bfqq is not weight-raised, because, if bfqq is now * switching to weight-raised, then last_wr_start_finish * stores the time when weight-raising starts * * . if bfqq is interactive, because, regardless of whether * bfqq is currently weight-raised, the weight-raising * period must start or restart (this case is considered * separately because it is not detected by the above * conditions, if bfqq is already weight-raised) * * last_wr_start_finish has to be updated also if bfqq is soft * real-time, because the weight-raising period is constantly * restarted on idle-to-busy transitions for these queues, but * this is already done in bfq_bfqq_handle_idle_busy_switch if * needed. */ if (bfqd->low_latency && (old_wr_coeff == 1 || bfqq->wr_coeff == 1 || interactive)) bfqq->last_wr_start_finish = jiffies; } static struct request *bfq_find_rq_fmerge(struct bfq_data *bfqd, struct bio *bio, struct request_queue *q) { struct bfq_queue *bfqq = bfqd->bio_bfqq; if (bfqq) return elv_rb_find(&bfqq->sort_list, bio_end_sector(bio)); return NULL; } static sector_t get_sdist(sector_t last_pos, struct request *rq) { if (last_pos) return abs(blk_rq_pos(rq) - last_pos); return 0; } #if 0 /* Still not clear if we can do without next two functions */ static void bfq_activate_request(struct request_queue *q, struct request *rq) { struct bfq_data *bfqd = q->elevator->elevator_data; bfqd->rq_in_driver++; } static void bfq_deactivate_request(struct request_queue *q, struct request *rq) { struct bfq_data *bfqd = q->elevator->elevator_data; bfqd->rq_in_driver--; } #endif static void bfq_remove_request(struct request_queue *q, struct request *rq) { struct bfq_queue *bfqq = RQ_BFQQ(rq); struct bfq_data *bfqd = bfqq->bfqd; const int sync = rq_is_sync(rq); if (bfqq->next_rq == rq) { bfqq->next_rq = bfq_find_next_rq(bfqd, bfqq, rq); bfq_updated_next_req(bfqd, bfqq); } if (rq->queuelist.prev != &rq->queuelist) list_del_init(&rq->queuelist); bfqq->queued[sync]--; bfqd->queued--; elv_rb_del(&bfqq->sort_list, rq); elv_rqhash_del(q, rq); if (q->last_merge == rq) q->last_merge = NULL; if (RB_EMPTY_ROOT(&bfqq->sort_list)) { bfqq->next_rq = NULL; if (bfq_bfqq_busy(bfqq) && bfqq != bfqd->in_service_queue) { bfq_del_bfqq_busy(bfqd, bfqq, false); /* * bfqq emptied. In normal operation, when * bfqq is empty, bfqq->entity.service and * bfqq->entity.budget must contain, * respectively, the service received and the * budget used last time bfqq emptied. These * facts do not hold in this case, as at least * this last removal occurred while bfqq is * not in service. To avoid inconsistencies, * reset both bfqq->entity.service and * bfqq->entity.budget, if bfqq has still a * process that may issue I/O requests to it. */ bfqq->entity.budget = bfqq->entity.service = 0; } /* * Remove queue from request-position tree as it is empty. */ if (bfqq->pos_root) { rb_erase(&bfqq->pos_node, bfqq->pos_root); bfqq->pos_root = NULL; } } if (rq->cmd_flags & REQ_META) bfqq->meta_pending--; bfqg_stats_update_io_remove(bfqq_group(bfqq), rq->cmd_flags); } static bool bfq_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio) { struct request_queue *q = hctx->queue; struct bfq_data *bfqd = q->elevator->elevator_data; struct request *free = NULL; /* * bfq_bic_lookup grabs the queue_lock: invoke it now and * store its return value for later use, to avoid nesting * queue_lock inside the bfqd->lock. We assume that the bic * returned by bfq_bic_lookup does not go away before * bfqd->lock is taken. */ struct bfq_io_cq *bic = bfq_bic_lookup(bfqd, current->io_context, q); bool ret; spin_lock_irq(&bfqd->lock); if (bic) bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf)); else bfqd->bio_bfqq = NULL; bfqd->bio_bic = bic; ret = blk_mq_sched_try_merge(q, bio, &free); if (free) blk_mq_free_request(free); spin_unlock_irq(&bfqd->lock); return ret; } static int bfq_request_merge(struct request_queue *q, struct request **req, struct bio *bio) { struct bfq_data *bfqd = q->elevator->elevator_data; struct request *__rq; __rq = bfq_find_rq_fmerge(bfqd, bio, q); if (__rq && elv_bio_merge_ok(__rq, bio)) { *req = __rq; return ELEVATOR_FRONT_MERGE; } return ELEVATOR_NO_MERGE; } static void bfq_request_merged(struct request_queue *q, struct request *req, enum elv_merge type) { if (type == ELEVATOR_FRONT_MERGE && rb_prev(&req->rb_node) && blk_rq_pos(req) < blk_rq_pos(container_of(rb_prev(&req->rb_node), struct request, rb_node))) { struct bfq_queue *bfqq = RQ_BFQQ(req); struct bfq_data *bfqd = bfqq->bfqd; struct request *prev, *next_rq; /* Reposition request in its sort_list */ elv_rb_del(&bfqq->sort_list, req); elv_rb_add(&bfqq->sort_list, req); /* Choose next request to be served for bfqq */ prev = bfqq->next_rq; next_rq = bfq_choose_req(bfqd, bfqq->next_rq, req, bfqd->last_position); bfqq->next_rq = next_rq; /* * If next_rq changes, update both the queue's budget to * fit the new request and the queue's position in its * rq_pos_tree. */ if (prev != bfqq->next_rq) { bfq_updated_next_req(bfqd, bfqq); bfq_pos_tree_add_move(bfqd, bfqq); } } } static void bfq_requests_merged(struct request_queue *q, struct request *rq, struct request *next) { struct bfq_queue *bfqq = RQ_BFQQ(rq), *next_bfqq = RQ_BFQQ(next); if (!RB_EMPTY_NODE(&rq->rb_node)) goto end; spin_lock_irq(&bfqq->bfqd->lock); /* * If next and rq belong to the same bfq_queue and next is older * than rq, then reposition rq in the fifo (by substituting next * with rq). Otherwise, if next and rq belong to different * bfq_queues, never reposition rq: in fact, we would have to * reposition it with respect to next's position in its own fifo, * which would most certainly be too expensive with respect to * the benefits. */ if (bfqq == next_bfqq && !list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && next->fifo_time < rq->fifo_time) { list_del_init(&rq->queuelist); list_replace_init(&next->queuelist, &rq->queuelist); rq->fifo_time = next->fifo_time; } if (bfqq->next_rq == next) bfqq->next_rq = rq; bfq_remove_request(q, next); spin_unlock_irq(&bfqq->bfqd->lock); end: bfqg_stats_update_io_merged(bfqq_group(bfqq), next->cmd_flags); } /* Must be called with bfqq != NULL */ static void bfq_bfqq_end_wr(struct bfq_queue *bfqq) { if (bfq_bfqq_busy(bfqq)) bfqq->bfqd->wr_busy_queues--; bfqq->wr_coeff = 1; bfqq->wr_cur_max_time = 0; bfqq->last_wr_start_finish = jiffies; /* * Trigger a weight change on the next invocation of * __bfq_entity_update_weight_prio. */ bfqq->entity.prio_changed = 1; } static void bfq_end_wr_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg) { int i, j; for (i = 0; i < 2; i++) for (j = 0; j < IOPRIO_BE_NR; j++) if (bfqg->async_bfqq[i][j]) bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]); if (bfqg->async_idle_bfqq) bfq_bfqq_end_wr(bfqg->async_idle_bfqq); } static void bfq_end_wr(struct bfq_data *bfqd) { struct bfq_queue *bfqq; spin_lock_irq(&bfqd->lock); list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list) bfq_bfqq_end_wr(bfqq); list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list) bfq_bfqq_end_wr(bfqq); bfq_end_wr_async(bfqd); spin_unlock_irq(&bfqd->lock); } static sector_t bfq_io_struct_pos(void *io_struct, bool request) { if (request) return blk_rq_pos(io_struct); else return ((struct bio *)io_struct)->bi_iter.bi_sector; } static int bfq_rq_close_to_sector(void *io_struct, bool request, sector_t sector) { return abs(bfq_io_struct_pos(io_struct, request) - sector) <= BFQQ_CLOSE_THR; } static struct bfq_queue *bfqq_find_close(struct bfq_data *bfqd, struct bfq_queue *bfqq, sector_t sector) { struct rb_root *root = &bfq_bfqq_to_bfqg(bfqq)->rq_pos_tree; struct rb_node *parent, *node; struct bfq_queue *__bfqq; if (RB_EMPTY_ROOT(root)) return NULL; /* * First, if we find a request starting at the end of the last * request, choose it. */ __bfqq = bfq_rq_pos_tree_lookup(bfqd, root, sector, &parent, NULL); if (__bfqq) return __bfqq; /* * If the exact sector wasn't found, the parent of the NULL leaf * will contain the closest sector (rq_pos_tree sorted by * next_request position). */ __bfqq = rb_entry(parent, struct bfq_queue, pos_node); if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector)) return __bfqq; if (blk_rq_pos(__bfqq->next_rq) < sector) node = rb_next(&__bfqq->pos_node); else node = rb_prev(&__bfqq->pos_node); if (!node) return NULL; __bfqq = rb_entry(node, struct bfq_queue, pos_node); if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector)) return __bfqq; return NULL; } static struct bfq_queue *bfq_find_close_cooperator(struct bfq_data *bfqd, struct bfq_queue *cur_bfqq, sector_t sector) { struct bfq_queue *bfqq; /* * We shall notice if some of the queues are cooperating, * e.g., working closely on the same area of the device. In * that case, we can group them together and: 1) don't waste * time idling, and 2) serve the union of their requests in * the best possible order for throughput. */ bfqq = bfqq_find_close(bfqd, cur_bfqq, sector); if (!bfqq || bfqq == cur_bfqq) return NULL; return bfqq; } static struct bfq_queue * bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq) { int process_refs, new_process_refs; struct bfq_queue *__bfqq; /* * If there are no process references on the new_bfqq, then it is * unsafe to follow the ->new_bfqq chain as other bfqq's in the chain * may have dropped their last reference (not just their last process * reference). */ if (!bfqq_process_refs(new_bfqq)) return NULL; /* Avoid a circular list and skip interim queue merges. */ while ((__bfqq = new_bfqq->new_bfqq)) { if (__bfqq == bfqq) return NULL; new_bfqq = __bfqq; } process_refs = bfqq_process_refs(bfqq); new_process_refs = bfqq_process_refs(new_bfqq); /* * If the process for the bfqq has gone away, there is no * sense in merging the queues. */ if (process_refs == 0 || new_process_refs == 0) return NULL; bfq_log_bfqq(bfqq->bfqd, bfqq, "scheduling merge with queue %d", new_bfqq->pid); /* * Merging is just a redirection: the requests of the process * owning one of the two queues are redirected to the other queue. * The latter queue, in its turn, is set as shared if this is the * first time that the requests of some process are redirected to * it. * * We redirect bfqq to new_bfqq and not the opposite, because we * are in the context of the process owning bfqq, hence we have * the io_cq of this process. So we can immediately configure this * io_cq to redirect the requests of the process to new_bfqq. * * NOTE, even if new_bfqq coincides with the in-service queue, the * io_cq of new_bfqq is not available, because, if the in-service * queue is shared, bfqd->in_service_bic may not point to the * io_cq of the in-service queue. * Redirecting the requests of the process owning bfqq to the * currently in-service queue is in any case the best option, as * we feed the in-service queue with new requests close to the * last request served and, by doing so, hopefully increase the * throughput. */ bfqq->new_bfqq = new_bfqq; new_bfqq->ref += process_refs; return new_bfqq; } static bool bfq_may_be_close_cooperator(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq) { if (bfq_class_idle(bfqq) || bfq_class_idle(new_bfqq) || (bfqq->ioprio_class != new_bfqq->ioprio_class)) return false; /* * If either of the queues has already been detected as seeky, * then merging it with the other queue is unlikely to lead to * sequential I/O. */ if (BFQQ_SEEKY(bfqq) || BFQQ_SEEKY(new_bfqq)) return false; /* * Interleaved I/O is known to be done by (some) applications * only for reads, so it does not make sense to merge async * queues. */ if (!bfq_bfqq_sync(bfqq) || !bfq_bfqq_sync(new_bfqq)) return false; return true; } /* * If this function returns true, then bfqq cannot be merged. The idea * is that true cooperation happens very early after processes start * to do I/O. Usually, late cooperations are just accidental false * positives. In case bfqq is weight-raised, such false positives * would evidently degrade latency guarantees for bfqq. */ static bool wr_from_too_long(struct bfq_queue *bfqq) { return bfqq->wr_coeff > 1 && time_is_before_jiffies(bfqq->last_wr_start_finish + msecs_to_jiffies(100)); } /* * Attempt to schedule a merge of bfqq with the currently in-service * queue or with a close queue among the scheduled queues. Return * NULL if no merge was scheduled, a pointer to the shared bfq_queue * structure otherwise. * * The OOM queue is not allowed to participate to cooperation: in fact, since * the requests temporarily redirected to the OOM queue could be redirected * again to dedicated queues at any time, the state needed to correctly * handle merging with the OOM queue would be quite complex and expensive * to maintain. Besides, in such a critical condition as an out of memory, * the benefits of queue merging may be little relevant, or even negligible. * * Weight-raised queues can be merged only if their weight-raising * period has just started. In fact