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2019-01-04block: add documentation for io_timeoutWeiping Zhang1-0/+7
Add documentation for /sys/block/<disk>/queue/io_timeout. Reviewed-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Weiping Zhang <zhangweiping@didiglobal.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-16block: update sysfs documentationDamien Le Moal1-1/+28
Add the description of the zoned, nr_zones and chunk_sectors sysfs queue attributes to Documentation/block/queue-sysfs.txt. The description of the zoned and chunk_sector attributes are mostly copied from ABI/testing/sysfs-block (added a typo fix). While at it, also fix a typo in the description of the io_poll_delay attribute. nr_zones description is also added to ABI/testing/sysfs-block and contact email address updated for the zoned attribute. Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-04-08block: remove the discard_zeroes_data flagChristoph Hellwig1-5/+0
Now that we use the proper REQ_OP_WRITE_ZEROES operation everywhere we can kill this hack. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-03-28blk-throttle: make throtl_slice tunableShaohua Li1-0/+6
throtl_slice is important for blk-throttling. It's called slice internally but it really is a time window blk-throttling samples data. blk-throttling will make decision based on the samplings. An example is bandwidth measurement. A cgroup's bandwidth is measured in the time interval of throtl_slice. A small throtl_slice meanse cgroups have smoother throughput but burn more CPUs. It has 100ms default value, which is not appropriate for all disks. A fast SSD can dispatch a lot of IOs in 100ms. This patch makes it tunable. Since throtl_slice isn't a time slice, the sysfs name 'throttle_sample_time' reflects its character better. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-01-03block: fix up io_poll documentationJeff Moyer1-3/+3
/sys/block/<dev>/queue/io_poll is a boolean. Fix the docs. Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-11-28blk-wbt: allow reset of default latency through sysfsJens Axboe1-1/+3
Allow a write of '-1' to reset the default latency target for a given device. This removes knowledge of the different default settings for rotational vs non-rotational from user space. Signed-off-by: Jens Axboe <axboe@fb.com>
2016-11-17block: document the 'io_poll_delay' queue sysfs fileJens Axboe1-0/+14
This was documented in the original commit, 64f1c21e86f7, but it never made it into the proper location for queue sysfs files. Signed-off-by: Jens Axboe <axboe@fb.com>
2016-11-10block: hook up writeback throttlingJens Axboe1-0/+7
Enable throttling of buffered writeback to make it a lot more smooth, and has way less impact on other system activity. Background writeback should be, by definition, background activity. The fact that we flush huge bundles of it at the time means that it potentially has heavy impacts on foreground workloads, which isn't ideal. We can't easily limit the sizes of writes that we do, since that would impact file system layout in the presence of delayed allocation. So just throttle back buffered writeback, unless someone is waiting for it. The algorithm for when to throttle takes its inspiration in the CoDel networking scheduling algorithm. Like CoDel, blk-wb monitors the minimum latencies of requests over a window of time. In that window of time, if the minimum latency of any request exceeds a given target, then a scale count is incremented and the queue depth is shrunk. The next monitoring window is shrunk accordingly. Unlike CoDel, if we hit a window that exhibits good behavior, then we simply increment the scale count and re-calculate the limits for that scale value. This prevents us from oscillating between a close-to-ideal value and max all the time, instead remaining in the windows where we get good behavior. Unlike CoDel, blk-wb allows the scale count to to negative. This happens if we primarily have writes going on. Unlike positive scale counts, this doesn't change the size of the monitoring window. When the heavy writers finish, blk-bw quickly snaps back to it's stable state of a zero scale count. The patch registers a sysfs entry, 'wb_lat_usec'. This sets the latency target to me met. It defaults to 2 msec for non-rotational storage, and 75 msec for rotational storage. Setting this value to '0' disables blk-wb. Generally, a user would not have to touch this setting. We don't enable WBT on devices that are managed with CFQ, and have a non-root block cgroup attached. If we have a proportional share setup on this particular disk, then the wbt throttling will interfere with that. We don't have a strong need for wbt for that case, since we will rely on CFQ doing that for us. Signed-off-by: Jens Axboe <axboe@fb.com>
2016-08-11doc: update block/queue-sysfs.txt entriesJoe Lawrence1-0/+18
Add descriptions for dax, io_poll, and write_same_max_bytes files. Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-06-28Doc: block: Fix a typo in queue-sysfs.txtMasanari Iida1-1/+1
This patch fix a spelling typo found in queue-sysfs.txt. Signed-off-by: Masanari Iida <standby24x7@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-04-12block: add ability to flag write back caching on a deviceJens Axboe1-0/+9
Add an internal helper and flag for setting whether a queue has write back caching, or write through (or none). Add a sysfs file to show this as well, and make it changeable from user space. This will replace the (awkward) blk_queue_flush() interface that drivers currently use to inform the block layer of write cache state and capabilities. Signed-off-by: Jens Axboe <axboe@fb.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
