diff options
Diffstat (limited to 'mm/util.c')
| -rw-r--r-- | mm/util.c | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/mm/util.c b/mm/util.c index 4fb14ca5a419..47a57e557614 100644 --- a/mm/util.c +++ b/mm/util.c @@ -396,6 +396,13 @@ int __page_mapcount(struct page *page) } EXPORT_SYMBOL_GPL(__page_mapcount); +int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS; +int sysctl_overcommit_ratio __read_mostly = 50; +unsigned long sysctl_overcommit_kbytes __read_mostly; +int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT; +unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */ +unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */ + int overcommit_ratio_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) @@ -437,6 +444,123 @@ unsigned long vm_commit_limit(void) return allowed; } +/* + * Make sure vm_committed_as in one cacheline and not cacheline shared with + * other variables. It can be updated by several CPUs frequently. + */ +struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp; + +/* + * The global memory commitment made in the system can be a metric + * that can be used to drive ballooning decisions when Linux is hosted + * as a guest. On Hyper-V, the host implements a policy engine for dynamically + * balancing memory across competing virtual machines that are hosted. + * Several metrics drive this policy engine including the guest reported + * memory commitment. + */ +unsigned long vm_memory_committed(void) +{ + return percpu_counter_read_positive(&vm_committed_as); +} +EXPORT_SYMBOL_GPL(vm_memory_committed); + +/* + * Check that a process has enough memory to allocate a new virtual + * mapping. 0 means there is enough memory for the allocation to + * succeed and -ENOMEM implies there is not. + * + * We currently support three overcommit policies, which are set via the + * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting + * + * Strict overcommit modes added 2002 Feb 26 by Alan Cox. + * Additional code 2002 Jul 20 by Robert Love. + * + * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise. + * + * Note this is a helper function intended to be used by LSMs which + * wish to use this logic. + */ +int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) +{ + long free, allowed, reserve; + + VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) < + -(s64)vm_committed_as_batch * num_online_cpus(), + "memory commitment underflow"); + + vm_acct_memory(pages); + + /* + * Sometimes we want to use more memory than we have + */ + if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS) + return 0; + + if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) { + free = global_page_state(NR_FREE_PAGES); + free += global_page_state(NR_FILE_PAGES); + + /* + * shmem pages shouldn't be counted as free in this + * case, they can't be purged, only swapped out, and + * that won't affect the overall amount of available + * memory in the system. + */ + free -= global_page_state(NR_SHMEM); + + free += get_nr_swap_pages(); + + /* + * Any slabs which are created with the + * SLAB_RECLAIM_ACCOUNT flag claim to have contents + * which are reclaimable, under pressure. The dentry + * cache and most inode caches should fall into this + */ + free += global_page_state(NR_SLAB_RECLAIMABLE); + + /* + * Leave reserved pages. The pages are not for anonymous pages. + */ + if (free <= totalreserve_pages) + goto error; + else + free -= totalreserve_pages; + + /* + * Reserve some for root + */ + if (!cap_sys_admin) + free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10); + + if (free > pages) + return 0; + + goto error; + } + + allowed = vm_commit_limit(); + /* + * Reserve some for root + */ + if (!cap_sys_admin) + allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10); + + /* + * Don't let a single process grow so big a user can't recover + */ + if (mm) { + reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10); + allowed -= min_t(long, mm->total_vm / 32, reserve); + } + + if (percpu_counter_read_positive(&vm_committed_as) < allowed) + return 0; +error: + vm_unacct_memory(pages); + + return -ENOMEM; +} + /** * get_cmdline() - copy the cmdline value to a buffer. * @task: the task whose cmdline value to copy. |