cooperating processes are usually * started together. Thus, with this filter we avoid false positives * that would jeopardize low-latency guarantees. * * WARNING: queue merging may impair fairness among non-weight raised * queues, for at least two reasons: 1) the original weight of a * merged queue may change during the merged state, 2) even being the * weight the same, a merged queue may be bloated with many more * requests than the ones produced by its originally-associated * process. */ static struct bfq_queue * bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, void *io_struct, bool request) { struct bfq_queue *in_service_bfqq, *new_bfqq; if (bfqq->new_bfqq) return bfqq->new_bfqq; if (!io_struct || wr_from_too_long(bfqq) || unlikely(bfqq == &bfqd->oom_bfqq)) return NULL; /* If there is only one backlogged queue, don't search. */ if (bfqd->busy_queues == 1) return NULL; in_service_bfqq = bfqd->in_service_queue; if (!in_service_bfqq || in_service_bfqq == bfqq || !bfqd->in_service_bic || wr_from_too_long(in_service_bfqq) || unlikely(in_service_bfqq == &bfqd->oom_bfqq)) goto check_scheduled; if (bfq_rq_close_to_sector(io_struct, request, bfqd->last_position) && bfqq->entity.parent == in_service_bfqq->entity.parent && bfq_may_be_close_cooperator(bfqq, in_service_bfqq)) { new_bfqq = bfq_setup_merge(bfqq, in_service_bfqq); if (new_bfqq) return new_bfqq; } /* * Check whether there is a cooperator among currently scheduled * queues. The only thing we need is that the bio/request is not * NULL, as we need it to establish whether a cooperator exists. */ check_scheduled: new_bfqq = bfq_find_close_cooperator(bfqd, bfqq, bfq_io_struct_pos(io_struct, request)); if (new_bfqq && !wr_from_too_long(new_bfqq) && likely(new_bfqq != &bfqd->oom_bfqq) && bfq_may_be_close_cooperator(bfqq, new_bfqq)) return bfq_setup_merge(bfqq, new_bfqq); return NULL; } static void bfq_bfqq_save_state(struct bfq_queue *bfqq) { struct bfq_io_cq *bic = bfqq->bic; /* * If !bfqq->bic, the queue is already shared or its requests * have already been redirected to a shared queue; both idle window * and weight raising state have already been saved. Do nothing. */ if (!bic) return; bic->saved_ttime = bfqq->ttime; bic->saved_idle_window = bfq_bfqq_idle_window(bfqq); bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq); bic->saved_wr_coeff = bfqq->wr_coeff; bic->saved_wr_start_at_switch_to_srt = bfqq->wr_start_at_switch_to_srt; bic->saved_last_wr_start_finish = bfqq->last_wr_start_finish; bic->saved_wr_cur_max_time = bfqq->wr_cur_max_time; } static void bfq_get_bic_reference(struct bfq_queue *bfqq) { /* * If bfqq->bic has a non-NULL value, the bic to which it belongs * is about to begin using a shared bfq_queue. */ if (bfqq->bic) atomic_long_inc(&bfqq->bic->icq.ioc->refcount); } static void bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic, struct bfq_queue *bfqq, struct bfq_queue *new_bfqq) { bfq_log_bfqq(bfqd, bfqq, "merging with queue %lu", (unsigned long)new_bfqq->pid); /* Save weight raising and idle window of the merged queues */ bfq_bfqq_save_state(bfqq); bfq_bfqq_save_state(new_bfqq); if (bfq_bfqq_IO_bound(bfqq)) bfq_mark_bfqq_IO_bound(new_bfqq); bfq_clear_bfqq_IO_bound(bfqq); /* * If bfqq is weight-raised, then let new_bfqq inherit * weight-raising. To reduce false positives, neglect the case * where bfqq has just been created, but has not yet made it * to be weight-raised (which may happen because EQM may merge * bfqq even before bfq_add_request is executed for the first * time for bfqq). */ if (new_bfqq->wr_coeff == 1 && bfqq->wr_coeff > 1) { new_bfqq->wr_coeff = bfqq->wr_coeff; new_bfqq->wr_cur_max_time = bfqq->wr_cur_max_time; new_bfqq->last_wr_start_finish = bfqq->last_wr_start_finish; new_bfqq->wr_start_at_switch_to_srt = bfqq->wr_start_at_switch_to_srt; if (bfq_bfqq_busy(new_bfqq)) bfqd->wr_busy_queues++; new_bfqq->entity.prio_changed = 1; } if (bfqq->wr_coeff > 1) { /* bfqq has given its wr to new_bfqq */ bfqq->wr_coeff = 1; bfqq->entity.prio_changed = 1; if (bfq_bfqq_busy(bfqq)) bfqd->wr_busy_queues--; } bfq_log_bfqq(bfqd, new_bfqq, "merge_bfqqs: wr_busy %d", bfqd->wr_busy_queues); /* * Grab a reference to the bic, to prevent it from being destroyed * before being possibly touched by a bfq_split_bfqq(). */ bfq_get_bic_reference(bfqq); bfq_get_bic_reference(new_bfqq); /* * Merge queues (that is, let bic redirect its requests to new_bfqq) */ bic_set_bfqq(bic, new_bfqq, 1); bfq_mark_bfqq_coop(new_bfqq); /* * new_bfqq now belongs to at least two bics (it is a shared queue): * set new_bfqq->bic to NULL. bfqq either: * - does not belong to any bic any more, and hence bfqq->bic must * be set to NULL, or * - is a queue whose owning bics have already been redirected to a * different queue, hence the queue is destined to not belong to * any bic soon and bfqq->bic is already NULL (therefore the next * assignment causes no harm). */ new_bfqq->bic = NULL; bfqq->bic = NULL; /* release process reference to bfqq */ bfq_put_queue(bfqq); } static bool bfq_allow_bio_merge(struct request_queue *q, struct request *rq, struct bio *bio) { struct bfq_data *bfqd = q->elevator->elevator_data; bool is_sync = op_is_sync(bio->bi_opf); struct bfq_queue *bfqq = bfqd->bio_bfqq, *new_bfqq; /* * Disallow merge of a sync bio into an async request. */ if (is_sync && !rq_is_sync(rq)) return false; /* * Lookup the bfqq that this bio will be queued with. Allow * merge only if rq is queued there. */ if (!bfqq) return false; /* * We take advantage of this function to perform an early merge * of the queues of possible cooperating processes. */ new_bfqq = bfq_setup_cooperator(bfqd, bfqq, bio, false); if (new_bfqq) { /* * bic still points to bfqq, then it has not yet been * redirected to some other bfq_queue, and a queue * merge beween bfqq and new_bfqq can be safely * fulfillled, i.e., bic can be redirected to new_bfqq * and bfqq can be put. */ bfq_merge_bfqqs(bfqd, bfqd->bio_bic, bfqq, new_bfqq); /* * If we get here, bio will be queued into new_queue, * so use new_bfqq to decide whether bio and rq can be * merged. */ bfqq = new_bfqq; /* * Change also bqfd->bio_bfqq, as * bfqd->bio_bic now points to new_bfqq, and * this function may be invoked again (and then may * use again bqfd->bio_bfqq). */ bfqd->bio_bfqq = bfqq; } return bfqq == RQ_BFQQ(rq); } /* * Set the maximum time for the in-service queue to consume its * budget. This prevents seeky processes from lowering the throughput. * In practice, a time-slice service scheme is used with seeky * processes. */ static void bfq_set_budget_timeout(struct bfq_data *bfqd, struct bfq_queue *bfqq) { unsigned int timeout_coeff; if (bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time) timeout_coeff = 1; else timeout_coeff = bfqq->entity.weight / bfqq->entity.orig_weight; bfqd->last_budget_start = ktime_get(); bfqq->budget_timeout = jiffies + bfqd->bfq_timeout * timeout_coeff; } static void __bfq_set_in_service_queue(struct bfq_data *bfqd, struct bfq_queue *bfqq) { if (bfqq) { bfqg_stats_update_avg_queue_size(bfqq_group(bfqq)); bfq_clear_bfqq_fifo_expire(bfqq); bfqd->budgets_assigned = (bfqd->budgets_assigned * 7 + 256) / 8; if (time_is_before_jiffies(bfqq->last_wr_start_finish) && bfqq->wr_coeff > 1 && bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time && time_is_before_jiffies(bfqq->budget_timeout)) { /* * For soft real-time queues, move the start * of the weight-raising period forward by the * time the queue has not received any * service. Otherwise, a relatively long * service delay is likely to cause the * weight-raising period of the queue to end, * because of the short duration of the * weight-raising period of a soft real-time * queue. It is worth noting that this move * is not so dangerous for the other queues, * because soft real-time queues are not * greedy. * * To not add a further variable, we use the * overloaded field budget_timeout to * determine for how long the queue has not * received service, i.e., how much time has * elapsed since the queue expired. However, * this is a little imprecise, because * budget_timeout is set to jiffies if bfqq * not only expires, but also remains with no * request. */ if (time_after(bfqq->budget_timeout, bfqq->last_wr_start_finish)) bfqq->last_wr_start_finish += jiffies - bfqq->budget_timeout; else bfqq->last_wr_start_finish = jiffies; } bfq_set_budget_timeout(bfqd, bfqq); bfq_log_bfqq(bfqd, bfqq, "set_in_service_queue, cur-budget = %d", bfqq->entity.budget); } bfqd->in_service_queue = bfqq; } /* * Get and set a new queue for service. */ static struct bfq_queue *bfq_set_in_service_queue(struct bfq_data *bfqd) { struct bfq_queue *bfqq = bfq_get_next_queue(bfqd); __bfq_set_in_service_queue(bfqd, bfqq); return bfqq; } static void bfq_arm_slice_timer(struct bfq_data *bfqd) { struct bfq_queue *bfqq = bfqd->in_service_queue; struct bfq_io_cq *bic; u32 sl; /* Processes have exited, don't wait. */ bic = bfqd->in_service_bic; if (!bic || atomic_read(&bic->icq.ioc->active_ref) == 0) return; bfq_mark_bfqq_wait_request(bfqq); /* * We don't want to idle for seeks, but we do want to allow * fair distribution of slice time for a process doing back-to-back * seeks. So allow a little bit of time for him to submit a new rq. */ sl = bfqd->bfq_slice_idle; /* * Unless the queue is being weight-raised, grant only minimum * idle time if the queue is seeky. A long idling is preserved * for a weight-raised queue, because it is needed for * guaranteeing to the queue its reserved share of the * throughput. */ if (BFQQ_SEEKY(bfqq) && bfqq->wr_coeff == 1) sl = min_t(u64, sl, BFQ_MIN_TT); bfqd->last_idling_start = ktime_get(); hrtimer_start(&bfqd->idle_slice_timer, ns_to_ktime(sl), HRTIMER_MODE_REL); bfqg_stats_set_start_idle_time(bfqq_group(bfqq)); } /* * In autotuning mode, max_budget is dynamically recomputed as the * amount of sectors transferred in timeout at the estimated peak * rate. This enables BFQ to utilize a full timeslice with a full * budget, even if the in-service queue is served at peak rate. And * this maximises throughput with sequential workloads. */ static unsigned long bfq_calc_max_budget(struct bfq_data *bfqd) { return (u64)bfqd->peak_rate * USEC_PER_MSEC * jiffies_to_msecs(bfqd->bfq_timeout)>>BFQ_RATE_SHIFT; } /* * Update parameters related to throughput and responsiveness, as a * function of the estimated peak rate. See comments on * bfq_calc_max_budget(), and on T_slow and T_fast arrays. */ static void update_thr_responsiveness_params(struct bfq_data *bfqd) { int dev_type = blk_queue_nonrot(bfqd->queue); if (bfqd->bfq_user_max_budget == 0) bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd); if (bfqd->device_speed == BFQ_BFQD_FAST && bfqd->peak_rate < device_speed_thresh[dev_type]) { bfqd->device_speed = BFQ_BFQD_SLOW; bfqd->RT_prod = R_slow[dev_type] * T_slow[dev_type]; } else if (bfqd->device_speed == BFQ_BFQD_SLOW && bfqd->peak_rate > device_speed_thresh[dev_type]) { bfqd->device_speed = BFQ_BFQD_FAST; bfqd->RT_prod = R_fast[dev_type] * T_fast[dev_type]; } bfq_log(bfqd, "dev_type %s dev_speed_class = %s (%llu sects/sec), thresh %llu setcs/sec", dev_type == 0 ? "ROT" : "NONROT", bfqd->device_speed == BFQ_BFQD_FAST ? "FAST" : "SLOW", bfqd->device_speed == BFQ_BFQD_FAST ? (USEC_PER_SEC*(u64)R_fast[dev_type])>>BFQ_RATE_SHIFT : (USEC_PER_SEC*(u64)R_slow[dev_type])>>BFQ_RATE_SHIFT, (USEC_PER_SEC*(u64)device_speed_thresh[dev_type])>> BFQ_RATE_SHIFT); } static void bfq_reset_rate_computation(struct bfq_data *bfqd, struct request *rq) { if (rq != NULL) { /* new rq dispatch now, reset accordingly */ bfqd->last_dispatch = bfqd->first_dispatch = ktime_get_ns(); bfqd->peak_rate_samples = 1; bfqd->sequential_samples = 0; bfqd->tot_sectors_dispatched = bfqd->last_rq_max_size = blk_rq_sectors(rq); } else /* no new rq dispatched, just reset the number of samples */ bfqd->peak_rate_samples = 0; /* full re-init on next disp. */ bfq_log(bfqd, "reset_rate_computation at end, sample %u/%u tot_sects %llu", bfqd->peak_rate_samples, bfqd->sequential_samples, bfqd->tot_sectors_dispatched); } static void bfq_update_rate_reset(struct bfq_data *bfqd, struct request *rq) { u32 rate, weight, divisor; /* * For the convergence property to hold (see comments on * bfq_update_peak_rate()) and for the assessment to be * reliable, a minimum number of samples must be present, and * a minimum amount of time must have elapsed. If not so, do * not compute new rate. Just reset parameters, to get ready * for a new evaluation attempt. */ if (bfqd->peak_rate_samples < BFQ_RATE_MIN_SAMPLES || bfqd->delta_from_first < BFQ_RATE_MIN_INTERVAL) goto reset_computation; /* * If a new request completion has occurred after last * dispatch, then, to approximate the rate at which requests * have been served by the device, it is more precise to * extend the observation interval to the last completion. */ bfqd->delta_from_first = max_t(u64, bfqd->delta_from_first, bfqd->last_completion - bfqd->first_dispatch); /* * Rate computed in sects/usec, and not sects/nsec, for * precision issues. */ rate = div64_ul(bfqd->tot_sectors_dispatched<delta_from_first, NSEC_PER_USEC)); /* * Peak rate not updated if: * - the percentage of sequential dispatches is below 3/4 of the * total, and rate is below the current estimated peak rate * - rate is unreasonably high (> 20M sectors/sec) */ if ((bfqd->sequential_samples < (3 * bfqd->peak_rate_samples)>>2 && rate <= bfqd->peak_rate) || rate > 20<sequential_samples cannot * become equal to bfqd->peak_rate_samples, which, in its * turn, holds true because bfqd->sequential_samples is not * incremented for the first sample. */ weight = (9 * bfqd->sequential_samples) / bfqd->peak_rate_samples; /* * Second step: further refine the weight as a function of the * duration of the observation interval. */ weight = min_t(u32, 8, div_u64(weight * bfqd->delta_from_first, BFQ_RATE_REF_INTERVAL)); /* * Divisor ranging from 10, for minimum weight, to 2, for * maximum weight. */ divisor = 10 - weight; /* * Finally, update peak rate: * * peak_rate = peak_rate * (divisor-1) / divisor + rate / divisor */ bfqd->peak_rate *= divisor-1; bfqd->peak_rate /= divisor; rate /= divisor; /* smoothing constant alpha = 1/divisor */ bfqd->peak_rate += rate; update_thr_responsiveness_params(bfqd); reset_computation: bfq_reset_rate_computation(bfqd, rq); } /* * Update the read/write peak rate (the main quantity used for * auto-tuning, see update_thr_responsiveness_params()). * * It is not trivial to estimate the peak rate (correctly): because of * the presence of sw and hw queues between the scheduler and the * device components that finally serve I/O requests, it is hard to * say exactly when a given dispatched request is served inside the * device, and for how long. As a consequence, it is hard to know * precisely at what rate a given set of requests is actually served * by the device. * * On the opposite end, the dispatch time of any request is trivially * available, and, from this piece of information, the "dispatch rate" * of requests can be immediately computed. So, the idea in the next * function is to use what is known, namely request dispatch times * (plus, when useful, request completion times), to estimate what is * unknown, namely in-device request service rate. * * The main issue is that, because of the above facts, the rate at * which a certain set of requests is dispatched over a certain time * interval can vary greatly with respect to the rate at which the * same requests are then served. But, since the size of any * intermediate queue is limited, and the service scheme is lossless * (no request is silently dropped), the following obvious convergence * property holds: the number of requests dispatched MUST become * closer and closer to the number of requests completed as the * observation interval grows. This is the key property used in * the next function to estimate the peak service rate as a function * of the observed dispatch rate. The function assumes to be invoked * on every request dispatch. */ static void bfq_update_peak_rate(struct bfq_data *bfqd, struct request *rq) { u64 now_ns = ktime_get_ns(); if (bfqd->peak_rate_samples == 0) { /* first dispatch */ bfq_log(bfqd, "update_peak_rate: goto reset, samples %d", bfqd->peak_rate_samples); bfq_reset_rate_computation(bfqd, rq); goto update_last_values; /* will add one sample */ } /* * Device idle for very long: the observation interval lasting * up to this dispatch cannot be a valid observation interval * for computing a new peak rate (similarly to the late- * completion event in bfq_completed_request()). Go to * update_rate_and_reset to have the following three steps * taken: * - close the observation interval at the last (previous) * request dispatch or completion * - compute rate, if possible, for that observation interval * - start a new observation interval with this dispatch */ if (now_ns - bfqd->last_dispatch > 100*NSEC_PER_MSEC && bfqd->rq_in_driver == 0) goto update_rate_and_reset; /* Update sampling information */ bfqd->peak_rate_samples++; if ((bfqd->rq_in_driver > 0 || now_ns - bfqd->last_completion < BFQ_MIN_TT) && get_sdist(bfqd->last_position, rq) < BFQQ_SEEK_THR) bfqd->sequential_samples++; bfqd->tot_sectors_dispatched += blk_rq_sectors(rq); /* Reset max observed rq size every 32 dispatches */ if (likely(bfqd->peak_rate_samples % 32)) bfqd->last_rq_max_size = max_t(u32, blk_rq_sectors(rq), bfqd->last_rq_max_size); else bfqd->last_rq_max_size = blk_rq_sectors(rq); bfqd->delta_from_first = now_ns - bfqd->first_dispatch; /* Target observation interval not yet reached, go on sampling */ if (bfqd->delta_from_first < BFQ_RATE_REF_INTERVAL) goto update_last_values; update_rate_and_reset: bfq_update_rate_reset(bfqd, rq); update_last_values: bfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq); bfqd->last_dispatch = now_ns; } /* * Remove request from internal lists. */ static void bfq_dispatch_remove(struct request_queue *q, struct request *rq) { struct bfq_queue *bfqq = RQ_BFQQ(rq); /* * For consistency, the next instruction should have been * executed after removing the request from the queue and * dispatching it. We execute instead this instruction before * bfq_remove_request() (and hence introduce a temporary * inconsistency), for efficiency. In fact, should this * dispatch occur for a non in-service bfqq, this anticipated * increment prevents two counters related to bfqq->dispatched * from risking to be, first, uselessly decremented, and then * incremented again when the (new) value of bfqq->dispatched * happens to be taken into account. */ bfqq->dispatched++; bfq_update_peak_rate(q->elevator->elevator_data, rq); bfq_remove_request(q, rq); } static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq) { /* * If this bfqq is shared between multiple processes, check * to make sure that those processes are still issuing I/Os * within the mean seek distance. If not, it may be time to * break the queues apart again. */ if (bfq_bfqq_coop(bfqq) && BFQQ_SEEKY(bfqq)) bfq_mark_bfqq_split_coop(bfqq); if (RB_EMPTY_ROOT(&bfqq->sort_list)) { if (bfqq->dispatched == 0) /* * Overloading budget_timeout field to store * the time at which the queue remains with no * backlog and no outstanding request; used by * the weight-raising mechanism. */ bfqq->budget_timeout = jiffies; bfq_del_bfqq_busy(bfqd, bfqq, true); } else { bfq_requeue_bfqq(bfqd, bfqq); /* * Resort priority tree of potential close cooperators. */ bfq_pos_tree_add_move(bfqd, bfqq); } /* * All in-service entities must have been properly deactivated * or requeued before executing the next function, which * resets all in-service entites as no more in service. */ __bfq_bfqd_reset_in_service(bfqd); } /** * __bfq_bfqq_recalc_budget - try to adapt the budget to the @bfqq behavior. * @bfqd: device data. * @bfqq: queue to update. * @reason: reason for expiration. * * Handle the feedback on @bfqq budget at queue expiration. * See the body for detailed comments. */ static void __bfq_bfqq_recalc_budget(struct bfq_data *bfqd, struct bfq_queue *bfqq, enum bfqq_expiration reason) { struct request *next_rq; int budget, min_budget; min_budget = bfq_min_budget(bfqd); if (bfqq->wr_coeff == 1) budget = bfqq->max_budget; else /* * Use a constant, low budget for weight-raised queues, * to help achieve a low latency. Keep it slightly higher * than the minimum possible budget, to cause a little * bit fewer expirations. */ budget = 2 * min_budget; bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last budg %d, budg left %d", bfqq->entity.budget, bfq_bfqq_budget_left(bfqq)); bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last max_budg %d, min budg %d", budget, bfq_min_budget(bfqd)); bfq_log_bfqq(bfqd, bfqq, "recalc_budg: sync %d, seeky %d", bfq_bfqq_sync(bfqq), BFQQ_SEEKY(bfqd->in_service_queue)); if (bfq_bfqq_sync(bfqq) && bfqq->wr_coeff == 1) { switch (reason) { /* * Caveat: in all the following cases we trade latency * for throughput. */ case BFQQE_TOO_IDLE: /* * This is the only case where we may reduce * the budget: if there is no request of the * process still waiting for completion, then * we assume (tentatively) that the timer has * expired because the batch of requests of * the process could have been served with a * smaller budget. Hence, betting that * process will behave in the same way when it * becomes backlogged again, we reduce its * next budget. As long as we guess right, * this budget cut reduces the latency * experienced by the process. * * However, if there are still outstanding * requests, then the process may have not yet * issued its next request just because it is * still waiting for the completion of some of * the still outstanding ones. So in this * subcase we do not reduce its budget, on the * contrary we increase it to possibly boost * the throughput, as discussed in the * comments to the BUDGET_TIMEOUT case. */ if (bfqq->dispatched > 0) /* still outstanding reqs */ budget = min(budget * 2, bfqd->bfq_max_budget); else { if (budget > 5 * min_budget) budget -= 4 * min_budget; else budget = min_budget; } break; case BFQQE_BUDGET_TIMEOUT: /* * We double the budget here because it gives * the chance to boost the throughput if this * is not a seeky process (and has bumped into * this timeout because of, e.g., ZBR). */ budget = min(budget * 2, bfqd->bfq_max_budget); break; case BFQQE_BUDGET_EXHAUSTED: /* * The process still has backlog, and did not * let either the budget timeout or the disk * idling timeout expire. Hence it is not * seeky, has a short thinktime and may be * happy with a higher budget too. So * definitely increase the budget of this good * candidate to boost the disk throughput. */ budget = min(budget * 4, bfqd->bfq_max_budget); break; case BFQQE_NO_MORE_REQUESTS: /* * For queues that expire for this reason, it * is particularly important to keep the * budget close to the actual service they * need. Doing so reduces the timestamp * misalignment problem described in the * comments in the body of * __bfq_activate_entity. In fact, suppose * that a queue systematically expires for * BFQQE_NO_MORE_REQUESTS and presents a * new request in time to enjoy timestamp * back-shifting. The larger the budget of the * queue is with respect to the service the * queue actually requests in each service * slot, the more times the queue can be * reactivated with the same virtual finish * time. It follows that, even if this finish * time is pushed to the system virtual time * to reduce the consequent timestamp * misalignment, the queue unjustly enjoys for * many re-activations a lower finish time * than all newly activated queues. * * The service needed by bfqq is measured * quite precisely by bfqq->entity.service. * Since bfqq does not enjoy device idling, * bfqq->entity.service is equal to the number * of sectors that the process associated with * bfqq requested to read/write before waiting * for request completions, or blocking for * other reasons. */ budget = max_t(int, bfqq->entity.service, min_budget); break; default: return; } } else if (!bfq_bfqq_sync(bfqq)) { /* * Async queues get always the maximum possible * budget, as for them we do not care about latency * (in addition, their ability to dispatch is limited * by the charging factor). */ budget = bfqd->bfq_max_budget; } bfqq->max_budget = budget; if (bfqd->budgets_assigned >= bfq_stats_min_budgets && !bfqd->bfq_user_max_budget) bfqq->max_budget = min(bfqq->max_budget, bfqd->bfq_max_budget); /* * If there is still backlog, then assign a new budget, making * sure that it is large enough for the next request. Since * the finish time of bfqq must be kept in sync with the * budget, be sure to call __bfq_bfqq_expire() *after* this * update. * * If there is no backlog, then no need to update the budget; * it will be updated on the arrival of a new request. */ next_rq = bfqq->next_rq; if (next_rq) bfqq->entity.budget = max_t(unsigned long, bfqq->max_budget, bfq_serv_to_charge(next_rq, bfqq)); bfq_log_bfqq(bfqd, bfqq, "head sect: %u, new budget %d", next_rq ? blk_rq_sectors(next_rq) : 0, bfqq->entity.budget); } /* * Return true if the process associated with bfqq is "slow". The slow * flag is used, in addition to the budget timeout, to reduce the * amount of service provided to seeky processes, and thus reduce * their chances to lower the throughput. More details in the comments * on the function bfq_bfqq_expire(). * * An important observation is in order: as discussed in the comments * on the function bfq_update_peak_rate(), with devices with internal * queues, it is hard if ever possible to know when and for how long * an I/O request is processed by the device (apart from the trivial * I/O pattern where a new request is dispatched only after the * previous one has been completed). This makes it hard to