2015-07-17block: make /sys/block/<dev>/queue/discard_max_bytes writeableJens Axboe1-1/+9
Lots of devices support huge discard sizes these days. Depending on how the device handles them internally, huge discards can introduce massive latencies (hundreds of msec) on the device side. We have a sysfs file, discard_max_bytes, that advertises the max hardware supported discard size. Make this writeable, and split the settings into a soft and hard limit. This can be set from 'discard_granularity' and up to the hardware limit. Add a new sysfs file, 'discard_max_hw_bytes', that shows the hw set limit. Reviewed-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-08-28doc: queue-sysfs: minor fixesArnd Hannemann1-3/+3
This patches fixes a typo, and for consistency use "IO" in upper case in the block/queue-sysfs.txt documentation. Signed-off-by: Arnd Hannemann <arnd@arndnet.de> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2013-05-28doc: fix misspellings with 'codespell' toolAnatol Pomozov1-1/+1
Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2012-08-09Documentation: update tunable options in block/cfq-iosched.txtNamjae Jeon1-0/+64
Update tunable options in block/cfq-iosched.txt. Signed-off-by: Namjae Jeon <linkinjeon@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-26blkcg: implement per-blkg request allocationTejun Heo1-0/+7
Currently, request_queue has one request_list to allocate requests from regardless of blkcg of the IO being issued. When the unified request pool is used up, cfq proportional IO limits become meaningless - whoever grabs the next request being freed wins the race regardless of the configured weights. This can be easily demonstrated by creating a blkio cgroup w/ very low weight, put a program which can issue a lot of random direct IOs there and running a sequential IO from a different cgroup. As soon as the request pool is used up, the sequential IO bandwidth crashes. This patch implements per-blkg request_list. Each blkg has its own request_list and any IO allocates its request from the matching blkg making blkcgs completely isolated in terms of request allocation. * Root blkcg uses the request_list embedded in each request_queue, which was renamed to @q->root_rl from @q->rq. While making blkcg rl handling a bit harier, this enables avoiding most overhead for root blkcg. * Queue fullness is properly per request_list but bdi isn't blkcg aware yet, so congestion state currently just follows the root blkcg. As writeback isn't aware of blkcg yet, this works okay for async congestion but readahead may get the wrong signals. It's better than blkcg completely collapsing with shared request_list but needs to be improved with future changes. * After this change, each block cgroup gets a full request pool making resource consumption of each cgroup higher. This makes allowing non-root users to create cgroups less desirable; however, note that allowing non-root users to directly manage cgroups is already severely broken regardless of this patch - each block cgroup consumes kernel memory and skews IO weight (IO weights are not hierarchical). v2: queue-sysfs.txt updated and patch description udpated as suggested by Vivek. v3: blk_get_rl() wasn't checking error return from blkg_lookup_create() and may cause oops on lookup failure. Fix it by falling back to root_rl on blkg lookup failures. This problem was spotted by Rakesh Iyer <rni@google.com>. v4: Updated to accomodate 458f27a982 "block: Avoid missed wakeup in request waitqueue". blk_drain_queue() now wakes up waiters on all blkg->rl on the target queue. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-07-23block: strict rq_affinityDan Williams1-3/+7
Some systems benefit from completions always being steered to the strict requester cpu rather than the looser "per-socket" steering that blk_cpu_to_group() attempts by default. This is because the first CPU in the group mask ends up being completely overloaded with work, while the others (including the original submitter) has power left to spare. Allow the strict mode to be set by writing '2' to the sysfs control file. This is identical to the scheme used for the nomerges file, where '2' is a more aggressive setting than just being turned on. echo 2 > /sys/block/<bdev>/queue/rq_affinity Cc: Christoph Hellwig <hch@infradead.org> Cc: Roland Dreier <roland@purestorage.com> Tested-by: Dave Jiang <dave.jiang@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-01-29block: Added in stricter no merge semantics for block I/OAlan D. Brunelle1-5/+5
Updated 'nomerges' tunable to accept a value of '2' - indicating that _no_ merges at all are to be attempted (not even the simple one-hit cache). The following table illustrates the additional benefit - 5 minute runs of a random I/O load were applied to a dozen devices on a 16-way x86_64 system. nomerges Throughput %System Improvement (tput / %sys) -------- ------------ ----------- ------------------------- 0 12.45 MB/sec 0.669365609 1 12.50 MB/sec 0.641519199 0.40% / 2.71% 2 12.52 MB/sec 0.639849750 0.56% / 2.96% Signed-off-by: Alan D. Brunelle <alan.brunelle@hp.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-02-02block: add text file detailing queue/ sysfs filesJens Axboe1-0/+63
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>