evaluate * the real rate at which the I/O requests of each bfq_queue are * served. In fact, for an I/O scheduler like BFQ, serving a * bfq_queue means just dispatching its requests during its service * slot (i.e., until the budget of the queue is exhausted, or the * queue remains idle, or, finally, a timeout fires). But, during the * service slot of a bfq_queue, around 100 ms at most, the device may * be even still processing requests of bfq_queues served in previous * service slots. On the opposite end, the requests of the in-service * bfq_queue may be completed after the service slot of the queue * finishes. * * Anyway, unless more sophisticated solutions are used * (where possible), the sum of the sizes of the requests dispatched * during the service slot of a bfq_queue is probably the only * approximation available for the service received by the bfq_queue * during its service slot. And this sum is the quantity used in this * function to evaluate the I/O speed of a process. */ static bool bfq_bfqq_is_slow(struct bfq_data *bfqd, struct bfq_queue *bfqq, bool compensate, enum bfqq_expiration reason, unsigned long *delta_ms) { ktime_t delta_ktime; u32 delta_usecs; bool slow = BFQQ_SEEKY(bfqq); /* if delta too short, use seekyness */ if (!bfq_bfqq_sync(bfqq)) return false; if (compensate) delta_ktime = bfqd->last_idling_start; else delta_ktime = ktime_get(); delta_ktime = ktime_sub(delta_ktime, bfqd->last_budget_start); delta_usecs = ktime_to_us(delta_ktime); /* don't use too short time intervals */ if (delta_usecs < 1000) { if (blk_queue_nonrot(bfqd->queue)) /* * give same worst-case guarantees as idling * for seeky */ *delta_ms = BFQ_MIN_TT / NSEC_PER_MSEC; else /* charge at least one seek */ *delta_ms = bfq_slice_idle / NSEC_PER_MSEC; return slow; } *delta_ms = delta_usecs / USEC_PER_MSEC; /* * Use only long (> 20ms) intervals to filter out excessive * spikes in service rate estimation. */ if (delta_usecs > 20000) { /* * Caveat for rotational devices: processes doing I/O * in the slower disk zones tend to be slow(er) even * if not seeky. In this respect, the estimated peak * rate is likely to be an average over the disk * surface. Accordingly, to not be too harsh with * unlucky processes, a process is deemed slow only if * its rate has been lower than half of the estimated * peak rate. */ slow = bfqq->entity.service < bfqd->bfq_max_budget / 2; } bfq_log_bfqq(bfqd, bfqq, "bfq_bfqq_is_slow: slow %d", slow); return slow; } /* * To be deemed as soft real-time, an application must meet two * requirements. First, the application must not require an average * bandwidth higher than the approximate bandwidth required to playback or * record a compressed high-definition video. * The next function is invoked on the completion of the last request of a * batch, to compute the next-start time instant, soft_rt_next_start, such * that, if the next request of the application does not arrive before * soft_rt_next_start, then the above requirement on the bandwidth is met. * * The second requirement is that the request pattern of the application is * isochronous, i.e., that, after issuing a request or a batch of requests, * the application stops issuing new requests until all its pending requests * have been completed. After that, the application may issue a new batch, * and so on. * For this reason the next function is invoked to compute * soft_rt_next_start only for applications that meet this requirement, * whereas soft_rt_next_start is set to infinity for applications that do * not. * * Unfortunately, even a greedy application may happen to behave in an * isochronous way if the CPU load is high. In fact, the application may * stop issuing requests while the CPUs are busy serving other processes, * then restart, then stop again for a while, and so on. In addition, if * the disk achieves a low enough throughput with the request pattern * issued by the application (e.g., because the request pattern is random * and/or the device is slow), then the application may meet the above * bandwidth requirement too. To prevent such a greedy application to be * deemed as soft real-time, a further rule is used in the computation of * soft_rt_next_start: soft_rt_next_start must be higher than the current * time plus the maximum time for which the arrival of a request is waited * for when a sync queue becomes idle, namely bfqd->bfq_slice_idle. * This filters out greedy applications, as the latter issue instead their * next request as soon as possible after the last one has been completed * (in contrast, when a batch of requests is completed, a soft real-time * application spends some time processing data). * * Unfortunately, the last filter may easily generate false positives if * only bfqd->bfq_slice_idle is used as a reference time interval and one * or both the following cases occur: * 1) HZ is so low that the duration of a jiffy is comparable to or higher * than bfqd->bfq_slice_idle. This happens, e.g., on slow devices with * HZ=100. * 2) jiffies, instead of increasing at a constant rate, may stop increasing * for a while, then suddenly 'jump' by several units to recover the lost * increments. This seems to happen, e.g., inside virtual machines. * To address this issue, we do not use as a reference time interval just * bfqd->bfq_slice_idle, but bfqd->bfq_slice_idle plus a few jiffies. In * particular we add the minimum number of jiffies for which the filter * seems to be quite precise also in embedded systems and KVM/QEMU virtual * machines. */ static unsigned long bfq_bfqq_softrt_next_start(struct bfq_data *bfqd, struct bfq_queue *bfqq) { return max(bfqq->last_idle_bklogged + HZ * bfqq->service_from_backlogged / bfqd->bfq_wr_max_softrt_rate, jiffies + nsecs_to_jiffies(bfqq->bfqd->bfq_slice_idle) + 4); } /* * Return the farthest future time instant according to jiffies * macros. */ static unsigned long bfq_greatest_from_now(void) { return jiffies + MAX_JIFFY_OFFSET; } /* * Return the farthest past time instant according to jiffies * macros. */ static unsigned long bfq_smallest_from_now(void) { return jiffies - MAX_JIFFY_OFFSET; } /** * bfq_bfqq_expire - expire a queue. * @bfqd: device owning the queue. * @bfqq: the queue to expire. * @compensate: if true, compensate for the time spent idling. * @reason: the reason causing the expiration. * * If the process associated with bfqq does slow I/O (e.g., because it * issues random requests), we charge bfqq with the time it has been * in service instead of the service it has received (see * bfq_bfqq_charge_time for details on how this goal is achieved). As * a consequence, bfqq will typically get higher timestamps upon * reactivation, and hence it will be rescheduled as if it had * received more service than what it has actually received. In the * end, bfqq receives less service in proportion to how slowly its * associated process consumes its budgets (and hence how seriously it * tends to lower the throughput). In addition, this time-charging * strategy guarantees time fairness among slow processes. In * contrast, if the process associated with bfqq is not slow, we * charge bfqq exactly with the service it has received. * * Charging time to the first type of queues and the exact service to * the other has the effect of using the WF2Q+ policy to schedule the * former on a timeslice basis, without violating service domain * guarantees among the latter. */ static void bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq, bool compensate, enum bfqq_expiration reason) { bool slow; unsigned long delta = 0; struct bfq_entity *entity = &bfqq->entity; int ref; /* * Check whether the process is slow (see bfq_bfqq_is_slow). */ slow = bfq_bfqq_is_slow(bfqd, bfqq, compensate, reason, &delta); /* * Increase service_from_backlogged before next statement, * because the possible next invocation of * bfq_bfqq_charge_time would likely inflate * entity->service. In contrast, service_from_backlogged must * contain real service, to enable the soft real-time * heuristic to correctly compute the bandwidth consumed by * bfqq. */ bfqq->service_from_backlogged += entity->service; /* * As above explained, charge slow (typically seeky) and * timed-out queues with the time and not the service * received, to favor sequential workloads. * * Processes doing I/O in the slower disk zones will tend to * be slow(er) even if not seeky. Therefore, since the * estimated peak rate is actually an average over the disk * surface, these processes may timeout just for bad luck. To * avoid punishing them, do not charge time to processes that * succeeded in consuming at least 2/3 of their budget. This * allows BFQ to preserve enough elasticity to still perform * bandwidth, and not time, distribution with little unlucky * or quasi-sequential processes. */ if (bfqq->wr_coeff == 1 && (slow || (reason == BFQQE_BUDGET_TIMEOUT && bfq_bfqq_budget_left(bfqq) >= entity->budget / 3))) bfq_bfqq_charge_time(bfqd, bfqq, delta); if (reason == BFQQE_TOO_IDLE && entity->service <= 2 * entity->budget / 10) bfq_clear_bfqq_IO_bound(bfqq); if (bfqd->low_latency && bfqq->wr_coeff == 1) bfqq->last_wr_start_finish = jiffies; if (bfqd->low_latency && bfqd->bfq_wr_max_softrt_rate > 0 && RB_EMPTY_ROOT(&bfqq->sort_list)) { /* * If we get here, and there are no outstanding * requests, then the request pattern is isochronous * (see the comments on the function * bfq_bfqq_softrt_next_start()). Thus we can compute * soft_rt_next_start. If, instead, the queue still * has outstanding requests, then we have to wait for * the completion of all the outstanding requests to * discover whether the request pattern is actually * isochronous. */ if (bfqq->dispatched == 0) bfqq->soft_rt_next_start = bfq_bfqq_softrt_next_start(bfqd, bfqq); else { /* * The application is still waiting for the * completion of one or more requests: * prevent it from possibly being incorrectly * deemed as soft real-time by setting its * soft_rt_next_start to infinity. In fact, * without this assignment, the application * would be incorrectly deemed as soft * real-time if: * 1) it issued a new request before the * completion of all its in-flight * requests, and * 2) at that time, its soft_rt_next_start * happened to be in the past. */ bfqq->soft_rt_next_start = bfq_greatest_from_now(); /* * Schedule an update of soft_rt_next_start to when * the task may be discovered to be isochronous. */ bfq_mark_bfqq_softrt_update(bfqq); } } bfq_log_bfqq(bfqd, bfqq, "expire (%d, slow %d, num_disp %d, idle_win %d)", reason, slow, bfqq->dispatched, bfq_bfqq_idle_window(bfqq)); /* * Increase, decrease or leave budget unchanged according to * reason. */ __bfq_bfqq_recalc_budget(bfqd, bfqq, reason); ref = bfqq->ref; __bfq_bfqq_expire(bfqd, bfqq); /* mark bfqq as waiting a request only if a bic still points to it */ if (ref > 1 && !bfq_bfqq_busy(bfqq) && reason != BFQQE_BUDGET_TIMEOUT && reason != BFQQE_BUDGET_EXHAUSTED) bfq_mark_bfqq_non_blocking_wait_rq(bfqq); } /* * Budget timeout is not implemented through a dedicated timer, but * just checked on request arrivals and completions, as well as on * idle timer expirations. */ static bool bfq_bfqq_budget_timeout(struct bfq_queue *bfqq) { return time_is_before_eq_jiffies(bfqq->budget_timeout); } /* * If we expire a queue that is actively waiting (i.e., with the * device idled) for the arrival of a new request, then we may incur * the timestamp misalignment problem described in the body of the * function __bfq_activate_entity. Hence we return true only if this * condition does not hold, or if the queue is slow enough to deserve * only to be kicked off for preserving a high throughput. */ static bool bfq_may_expire_for_budg_timeout(struct bfq_queue *bfqq) { bfq_log_bfqq(bfqq->bfqd, bfqq, "may_budget_timeout: wait_request %d left %d timeout %d", bfq_bfqq_wait_request(bfqq), bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3, bfq_bfqq_budget_timeout(bfqq)); return (!bfq_bfqq_wait_request(bfqq) || bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3) && bfq_bfqq_budget_timeout(bfqq); } /* * For a queue that becomes empty, device idling is allowed only if * this function returns true for the queue. As a consequence, since * device idling plays a critical role in both throughput boosting and * service guarantees, the return value of this function plays a * critical role in both these aspects as well. * * In a nutshell, this function returns true only if idling is * beneficial for throughput or, even if detrimental for throughput, * idling is however necessary to preserve service guarantees (low * latency, desired throughput distribution, ...). In particular, on * NCQ-capable devices, this function tries to return false, so as to * help keep the drives' internal queues full, whenever this helps the * device boost the throughput without causing any service-guarantee * issue. * * In more detail, the return value of this function is obtained by, * first, computing a number of boolean variables that take into * account throughput and service-guarantee issues, and, then, * combining these variables in a logical expression. Most of the * issues taken into account are not trivial. We discuss these issues * individually while introducing the variables. */ static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq) { struct bfq_data *bfqd = bfqq->bfqd; bool idling_boosts_thr, idling_boosts_thr_without_issues, asymmetric_scenario; if (bfqd->strict_guarantees) return true; /* * The next variable takes into account the cases where idling * boosts the throughput. * * The value of the variable is computed considering that * idling is usually beneficial for the throughput if: * (a) the device is not NCQ-capable, or * (b) regardless of the presence of NCQ, the request pattern * for bfqq is I/O-bound (possible throughput losses * caused by granting idling to seeky queues are mitigated * by the fact that, in all scenarios where boosting * throughput is the best thing to do, i.e., in all * symmetric scenarios, only a minimal idle time is * allowed to seeky queues). */ idling_boosts_thr = !bfqd->hw_tag || bfq_bfqq_IO_bound(bfqq); /* * The value of the next variable, * idling_boosts_thr_without_issues, is equal to that of * idling_boosts_thr, unless a special case holds. In this * special case, described below, idling may cause problems to * weight-raised queues. * * When the request pool is saturated (e.g., in the presence * of write hogs), if the processes associated with * non-weight-raised queues ask for requests at a lower rate, * then processes associated with weight-raised queues have a * higher probability to get a request from the pool * immediately (or at least soon) when they need one. Thus * they have a higher probability to actually get a fraction * of the device throughput proportional to their high * weight. This is especially true with NCQ-capable drives, * which enqueue several requests in advance, and further * reorder internally-queued requests. * * For this reason, we force to false the value of * idling_boosts_thr_without_issues if there are weight-raised * busy queues. In this case, and if bfqq is not weight-raised, * this guarantees that the device is not idled for bfqq (if, * instead, bfqq is weight-raised, then idling will be * guaranteed by another variable, see below). Combined with * the timestamping rules of BFQ (see [1] for details), this * behavior causes bfqq, and hence any sync non-weight-raised * queue, to get a lower number of requests served, and thus * to ask for a lower number of requests from the request * pool, before the busy weight-raised queues get served * again. This often mitigates starvation problems in the * presence of heavy write workloads and NCQ, thereby * guaranteeing a higher application and system responsiveness * in these hostile scenarios. */ idling_boosts_thr_without_issues = idling_boosts_thr && bfqd->wr_busy_queues == 0; /* * There is then a case where idling must be performed not for * throughput concerns, but to preserve service guarantees. To * introduce it, we can note that allowing the drive to * enqueue more than one request at a time, and hence * delegating de facto final scheduling decisions to the * drive's internal scheduler, causes loss of control on the * actual request service order. In particular, the critical * situation is when requests from different processes happens * to be present, at the same time, in the internal queue(s) * of the drive. In such a situation, the drive, by deciding * the service order of the internally-queued requests, does * determine also the actual throughput distribution among * these processes. But the drive typically has no notion or * concern about per-process throughput distribution, and * makes its decisions only on a per-request basis. Therefore, * the service distribution enforced by the drive's internal * scheduler is likely to coincide with the desired * device-throughput distribution only in a completely * symmetric scenario where: (i) each of these processes must * get the same throughput as the others; (ii) all these * processes have the same I/O pattern (either sequential or * random). In fact, in such a scenario, the drive will tend * to treat the requests of each of these processes in about * the same way as the requests of the others, and thus to * provide each of these processes with about the same * throughput (which is exactly the desired throughput * distribution). In contrast, in any asymmetric scenario, * device idling is certainly needed to guarantee that bfqq * receives its assigned fraction of the device throughput * (see [1] for details). * * As for sub-condition (i), actually we check only whether * bfqq is being weight-raised. In fact, if bfqq is not being * weight-raised, we have that: * - if the process associated with bfqq is not I/O-bound, then * it is not either latency- or throughput-critical; therefore * idling is not needed for bfqq; * - if the process asociated with bfqq is I/O-bound, then * idling is already granted with bfqq (see the comments on * idling_boosts_thr). * * We do not check sub-condition (ii) at all, i.e., the next * variable is true if and only if bfqq is being * weight-raised. We do not need to control sub-condition (ii) * for the following reason: * - if bfqq is being weight-raised, then idling is already * guaranteed to bfqq by sub-condition (i); * - if bfqq is not being weight-raised, then idling is * already guaranteed to bfqq (only) if it matters, i.e., if * bfqq is associated to a currently I/O-bound process (see * the above comment on sub-condition (i)). * * As a side note, it is worth considering that the above * device-idling countermeasures may however fail in the * following unlucky scenario: if idling is (correctly) * disabled in a time period during which the symmetry * sub-condition holds, and hence the device is allowed to * enqueue many requests, but at some later point in time some * sub-condition stops to hold, then it may become impossible * to let requests be served in the desired order until all * the requests already queued in the device have been served. */ asymmetric_scenario = bfqq->wr_coeff > 1; /* * We have now all the components we need to compute the return * value of the function, which is true only if both the following * conditions hold: * 1) bfqq is sync, because idling make sense only for sync queues; * 2) idling either boosts the throughput (without issues), or * is necessary to preserve service guarantees. */ return bfq_bfqq_sync(bfqq) && (idling_boosts_thr_without_issues || asymmetric_scenario); } /* * If the in-service queue is empty but the function bfq_bfqq_may_idle * returns true, then: * 1) the queue must remain in service and cannot be expired, and * 2) the device must be idled to wait for the possible arrival of a new * request for the queue. * See the comments on the function bfq_bfqq_may_idle for the reasons * why performing device idling is the best choice to boost the throughput * and preserve service guarantees when bfq_bfqq_may_idle itself * returns true. */ static bool bfq_bfqq_must_idle(struct bfq_queue *bfqq) { struct bfq_data *bfqd = bfqq->bfqd; return RB_EMPTY_ROOT(&bfqq->sort_list) && bfqd->bfq_slice_idle != 0 && bfq_bfqq_may_idle(bfqq); } /* * Select a queue for service. If we have a current queue in service, * check whether to continue servicing it, or retrieve and set a new one. */ static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd) { struct bfq_queue *bfqq; struct request *next_rq; enum bfqq_expiration reason = BFQQE_BUDGET_TIMEOUT; bfqq = bfqd->in_service_queue; if (!bfqq) goto new_queue; bfq_log_bfqq(bfqd, bfqq, "select_queue: already in-service queue"); if (bfq_may_expire_for_budg_timeout(bfqq) && !bfq_bfqq_wait_request(bfqq) && !bfq_bfqq_must_idle(bfqq)) goto expire; check_queue: /* * This loop is rarely executed more than once. Even when it * happens, it is much more convenient to re-execute this loop * than to return NULL and trigger a new dispatch to get a * request served. */ next_rq = bfqq->next_rq; /* * If bfqq has requests queued and it has enough budget left to * serve them, keep the queue, otherwise expire it. */ if (next_rq) { if (bfq_serv_to_charge(next_rq, bfqq) > bfq_bfqq_budget_left(bfqq)) { /* * Expire the queue for budget exhaustion, * which makes sure that the next budget is * enough to serve the next request, even if * it comes from the fifo expired path. */ reason = BFQQE_BUDGET_EXHAUSTED; goto expire; } else { /* * The idle timer may be pending because we may * not disable disk idling even when a new request * arrives. */ if (bfq_bfqq_wait_request(bfqq)) { /* * If we get here: 1) at least a new request * has arrived but we have not disabled the * timer because the request was too small, * 2) then the block layer has unplugged * the device, causing the dispatch to be * invoked. * * Since the device is unplugged, now the * requests are probably large enough to * provide a reasonable throughput. * So we disable idling. */ bfq_clear_bfqq_wait_request(bfqq); hrtimer_try_to_cancel(&bfqd->idle_slice_timer); bfqg_stats_update_idle_time(bfqq_group(bfqq)); } goto keep_queue; } } /* * No requests pending. However, if the in-service queue is idling * for a new request, or has requests waiting for a completion and * may idle after their completion, then keep it anyway. */ if (bfq_bfqq_wait_request(bfqq) || (bfqq->dispatched != 0 && bfq_bfqq_may_idle(bfqq))) { bfqq = NULL; goto keep_queue; } reason = BFQQE_NO_MORE_REQUESTS; expire: bfq_bfqq_expire(bfqd, bfqq, false, reason); new_queue: bfqq = bfq_set_in_service_queue(bfqd); if (bfqq) { bfq_log_bfqq(bfqd, bfqq, "select_queue: checking new queue"); goto check_queue; } keep_queue: if (bfqq) bfq_log_bfqq(bfqd, bfqq, "select_queue: returned this queue"); else bfq_log(bfqd, "select_queue: no queue returned"); return bfqq; } static void bfq_update_wr_data(struct bfq_data *bfqd, struct bfq_queue *bfqq) { struct bfq_entity *entity = &bfqq->entity; if (bfqq->wr_coeff > 1) { /* queue is being weight-raised */ bfq_log_bfqq(bfqd, bfqq, "raising period dur %u/%u msec, old coeff %u, w %d(%d)", jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish), jiffies_to_msecs(bfqq->wr_cur_max_time), bfqq->wr_coeff, bfqq->entity.weight, bfqq->entity.orig_weight); if (entity->prio_changed) bfq_log_bfqq(bfqd, bfqq, "WARN: pending prio change"); /* * If too much time has elapsed from the beginning of * this weight-raising period, then end weight raising. */ if (time_is_before_jiffies(bfqq->last_wr_start_finish + bfqq->wr_cur_max_time)) { if (bfqq->wr_cur_max_time != bfqd->bfq_wr_rt_max_time || time_is_before_jiffies(bfqq->wr_start_at_switch_to_srt + bfq_wr_duration(bfqd))) bfq_bfqq_end_wr(bfqq); else { /* switch back to interactive wr */ bfqq->wr_coeff = bfqd->bfq_wr_coeff; bfqq->wr_cur_max_time = bfq_wr_duration(bfqd); bfqq->last_wr_start_finish = bfqq->wr_start_at_switch_to_srt; bfqq->entity.prio_changed = 1; } } } /* Update weight both if it must be raised and if it must be lowered */ if ((entity->weight > entity->orig_weight) != (bfqq->wr_coeff > 1)) __bfq_entity_update_weight_prio( bfq_entity_service_tree(entity), entity); } /* * Dispatch next request from bfqq. */ static struct request *bfq_dispatch_rq_from_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) { struct request *rq = bfqq->next_rq; unsigned long service_to_charge; service_to_charge = bfq_serv_to_charge(rq, bfqq); bfq_bfqq_served(bfqq, service_to_charge); bfq_dispatch_remove(bfqd->queue, rq); /* * If weight raising has to terminate for bfqq, then next * function causes an immediate update of bfqq's weight, * without waiting for next activation. As a consequence, on * expiration, bfqq will be timestamped as if has never been * weight-raised during this service slot, even if it has * received part or even most of the service as a * weight-raised queue. This inflates bfqq's timestamps, which * is beneficial, as bfqq is then more willing to leave the * device immediately to possible other weight-raised queues. */ bfq_update_wr_data(bfqd, bfqq); if (!bfqd->in_service_bic) { atomic_long_inc(&RQ_BIC(rq)->icq.ioc->refcount); bfqd->in_service_bic = RQ_BIC(rq); } /* * Expire bfqq, pretending that its budget expired, if bfqq * belongs to CLASS_IDLE and other queues are waiting for * service. */ if (bfqd->busy_queues > 1 && bfq_class_idle(bfqq)) goto expire; return rq; expire: bfq_bfqq_expire(bfqd, bfqq, false, BFQQE_BUDGET_EXHAUSTED); return rq; } static bool bfq_has_work(struct blk_mq_hw_ctx *hctx) { struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; /* * Avoiding lock: a race on bfqd->busy_queues should cause at * most a call to dispatch for nothing */ return !list_empty_careful(&bfqd->dispatch) || bfqd->busy_queues > 0; } static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) { struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; struct request *rq = NULL; struct bfq_queue *bfqq = NULL; if (!list_empty(&bfqd->dispatch)) { rq = list_first_entry(&bfqd->dispatch, struct request, queuelist); list_del_init(&rq->queuelist); bfqq = RQ_BFQQ(rq); if (bfqq) { /* * Increment counters here, because this * dispatch does not follow the standard * dispatch flow (where counters are * incremented) */ bfqq->dispatched++; goto inc_in_driver_start_rq; } /* * We exploit the put_rq_private hook to decrement * rq_in_driver, but put_rq_private will not be * invoked on this request. So, to avoid unbalance, * just start this request, without incrementing * rq_in_driver. As a negative consequence, * rq_in_driver is deceptively lower than it should be * while this request is in service. This may cause * bfq_schedule_dispatch to be invoked uselessly. * * As for implementing an exact solution, the * put_request hook, if defined, is probably invoked * also on this request. So, by exploiting this hook, * we could 1) increment rq_in_driver here, and 2) * decrement it in put_request. Such a solution would * let the value of the counter be always accurate, * but it would entail using an extra interface * function. This cost seems higher than the benefit, * being the frequency of non-elevator-private * requests very low. */ goto start_rq; } bfq_log(bfqd, "dispatch requests: %d busy queues", bfqd->busy_queues); if (bfqd->busy_queues == 0) goto exit; /* * Force device to serve one request at a time if * strict_guarantees is true. Forcing this service scheme is * currently the ONLY way to guarantee that the request * service order enforced by the scheduler is respected by a * queueing device. Otherwise the device is free even to make * some unlucky request wait for as long as the device * wishes. * * Of course, serving one request at at time may cause loss of * throughput. */ if (bfqd->strict_guarantees && bfqd->rq_in_driver > 0) goto exit; bfqq = bfq_select_queue(bfqd); if (!bfqq) goto exit; rq = bfq_dispatch_rq_from_bfqq(bfqd, bfqq); if (rq) { inc_in_driver_start_rq: bfqd->rq_in_driver++; start_rq: rq->rq_flags |= RQF_STARTED; } exit: return rq; } static struct request *bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) { struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; struct request *rq; spin_lock_irq(&bfqd->lock); rq = __bfq_dispatch_request(hctx); bfq_unlock_put_ioc(bfqd); return rq; } /* * Task holds one reference to the queue, dropped when task exits. Each rq * in-flight on this queue also holds a reference, dropped when rq is freed. * * Scheduler lock must be held here. Recall not to use bfqq after calling * this function on it. */ static void bfq_put_queue(struct bfq_queue *bfqq) { #ifdef CONFIG_BFQ_GROUP_IOSCHED struct bfq_group *bfqg = bfqq_group(bfqq); #endif if (bfqq->bfqd) bfq_log_bfqq(bfqq->bfqd, bfqq, "put_queue: %p %d", bfqq, bfqq->ref); bfqq->ref--; if (bfqq->ref) return; bfq_log_bfqq(bfqq->bfqd, bfqq, "put_queue: %p freed", bfqq); kmem_cache_free(bfq_pool, bfqq); #ifdef CONFIG_BFQ_GROUP_IOSCHED bfqg_put(bfqg); #endif } static void bfq_put_cooperator(struct bfq_queue *bfqq) { struct bfq_queue *__bfqq, *next; /* * If this queue was scheduled to merge with another queue, be * sure to drop the reference taken on that queue (and others in * the merge chain). See bfq_setup_merge and bfq_merge_bfqqs. */ __bfqq = bfqq->new_bfqq; while (__bfqq) { if (__bfqq == bfqq) break; next = __bfqq->new_bfqq; bfq_put_queue(__bfqq); __bfqq = next; } } static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) { if (bfqq == bfqd->in_service_queue) { __bfq_bfqq_expire(bfqd, bfqq); bfq_schedule_dispatch(bfqd); } bfq_log_bfqq(bfqd, bfqq, "exit_bfqq: %p, %d", bfqq, bfqq->ref); bfq_put_cooperator(bfqq); bfq_put_queue(bfqq); /* release process reference */ } static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync) { struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync); struct bfq_data *bfqd; if (bfqq) bfqd = bfqq->bfqd; /* NULL if scheduler already exited */ if (bfqq && bfqd) { unsigned long flags; spin_lock_irqsave(&bfqd->lock, flags); /* * If the bic is using a shared queue, put the * reference taken on the io_context when the bic * started using a shared bfq_queue. This put cannot * make ioc->ref_count reach 0, then no ioc->lock * risks to be taken (leading to possible deadlock * scenarios). */ if (is_sync && bfq_bfqq_coop(bfqq)) put_io_context(bic->icq.ioc); bfq_exit_bfqq(bfqd, bfqq); bic_set_bfqq(bic, NULL, is_sync); bfq_unlock_put_ioc_restore(bfqd, flags); } } static void bfq_exit_icq(struct io_cq *icq) { struct bfq_io_cq *bic = icq_to_bic(icq); bfq_exit_icq_bfqq(bic, true); bfq_exit_icq_bfqq(bic, false); } /* * Update the entity prio values; note that the new values will not * be used until the next (re)activation. */ static void bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic) { struct task_struct *tsk = current; int ioprio_class; struct bfq_data *bfqd = bfqq->bfqd; if (!bfqd) return; ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio); switch (ioprio_class) { default: dev_err(bfqq->bfqd->queue->backing_dev_info->dev, "bfq: bad prio class %d\n", ioprio_class); case IOPRIO_CLASS_NONE: /* * No prio set, inherit CPU scheduling settings. */ bfqq->new_ioprio = task_nice_ioprio(tsk); bfqq->new_ioprio_class = task_nice_ioclass(tsk); break; case IOPRIO_CLASS_RT: bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio); bfqq->new_ioprio_class = IOPRIO_CLASS_RT; break; case IOPRIO_CLASS_BE: bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio); bfqq->new_ioprio_class = IOPRIO_CLASS_BE; break; case IOPRIO_CLASS_IDLE: bfqq->new_ioprio_class = IOPRIO_CLASS_IDLE; bfqq->new_ioprio = 7; bfq_clear_bfqq_idle_window(bfqq); break; } if (bfqq->new_ioprio >= IOPRIO_BE_NR) { pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n", bfqq->new_ioprio); bfqq->new_ioprio = IOPRIO_BE_NR; } bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio); bfqq->entity.prio_changed = 1; } static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio) { struct bfq_data *bfqd = bic_to_bfqd(bic); struct bfq_queue *bfqq; int ioprio = bic->icq.ioc->ioprio; /* * This condition may trigger on a newly created bic, be sure to * drop the lock before returning. */ if (unlikely(!bfqd) || likely(bic->ioprio == ioprio)) return; bic->ioprio = ioprio; bfqq = bic_to_bfqq(bic, false); if (bfqq) { /* release process reference on this queue */ bfq_put_queue(bfqq); bfqq = bfq_get_queue(bfqd, bio, BLK_RW_ASYNC, bic); bic_set_bfqq(bic, bfqq, false); } bfqq = bic_to_bfqq(bic, true); if (bfqq) bfq_set_next_ioprio_data(bfqq, bic); } static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct bfq_io_cq *bic, pid_t pid, int is_sync) { RB_CLEAR_NODE(&bfqq->entity.rb_node); INIT_LIST_HEAD(&bfqq->fifo); bfqq->ref = 0; bfqq->bfqd = bfqd; if (bic) bfq_set_next_ioprio_data(bfqq, bic); if (is_sync) { if (!bfq_class_idle(bfqq)) bfq_mark_bfqq_idle_window(bfqq); bfq_mark_bfqq_sync(bfqq); } else bfq_clear_bfqq_sync(bfqq); /* set end request to minus infinity from now */ bfqq->ttime.last_end_request = ktime_get_ns() + 1; bfq_mark_bfqq_IO_bound(bfqq); bfqq->pid = pid; /* Tentative initial value to trade off between thr and lat */ bfqq->max_budget = (2 * bfq_max_budget(bfqd)) / 3; bfqq->budget_timeout = bfq_smallest_from_now(); bfqq->wr_coeff = 1; bfqq->last_wr_start_finish = jiffies; bfqq->wr_start_at_switch_to_srt = bfq_smallest_from_now(); bfqq->split_time = bfq_smallest_from_now(); /* * Set to the value for which bfqq will not be deemed as * soft rt when it becomes backlogged. */ bfqq->soft_rt_next_start = bfq_greatest_from_now(); /* first request is almost certainly seeky */ bfqq->seek_history = 1; } static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd, struct bfq_group *bfqg, int ioprio_class, int ioprio) { switch (ioprio_class) { case IOPRIO_CLASS_RT: return &bfqg->async_bfqq[0][ioprio]; case IOPRIO_CLASS_NONE: ioprio = IOPRIO_NORM; /* fall through */ case IOPRIO_CLASS_BE: return &bfqg->async_bfqq[1][ioprio]; case IOPRIO_CLASS_IDLE: return &bfqg->async_idle_bfqq; default: return NULL; } } static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, struct bio *bio, bool is_sync, struct bfq_io_cq *bic) { const int ioprio = IOPRIO_PRIO_DATA(bic->ioprio); const int ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio); struct bfq_queue **async_bfqq = NULL; struct bfq_queue *bfqq; struct bfq_group *bfqg; rcu_read_lock(); bfqg = bfq_find_set_group(bfqd, bio_blkcg(bio)); if (!bfqg) { bfqq = &bfqd->oom_bfqq; goto out; } if (!is_sync) { async_bfqq = bfq_async_queue_prio(bfqd, bfqg, ioprio_class, ioprio); bfqq = *async_bfqq; if (bfqq) goto out; } bfqq = kmem_cache_alloc_node(bfq_pool, GFP_NOWAIT | __GFP_ZERO | __GFP_NOWARN, bfqd->queue->node); if (bfqq) { bfq_init_bfqq(bfqd, bfqq, bic, current->pid, is_sync); bfq_init_entity(&bfqq->entity, bfqg); bfq_log_bfqq(bfqd, bfqq, "allocated"); } else { bfqq = &bfqd->oom_bfqq; bfq_log_bfqq(bfqd, bfqq, "using oom bfqq"); goto out; } /* * Pin the queue now that it's allocated, scheduler exit will * prune it. */ if (async_bfqq) { bfqq->ref++; /* * Extra group reference, w.r.t. sync * queue. This extra reference is removed * only if bfqq->bfqg disappears, to * guarantee that this queue is not freed * until its group goes away. */ bfq_log_bfqq(bfqd, bfqq, "get_queue, bfqq not in async: %p, %d", bfqq, bfqq->ref); *async_bfqq = bfqq; } out: bfqq->ref++; /* get a process reference to this queue */ bfq_log_bfqq(bfqd, bfqq, "get_queue, at end: %p, %d", bfqq, bfqq->ref); rcu_read_unlock(); return bfqq; } static void bfq_update_io_thinktime(struct bfq_data *bfqd, struct bfq_queue *bfqq) { struct bfq_ttime *ttime = &bfqq->ttime; u64 elapsed = ktime_get_ns() - bfqq->ttime.last_end_request; elapsed = min_t(u64, elapsed, 2ULL * bfqd->bfq_slice_idle); ttime->ttime_samples = (7*bfqq->ttime.ttime_samples + 256) / 8; ttime->ttime_total = div_u64(7*ttime->ttime_total + 256*elapsed, 8); ttime->ttime_mean = div64_ul(ttime->ttime_total + 128, ttime->ttime_samples); } static void bfq_update_io_seektime(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct request *rq) { bfqq->seek_history <<= 1; bfqq->seek_history |= get_sdist(bfqq->last_request_pos, rq) > BFQQ_SEEK_THR && (!blk_queue_nonrot(bfqd->queue) || blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT); } /* * Disable idle window if the process thinks too long or seeks so much that * it doesn't matter. */ static void bfq_update_idle_window(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct bfq_io_cq *bic) { int enable_idle; /* Don't idle for async or idle io prio class. */ if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq)) return; /* Idle window just restored, statistics are meaningless. */ if (time_is_after_eq_jiffies(bfqq->split_time + bfqd->bfq_wr_min_idle_time)) return; enable_idle = bfq_bfqq_idle_window(bfqq); if (atomic_read(&bic->icq.ioc->active_ref) == 0 || bfqd->bfq_slice_idle == 0 || (bfqd->hw_tag && BFQQ_SEEKY(bfqq) && bfqq->wr_coeff == 1)) enable_idle = 0; else if (bfq_sample_valid(bfqq->ttime.ttime_samples)) { if (bfqq->ttime.ttime_mean > bfqd->bfq_slice_idle && bfqq->wr_coeff == 1) enable_idle = 0; else enable_idle = 1; } bfq_log_bfqq(bfqd, bfqq, "update_idle_window: enable_idle %d", enable_idle); if (enable_idle) bfq_mark_bfqq_idle_window(bfqq); else bfq_clear_bfqq_idle_window(bfqq); } /* * Called when a new fs request (rq) is added to bfqq. Check if there's * something we should do about it. */ static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct request *rq) { struct bfq_io_cq *bic = RQ_BIC(rq); if (rq->cmd_flags & REQ_META) bfqq->meta_pending++; bfq_update_io_thinktime(bfqd, bfqq); bfq_update_io_seektime(bfqd, bfqq, rq); if (bfqq->entity.service > bfq_max_budget(bfqd) / 8 || !BFQQ_SEEKY(bfqq)) bfq_update_idle_window(bfqd, bfqq, bic); bfq_log_bfqq(bfqd, bfqq, "rq_enqueued: idle_window=%d (seeky %d)", bfq_bfqq_idle_window(bfqq), BFQQ_SEEKY(bfqq)); bfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); if (bfqq == bfqd->in_service_queue && bfq_bfqq_wait_request(bfqq)) { bool small_req = bfqq->queued[rq_is_sync(rq)] == 1 && blk_rq_sectors(rq) < 32; bool budget_timeout = bfq_bfqq_budget_timeout(bfqq); /* * There is just this request queued: if the request * is small and the queue is not to be expired, then * just exit. * * In this way, if the device is being idled to wait * for a new request from the in-service queue, we * avoid unplugging the device and committing the * device to serve just a small request. On the * contrary, we wait for the block layer to decide * when to unplug the device: hopefully, new requests * will be merged to this one quickly, then the device * will be unplugged and larger requests will be * dispatched. */ if (small_req && !budget_timeout) return; /* * A large enough request arrived, or the queue is to * be expired: in both cases disk idling is to be * stopped, so clear wait_request flag and reset * timer. */ bfq_clear_bfqq_wait_request(bfqq); hrtimer_try_to_cancel(&bfqd->idle_slice_timer); bfqg_stats_update_idle_time(bfqq_group(bfqq)); /* * The queue is not empty, because a new request just * arrived. Hence we can safely expire the queue, in * case of budget timeout, without risking that the * timestamps of the queue are not updated correctly. * See [1] for more details. */ if (budget_timeout) bfq_bfqq_expire(bfqd, bfqq, false, BFQQE_BUDGET_TIMEOUT); } } static void __bfq_insert_request(struct bfq_data *bfqd, struct request *rq) { struct bfq_queue *bfqq = RQ_BFQQ(rq), *new_bfqq = bfq_setup_cooperator(bfqd, bfqq, rq, true); if (new_bfqq) { if (bic_to_bfqq(RQ_BIC(rq), 1) != bfqq) new_bfqq = bic_to_bfqq(RQ_BIC(rq), 1); /* * Release the request's reference to the old bfqq * and make sure one is taken to the shared queue. */ new_bfqq->allocated++; bfqq->allocated--; new_bfqq->ref++; /* * If the bic associated with the process * issuing this request still points to bfqq * (and thus has not been already redirected * to new_bfqq or even some other bfq_queue), * then complete the merge and redirect it to * new_bfqq. */ if (bic_to_bfqq(RQ_BIC(rq), 1) == bfqq) bfq_merge_bfqqs(bfqd, RQ_BIC(rq), bfqq, new_bfqq); /* * rq is about to be enqueued into new_bfqq, * release rq reference on bfqq */ bfq_put_queue(bfqq); rq->elv.priv[1] = new_bfqq; bfqq = new_bfqq; } bfq_add_request(rq); rq->fifo_time = ktime_get_ns() + bfqd->bfq_fifo_expire[rq_is_sync(rq)]; list_add_tail(&rq->queuelist, &bfqq->fifo); bfq_rq_enqueued(bfqd, bfqq, rq); } static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, bool at_head) { struct request_queue *q = hctx->queue; struct bfq_data *bfqd = q->elevator->elevator_data; spin_lock_irq(&bfqd->lock); if (blk_mq_sched_try_insert_merge(q, rq)) { spin_unlock_irq(&bfqd->lock); return; } spin_unlock_irq(&bfqd->lock); blk_mq_sched_request_inserted(rq); spin_lock_irq(&bfqd->lock); if (at_head || blk_rq_is_passthrough(rq)) { if (at_head) list_add(&rq->queuelist, &bfqd->dispatch); else list_add_tail(&rq->queuelist, &bfqd->dispatch); } else { __bfq_insert_request(bfqd, rq); if (rq_mergeable(rq)) { elv_rqhash_add(q, rq); if (!q->last_merge) q->last_merge = rq; } } bfq_unlock_put_ioc(bfqd); } static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx, struct list_head *list, bool at_head) { while (!list_empty(list)) { struct request *rq; rq = list_first_entry(list, struct request, queuelist); list_del_init(&rq->queuelist); bfq_insert_request(hctx, rq, at_head); } } static void bfq_update_hw_tag(struct bfq_data *bfqd) { bfqd->max_rq_in_driver = max_t(int, bfqd->max_rq_in_driver, bfqd->rq_in_driver); if (bfqd->hw_tag == 1) return; /* * This sample is valid if the number of outstanding requests * is large enough to allow a queueing behavior. Note that the * sum is not exact, as it's not taking into account deactivated * requests. */ if (bfqd->rq_in_driver + bfqd->queued < BFQ_HW_QUEUE_THRESHOLD) return; if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES) return; bfqd->hw_tag = bfqd->max_rq_in_driver > BFQ_HW_QUEUE_THRESHOLD; bfqd->max_rq_in_driver = 0; bfqd->hw_tag_samples = 0; } static void bfq_completed_request(struct bfq_queue *bfqq, struct bfq_data *bfqd) { u64 now_ns; u32 delta_us; bfq_update_hw_tag(bfqd); bfqd->rq_in_driver--; bfqq->dispatched--; if (!bfqq->dispatched && !bfq_bfqq_busy(bfqq)) { /* * Set budget_timeout (which we overload to store the * time at which the queue remains with no backlog and * no outstanding request; used by the weight-raising * mechanism). */ bfqq->budget_timeout = jiffies; } now_ns = ktime_get_ns(); bfqq->ttime.last_end_request = now_ns; /* * Using us instead of ns, to get a reasonable precision in * computing rate in next check. */ delta_us = div_u64(now_ns - bfqd->last_completion, NSEC_PER_USEC); /* * If the request took rather long to complete, and, according * to the maximum request size recorded, this completion latency * implies that the request was certainly served at a very low * rate (less than 1M sectors/sec), then the whole observation * interval that lasts up to this time instant cannot be a * valid time interval for computing a new peak rate. Invoke * bfq_update_rate_reset to have the following three steps * taken: * - close the observation interval at the last (previous) * request dispatch or completion * - compute rate, if possible, for that observation interval * - reset to zero samples, which will trigger a proper * re-initialization of the observation interval on next * dispatch */ if (delta_us > BFQ_MIN_TT/NSEC_PER_USEC && (bfqd->last_rq_max_size<last_completion = now_ns; /* * If we are waiting to discover whether the request pattern * of the task associated with the queue is actually * isochronous, and both requisites for this condition to hold * are now satisfied, then compute soft_rt_next_start (see the * comments on the function bfq_bfqq_softrt_next_start()). We * schedule this delayed check when bfqq expires, if it still * has in-flight requests. */ if (bfq_bfqq_softrt_update(bfqq) && bfqq->dispatched == 0 && RB_EMPTY_ROOT(&bfqq->sort_list)) bfqq->soft_rt_next_start = bfq_bfqq_softrt_next_start(bfqd, bfqq); /* * If this is the in-service queue, check if it needs to be expired, * or if we want to idle in case it has no pending requests. */ if (bfqd->in_service_queue == bfqq) { if (bfqq->dispatched == 0 && bfq_bfqq_must_idle(bfqq)) { bfq_arm_slice_timer(bfqd); return; } else if (bfq_may_expire_for_budg_timeout(bfqq)) bfq_bfqq_expire(bfqd, bfqq, false, BFQQE_BUDGET_TIMEOUT); else if (RB_EMPTY_ROOT(&bfqq->sort_list) && (bfqq->dispatched == 0 || !bfq_bfqq_may_idle(bfqq))) bfq_bfqq_expire(bfqd, bfqq, false, BFQQE_NO_MORE_REQUESTS); } } static void bfq_put_rq_priv_body(struct bfq_queue *bfqq) { bfqq->allocated--; bfq_put_queue(bfqq); } static void bfq_put_rq_private(struct request_queue *q, struct request *rq) { struct bfq_queue *bfqq = RQ_BFQQ(rq); struct bfq_data *bfqd = bfqq->bfqd; if (rq->rq_flags & RQF_STARTED) bfqg_stats_update_completion(bfqq_group(bfqq), rq_start_time_ns(rq), rq_io_start_time_ns(rq), rq->cmd_flags); if (likely(rq->rq_flags & RQF_STARTED)) { unsigned long flags; spin_lock_irqsave(&bfqd->lock, flags); bfq_completed_request(bfqq, bfqd); bfq_put_rq_priv_body(bfqq); bfq_unlock_put_ioc_restore(bfqd, flags); } else { /* * Request rq may be still/already in the scheduler, * in which case we need to remove it. And we cannot * defer such a check and removal, to avoid * inconsistencies in the time interval from the end * of this function to the start of the deferred work. * This situation seems to occur only in process * context, as a consequence of a merge. In the * current version of the code, this implies that the * lock is held. */ if (!RB_EMPTY_NODE(&rq->rb_node)) bfq_remove_request(q, rq); bfq_put_rq_priv_body(bfqq); } rq->elv.priv[0] = NULL; rq->elv.priv[1] = NULL; } /* * Returns NULL if a new bfqq should be allocated, or the old bfqq if this * was the last process referring to that bfqq. */ static struct bfq_queue * bfq_split_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq) { bfq_log_bfqq(bfqq->bfqd, bfqq, "splitting queue"); if (bfqq_process_refs(bfqq) == 1) { bfqq->pid = current->pid; bfq_clear_bfqq_coop(bfqq); bfq_clear_bfqq_split_coop(bfqq); return bfqq; } bic_set_bfqq(bic, NULL, 1); bfq_put_cooperator(bfqq); bfq_put_queue(bfqq); return NULL; } static struct bfq_queue *bfq_get_bfqq_handle_split(struct bfq_data *bfqd, struct bfq_io_cq *bic, struct bio *bio, bool split, bool is_sync, bool *new_queue) { struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync); if (likely(bfqq && bfqq != &bfqd->oom_bfqq)) return bfqq; if (new_queue) *new_queue = true; if (bfqq) bfq_put_queue(bfqq); bfqq = bfq_get_queue(bfqd, bio, is_sync, bic); bic_set_bfqq(bic, bfqq, is_sync); if (split && is_sync) bfqq->split_time = jiffies; return bfqq; } /* * Allocate bfq data structures associated with this request. */ static int bfq_get_rq_private(struct request_queue *q, struct request *rq, struct bio *bio) { struct bfq_data *bfqd = q->elevator->elevator_data; struct bfq_io_cq *bic = icq_to_bic(rq->elv.icq); const int is_sync = rq_is_sync(rq); struct bfq_queue *bfqq; bool new_queue = false; spin_lock_irq(&bfqd->lock); bfq_check_ioprio_change(bic, bio); if (!bic) goto queue_fail; bfq_bic_update_cgroup(bic, bio); bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio, false, is_sync, &new_queue); if (likely(!new_queue)) { /* If the queue was seeky for too long, break it apart. */ if (bfq_bfqq_coop(bfqq) && bfq_bfqq_split_coop(bfqq)) { bfq_log_bfqq(bfqd, bfqq, "breaking apart bfqq"); bfqq = bfq_split_bfqq(bic, bfqq); /* * A reference to bic->icq.ioc needs to be * released after a queue split. Do not do it * immediately, to not risk to possibly take * an ioc->lock while holding the scheduler * lock. */ bfqd->ioc_to_put = bic->icq.ioc; if (!bfqq) bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio, true, is_sync, NULL); } } bfqq->allocated++; bfqq->ref++; bfq_log_bfqq(bfqd, bfqq, "get_request %p: bfqq %p, %d", rq, bfqq, bfqq->ref); rq->elv.priv[0] = bic; rq->elv.priv[1] = bfqq; /* * If a bfq_queue has only one process reference, it is owned * by only this bic: we can then set bfqq->bic = bic. in * addition, if the queue has also just been split, we have to * resume its state. */ if (likely(bfqq != &bfqd->oom_bfqq) && bfqq_process_refs(bfqq) == 1) { bfqq->bic = bic; if (bfqd->ioc_to_put) { /* if true, there has been a split */ /* * The queue has just been split from a shared * queue: restore the idle window and the * possible weight raising period. */ bfq_bfqq_resume_state(bfqq, bic); } } bfq_unlock_put_ioc(bfqd); return 0; queue_fail: spin_unlock_irq(&bfqd->lock); return 1; } static void bfq_idle_slice_timer_body(struct bfq_queue *bfqq) { struct bfq_data *bfqd = bfqq->bfqd; enum bfqq_expiration reason; unsigned long flags; spin_lock_irqsave(&bfqd->lock, flags); bfq_clear_bfqq_wait_request(bfqq); if (bfqq != bfqd->in_service_queue) { spin_unlock_irqrestore(&bfqd->lock, flags); return; } if (bfq_bfqq_budget_timeout(bfqq)) /* * Also here the queue can be safely expired * for budget timeout without wasting * guarantees */ reason = BFQQE_BUDGET_TIMEOUT; else if (bfqq->queued[0] == 0 && bfqq->queued[1] == 0) /* * The queue may not be empty upon timer expiration, * because we may not disable the timer when the * first request of the in-service queue arrives * during disk idling. */ reason = BFQQE_TOO_IDLE; else goto schedule_dispatch; bfq_bfqq_expire(bfqd, bfqq, true, reason); schedule_dispatch: bfq_unlock_put_ioc_restore(bfqd, flags); bfq_schedule_dispatch(bfqd); } /* * Handler of the expiration of the timer running if the in-service queue * is idling inside its time slice. */ static enum hrtimer_restart bfq_idle_slice_timer(struct hrtimer *timer) { struct bfq_data *bfqd = container_of(timer, struct bfq_data, idle_slice_timer); struct bfq_queue *bfqq = bfqd->in_service_queue; /* * Theoretical race here: the in-service queue can be NULL or * different from the queue that was idling if a new request * arrives for the current queue and there is a full dispatch * cycle that changes the in-service queue. This can hardly * happen, but in the worst case we just expire a queue too * early. */ if (bfqq) bfq_idle_slice_timer_body(bfqq); return HRTIMER_NORESTART; } static void __bfq_put_async_bfqq(struct bfq_data *bfqd, struct bfq_queue **bfqq_ptr) { struct bfq_queue *bfqq = *bfqq_ptr; bfq_log(bfqd, "put_async_bfqq: %p", bfqq); if (bfqq) { bfq_bfqq_move(bfqd, bfqq, bfqd->root_group); bfq_log_bfqq(bfqd, bfqq, "put_async_bfqq: putting %p, %d", bfqq, bfqq->ref); bfq_put_queue(bfqq); *bfqq_ptr = NULL; } } /* * Release all the bfqg references to its async queues. If we are * deallocating the group these queues may still contain requests, so * we reparent them to the root cgroup (i.e., the only one that will * exist for sure until all the requests on a device are gone). */ static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg) { int i, j; for (i = 0; i < 2; i++) for (j = 0; j < IOPRIO_BE_NR; j++) __bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]); __bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq); } static void bfq_exit_queue(struct elevator_queue *e) { struct bfq_data *bfqd = e->elevator_data; struct bfq_queue *bfqq, *n; hrtimer_cancel(&bfqd->idle_slice_timer); spin_lock_irq(&bfqd->lock); list_for_each_entry_safe(bfqq, n, &bfqd->idle_list, bfqq_list) bfq_deactivate_bfqq(bfqd, bfqq, false, false); spin_unlock_irq(&bfqd->lock); hrtimer_cancel(&bfqd->idle_slice_timer); #ifdef CONFIG_BFQ_GROUP_IOSCHED blkcg_deactivate_policy(bfqd->queue, &blkcg_policy_bfq); #else spin_lock_irq(&bfqd->lock); bfq_put_async_queues(bfqd, bfqd->root_group); kfree(bfqd->root_group); spin_unlock_irq(&bfqd->lock); #endif kfree(bfqd); } static void bfq_init_root_group(struct bfq_group *root_group, struct bfq_data *bfqd) { int i; #ifdef CONFIG_BFQ_GROUP_IOSCHED root_group->entity.parent = NULL; root_group->my_entity = NULL; root_group->bfqd = bfqd; #endif root_group->rq_pos_tree = RB_ROOT; for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) root_group->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT; root_group->sched_data.bfq_class_idle_last_service = jiffies; } static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) { struct bfq_data *bfqd; struct elevator_queue *eq; eq = elevator_alloc(q, e); if (!eq) return -ENOMEM; bfqd = kzalloc_node(sizeof(*bfqd), GFP_KERNEL, q->node); if (!bfqd) { kobject_put(&eq->kobj); return -ENOMEM; } eq->elevator_data = bfqd; spin_lock_irq(q->queue_lock); q->elevator = eq; spin_unlock_irq(q->queue_lock); /* * Our fallback bfqq if bfq_find_alloc_queue() runs into OOM issues. * Grab a permanent reference to it, so that the normal code flow * will not attempt to free it. */ bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, NULL, 1, 0); bfqd->oom_bfqq.ref++; bfqd->oom_bfqq.new_ioprio = BFQ_DEFAULT_QUEUE_IOPRIO; bfqd->oom_bfqq.new_ioprio_class = IOPRIO_CLASS_BE; bfqd->oom_bfqq.entity.new_weight = bfq_ioprio_to_weight(bfqd->oom_bfqq.new_ioprio); /* * Trigger weight initialization, according to ioprio, at the * oom_bfqq's first activation. The oom_bfqq's ioprio and ioprio * class won't be changed any more. */ bfqd->oom_bfqq.entity.prio_changed = 1; bfqd->queue = q; INIT_LIST_HEAD(&bfqd->dispatch); hrtimer_init(&bfqd->idle_slice_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); bfqd->idle_slice_timer.function = bfq_idle_slice_timer; INIT_LIST_HEAD(&bfqd->active_list); INIT_LIST_HEAD(&bfqd->idle_list); bfqd->hw_tag = -1; bfqd->bfq_max_budget = bfq_default_max_budget; bfqd->bfq_fifo_expire[0] = bfq_fifo_expire[0]; bfqd->bfq_fifo_expire[1] = bfq_fifo_expire[1]; bfqd->bfq_back_max = bfq_back_max; bfqd->bfq_back_penalty = bfq_back_penalty; bfqd->bfq_slice_idle = bfq_slice_idle; bfqd->bfq_timeout = bfq_timeout; bfqd->bfq_requests_within_timer = 120; bfqd->low_latency = true; /* * Trade-off between responsiveness and fairness. */ bfqd->bfq_wr_coeff = 30; bfqd->bfq_wr_rt_max_time = msecs_to_jiffies(300); bfqd->bfq_wr_max_time = 0; bfqd->bfq_wr_min_idle_time = msecs_to_jiffies(2000); bfqd->bfq_wr_min_inter_arr_async = msecs_to_jiffies(500); bfqd->bfq_wr_max_softrt_rate = 7000; /* * Approximate rate required * to playback or record a * high-definition compressed * video. */ bfqd->wr_busy_queues = 0; /* * Begin by assuming, optimistically, that the device is a * high-speed one, and that its peak rate is equal to 2/3 of * the highest reference rate. */ bfqd->RT_prod = R_fast[blk_queue_nonrot(bfqd->queue)] * T_fast[blk_queue_nonrot(bfqd->queue)]; bfqd->peak_rate = R_fast[blk_queue_nonrot(bfqd->queue)] * 2 / 3; bfqd->device_speed = BFQ_BFQD_FAST; spin_lock_init(&bfqd->lock); /* * The invocation of the next bfq_create_group_hierarchy * function is the head of a chain of function calls * (bfq_create_group_hierarchy->blkcg_activate_policy-> * blk_mq_freeze_queue) that may lead to the invocation of the * has_work hook function. For this reason, * bfq_create_group_hierarchy is invoked only after all * scheduler data has been initialized, apart from the fields * that can be initialized only after invoking * bfq_create_group_hierarchy. This, in particular, enables * has_work to correctly return false. Of course, to avoid * other inconsistencies, the blk-mq stack must then refrain * from invoking further scheduler hooks before this init * function is finished. */ bfqd->root_group = bfq_create_group_hierarchy(bfqd, q->node); if (!bfqd->root_group) goto out_free; bfq_init_root_group(bfqd->root_group, bfqd); bfq_init_entity(&bfqd->oom_bfqq.entity, bfqd->root_group); return 0; out_free: kfree(bfqd); kobject_put(&eq->kobj); return -ENOMEM; } static void bfq_slab_kill(void) { kmem_cache_destroy(bfq_pool); } static int __init bfq_slab_setup(void) { bfq_pool = KMEM_CACHE(bfq_queue, 0); if (!bfq_pool) return -ENOMEM; return 0; } static ssize_t bfq_var_show(unsigned int var, char *page) { return sprintf(page, "%u\n", var); } static ssize_t bfq_var_store(unsigned long *var, const char *page, size_t count) { unsigned long new_val; int ret = kstrtoul(page, 10, &new_val); if (ret == 0) *var = new_val; return count; } #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ static ssize_t __FUNC(struct elevator_queue *e, char *page) \ { \ struct bfq_data *bfqd = e->elevator_data; \ u64 __data = __VAR; \ if (__CONV == 1) \ __data = jiffies_to_msecs(__data); \ else if (__CONV == 2) \ __data = div_u64(__data, NSEC_PER_MSEC); \ return bfq_var_show(__data, (page)); \ } SHOW_FUNCTION(bfq_fifo_expire_sync_show, bfqd->bfq_fifo_expire[1], 2); SHOW_FUNCTION(bfq_fifo_expire_async_show, bfqd->bfq_fifo_expire[0], 2); SHOW_FUNCTION(bfq_back_seek_max_show, bfqd->bfq_back_max, 0); SHOW_FUNCTION(bfq_back_seek_penalty_show, bfqd->bfq_back_penalty, 0); SHOW_FUNCTION(bfq_slice_idle_show, bfqd->bfq_slice_idle, 2); SHOW_FUNCTION(bfq_max_budget_show, bfqd->bfq_user_max_budget, 0); SHOW_FUNCTION(bfq_timeout_sync_show, bfqd->bfq_timeout, 1); SHOW_FUNCTION(bfq_strict_guarantees_show, bfqd->strict_guarantees, 0); SHOW_FUNCTION(bfq_low_latency_show, bfqd->low_latency, 0); #undef SHOW_FUNCTION #define USEC_SHOW_FUNCTION(__FUNC, __VAR) \ static ssize_t __FUNC(struct elevator_queue *e, char *page) \ { \ struct bfq_data *bfqd = e->elevator_data; \ u64 __data = __VAR; \ __data = div_u64(__data, NSEC_PER_USEC); \ return bfq_var_show(__data, (page)); \ } USEC_SHOW_FUNCTION(bfq_slice_idle_us_show, bfqd->bfq_slice_idle); #undef USEC_SHOW_FUNCTION #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ static ssize_t \ __FUNC(struct elevator_queue *e, const char *page, size_t count) \ { \ struct bfq_data *bfqd = e->elevator_data; \ unsigned long uninitialized_var(__data); \ int ret = bfq_var_store(&__data, (page), count); \ if (__data < (MIN)) \ __data = (MIN); \ else if (__data > (MAX)) \ __data = (MAX); \ if (__CONV == 1) \ *(__PTR) = msecs_to_jiffies(__data); \ else if (__CONV == 2) \ *(__PTR) = (u64)__data * NSEC_PER_MSEC; \ else \ *(__PTR) = __data; \ return ret; \ } STORE_FUNCTION(bfq_fifo_expire_sync_store, &bfqd->bfq_fifo_expire[1], 1, INT_MAX, 2); STORE_FUNCTION(bfq_fifo_expire_async_store, &bfqd->bfq_fifo_expire[0], 1, INT_MAX, 2); STORE_FUNCTION(bfq_back_seek_max_store, &bfqd->bfq_back_max, 0, INT_MAX, 0); STORE_FUNCTION(bfq_back_seek_penalty_store, &bfqd->bfq_back_penalty, 1, INT_MAX, 0); STORE_FUNCTION(bfq_slice_idle_store, &bfqd->bfq_slice_idle, 0, INT_MAX, 2); #undef STORE_FUNCTION #define USEC_STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)\ { \ struct bfq_data *bfqd = e->elevator_data; \ unsigned long uninitialized_var(__data); \ int ret = bfq_var_store(&__data, (page), count); \ if (__data < (MIN)) \ __data = (MIN); \ else if (__data > (MAX)) \ __data = (MAX); \ *(__PTR) = (u64)__data * NSEC_PER_USEC; \ return ret; \ } USEC_STORE_FUNCTION(bfq_slice_idle_us_store, &bfqd->bfq_slice_idle, 0, UINT_MAX); #undef USEC_STORE_FUNCTION static ssize_t bfq_max_budget_store(struct elevator_queue *e, const char *page, size_t count) { struct bfq_data *bfqd = e->elevator_data; unsigned long uninitialized_var(__data); int ret = bfq_var_store(&__data, (page), count); if (__data == 0) bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd); else { if (__data > INT_MAX) __data = INT_MAX; bfqd->bfq_max_budget = __data; } bfqd->bfq_user_max_budget = __data; return ret; } /* * Leaving this name to preserve name compatibility with cfq * parameters, but this timeout is used for both sync and async. */ static ssize_t bfq_timeout_sync_store(struct elevator_queue *e, const char *page, size_t count) { struct bfq_data *bfqd = e->elevator_data; unsigned long uninitialized_var(__data); int ret = bfq_var_store(&__data, (page), count); if (__data < 1) __data = 1; else if (__data > INT_MAX) __data = INT_MAX; bfqd->bfq_timeout = msecs_to_jiffies(__data); if (bfqd->bfq_user_max_budget == 0) bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd); return ret; } static ssize_t bfq_strict_guarantees_store(struct elevator_queue *e, const char *page, size_t count) { struct bfq_data *bfqd = e->elevator_data; unsigned long uninitialized_var(__data); int ret = bfq_var_store(&__data, (page), count); if (__data > 1) __data = 1; if (!bfqd->strict_guarantees && __data == 1 && bfqd->bfq_slice_idle < 8 * NSEC_PER_MSEC) bfqd->bfq_slice_idle = 8 * NSEC_PER_MSEC; bfqd->strict_guarantees = __data; return ret; } static ssize_t bfq_low_latency_store(struct elevator_queue *e, const char *page, size_t count) { struct bfq_data *bfqd = e->elevator_data; unsigned long uninitialized_var(__data); int ret = bfq_var_store(&__data, (page), count); if (__data > 1) __data = 1; if (__data == 0 && bfqd->low_latency != 0) bfq_end_wr(bfqd); bfqd->low_latency = __data; return ret; } #define BFQ_ATTR(name) \ __ATTR(name, 0644, bfq_##name##_show, bfq_##name##_store) static struct elv_fs_entry bfq_attrs[] = { BFQ_ATTR(fifo_expire_sync), BFQ_ATTR(fifo_expire_async), BFQ_ATTR(back_seek_max), BFQ_ATTR(back_seek_penalty), BFQ_ATTR(slice_idle), BFQ_ATTR(slice_idle_us), BFQ_ATTR(max_budget), BFQ_ATTR(timeout_sync), BFQ_ATTR(strict_guarantees), BFQ_ATTR(low_latency), __ATTR_NULL }; static struct elevator_type iosched_bfq_mq = { .ops.mq = { .get_rq_priv = bfq_get_rq_private, .put_rq_priv = bfq_put_rq_private, .exit_icq = bfq_exit_icq, .insert_requests = bfq_insert_requests, .dispatch_request = bfq_dispatch_request, .next_request = elv_rb_latter_request, .former_request = elv_rb_former_request, .allow_merge = bfq_allow_bio_merge, .bio_merge = bfq_bio_merge, .request_merge = bfq_request_merge, .requests_merged = bfq_requests_merged, .request_merged = bfq_request_merged, .has_work = bfq_has_work, .init_sched = bfq_init_queue, .exit_sched = bfq_exit_queue, }, .uses_mq = true, .icq_size = sizeof(struct bfq_io_cq), .icq_align = __alignof__(struct bfq_io_cq), .elevator_attrs = bfq_attrs, .elevator_name = "bfq", .elevator_owner = THIS_MODULE, }; #ifdef CONFIG_BFQ_GROUP_IOSCHED static struct blkcg_policy blkcg_policy_bfq = { .dfl_cftypes = bfq_blkg_files, .legacy_cftypes = bfq_blkcg_legacy_files, .cpd_alloc_fn = bfq_cpd_alloc, .cpd_init_fn = bfq_cpd_init, .cpd_bind_fn = bfq_cpd_init, .cpd_free_fn = bfq_cpd_free, .pd_alloc_fn = bfq_pd_alloc, .pd_init_fn = bfq_pd_init, .pd_offline_fn = bfq_pd_offline, .pd_free_fn = bfq_pd_free, .pd_reset_stats_fn = bfq_pd_reset_stats, }; #endif static int __init bfq_init(void) { int ret; #ifdef CONFIG_BFQ_GROUP_IOSCHED ret = blkcg_policy_register(&blkcg_policy_bfq); if (ret) return ret; #endif ret = -ENOMEM; if (bfq_slab_setup()) goto err_pol_unreg; /* * Times to load large popular applications for the typical * systems installed on the reference devices (see the * comments before the definitions of the next two * arrays). Actually, we use slightly slower values, as the * estimated peak rate tends to be smaller than the actual * peak rate. The reason for this last fact is that estimates * are computed over much shorter time intervals than the long * intervals typically used for benchmarking. Why? First, to * adapt more quickly to variations. Second, because an I/O * scheduler cannot rely on a peak-rate-evaluation workload to * be run for a long time. */ T_slow[0] = msecs_to_jiffies(3500); /* actually 4 sec */ T_slow[1] = msecs_to_jiffies(6000); /* actually 6.5 sec */ T_fast[0] = msecs_to_jiffies(7000); /* actually 8 sec */ T_fast[1] = msecs_to_jiffies(2500); /* actually 3 sec */ /* * Thresholds that determine the switch between speed classes * (see the comments before the definition of the array * device_speed_thresh). These thresholds are biased towards * transitions to the fast class. This is safer than the * opposite bias. In fact, a wrong transition to the slow * class results in short weight-raising periods, because the * speed of the device then tends to be higher that the * reference peak rate. On the opposite end, a wrong * transition to the fast class tends to increase * weight-raising periods, because of the opposite reason. */ device_speed_thresh[0] = (4 * R_slow[0]) / 3; device_speed_thresh[1] = (4 * R_slow[1]) / 3; ret = elv_register(&iosched_bfq_mq); if (ret) goto err_pol_unreg; return 0; err_pol_unreg: #ifdef CONFIG_BFQ_GROUP_IOSCHED blkcg_policy_unregister(&blkcg_policy_bfq); #endif return ret; } static void __exit bfq_exit(void) { elv_unregister(&iosched_bfq_mq); #ifdef CONFIG_BFQ_GROUP_IOSCHED blkcg_policy_unregister(&blkcg_policy_bfq); #endif bfq_slab_kill(); } module_init(bfq_init); module_exit(bfq_exit); MODULE_AUTHOR("Paolo Valente"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("MQ Budget Fair Queueing I/O Scheduler");