linux/mm/oom_kill.c, branch v2.6.31-rc2

oom: only oom kill exiting tasks with attached memory

2009-06-17T02:47:45Z

When a task is chosen for oom kill and is found to be PF_EXITING, __oom_kill_task() is called to elevate the task's timeslice and give it access to memory reserves so that it may quickly exit. This privilege is unnecessary, however, if the task has already detached its mm. Although its possible for the mm to become detached later since task_lock() is not held, __oom_kill_task() will simply be a no-op in such circumstances. Subsequently, it is no longer necessary to warn about killing mm-less tasks since it is a no-op. Signed-off-by: David Rientjes Acked-by: Rik van Riel Cc: Balbir Singh Cc: Minchan Kim Reviewed-by: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

oom: avoid unnecessary mm locking and scanning for OOM_DISABLE

2009-06-17T02:47:43Z

This moves the check for OOM_DISABLE to the badness heuristic so it is only necessary to hold task_lock() once. If the mm is OOM_DISABLE, the score is 0, which is also correctly exported via /proc/pid/oom_score. This requires that tasks with badness scores of 0 are prohibited from being oom killed, which makes sense since they would not allow for future memory freeing anyway. Since the oom_adj value is a characteristic of an mm and not a task, it is no longer necessary to check the oom_adj value for threads sharing the same memory (except when simply issuing SIGKILLs for threads in other thread groups). Cc: Nick Piggin Cc: Rik van Riel Cc: Mel Gorman Signed-off-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

oom: move oom_adj value from task_struct to mm_struct

2009-06-17T02:47:43Z

The per-task oom_adj value is a characteristic of its mm more than the task itself since it's not possible to oom kill any thread that shares the mm. If a task were to be killed while attached to an mm that could not be freed because another thread were set to OOM_DISABLE, it would have needlessly been terminated since there is no potential for future memory freeing. This patch moves oomkilladj (now more appropriately named oom_adj) from struct task_struct to struct mm_struct. This requires task_lock() on a task to check its oom_adj value to protect against exec, but it's already necessary to take the lock when dereferencing the mm to find the total VM size for the badness heuristic. This fixes a livelock if the oom killer chooses a task and another thread sharing the same memory has an oom_adj value of OOM_DISABLE. This occurs because oom_kill_task() repeatedly returns 1 and refuses to kill the chosen task while select_bad_process() will repeatedly choose the same task during the next retry. Taking task_lock() in select_bad_process() to check for OOM_DISABLE and in oom_kill_task() to check for threads sharing the same memory will be removed in the next patch in this series where it will no longer be necessary. Writing to /proc/pid/oom_adj for a kthread will now return -EINVAL since these threads are immune from oom killing already. They simply report an oom_adj value of OOM_DISABLE. Cc: Nick Piggin Cc: Rik van Riel Cc: Mel Gorman Signed-off-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

oom: fix possible oom_dump_tasks NULL pointer

2009-05-29T15:40:01Z

When /proc/sys/vm/oom_dump_tasks is enabled, it is possible to get a NULL pointer for tasks that have detached mm's since task_lock() is not held during the tasklist scan. Add the task_lock(). Acked-by: Nick Piggin Acked-by: Mel Gorman Cc: Rik van Riel Signed-off-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

oom: prevent livelock when oom_kill_allocating_task is set

2009-05-06T23:36:09Z

When /proc/sys/vm/oom_kill_allocating_task is set for large systems that want to avoid the lengthy tasklist scan, it's possible to livelock if current is ineligible for oom kill. This normally happens when it is set to OOM_DISABLE, but is also possible if any threads are sharing the same ->mm with a different tgid. So change __out_of_memory() to fall back to the full task-list scan if it was unable to kill `current'. Cc: Nick Piggin Signed-off-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memcg: show memcg information during OOM

2009-04-03T02:04:55Z

Add RSS and swap to OOM output from memcg Display memcg values like failcnt, usage and limit when an OOM occurs due to memcg. Thanks to Johannes Weiner, Li Zefan, David Rientjes, Kamezawa Hiroyuki, Daisuke Nishimura and KOSAKI Motohiro for review. Sample output ------------- Task in /a/x killed as a result of limit of /a memory: usage 1048576kB, limit 1048576kB, failcnt 4183 memory+swap: usage 1400964kB, limit 9007199254740991kB, failcnt 0 [akpm@linux-foundation.org: compilation fix] [akpm@linux-foundation.org: fix kerneldoc and whitespace] [akpm@linux-foundation.org: add printk facility level] Signed-off-by: Balbir Singh Cc: KAMEZAWA Hiroyuki Cc: Daisuke Nishimura Cc: Li Zefan Cc: Paul Menage Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

oom_kill: don't call for int_sqrt(0)

2009-04-01T15:59:11Z

There is no need to call for int_sqrt if argument is 0. Signed-off-by: Cyrill Gorcunov Cc: Pekka Enberg Cc: Christoph Lameter Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memcg: avoid deadlock caused by race between oom and cpuset_attach

2009-01-08T16:31:09Z

mpol_rebind_mm(), which can be called from cpuset_attach(), does down_write(mm->mmap_sem). This means down_write(mm->mmap_sem) can be called under cgroup_mutex. OTOH, page fault path does down_read(mm->mmap_sem) and calls mem_cgroup_try_charge_xxx(), which may eventually calls mem_cgroup_out_of_memory(). And mem_cgroup_out_of_memory() calls cgroup_lock(). This means cgroup_lock() can be called under down_read(mm->mmap_sem). If those two paths race, deadlock can happen. This patch avoid this deadlock by: - remove cgroup_lock() from mem_cgroup_out_of_memory(). - define new mutex (memcg_tasklist) and serialize mem_cgroup_move_task() (->attach handler of memory cgroup) and mem_cgroup_out_of_memory. Signed-off-by: Daisuke Nishimura Reviewed-by: KAMEZAWA Hiroyuki Acked-by: Balbir Singh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memcg: avoid unnecessary system-wide-oom-killer

2009-01-08T16:31:06Z

Current mmtom has new oom function as pagefault_out_of_memory(). It's added for select bad process rathar than killing current. When memcg hit limit and calls OOM at page_fault, this handler called and system-wide-oom handling happens. (means kernel panics if panic_on_oom is true....) To avoid overkill, check memcg's recent behavior before starting system-wide-oom. And this patch also fixes to guarantee "don't accnout against process with TIF_MEMDIE". This is necessary for smooth OOM. [akpm@linux-foundation.org: build fix] Signed-off-by: KAMEZAWA Hiroyuki Cc: Li Zefan Cc: Balbir Singh Cc: Daisuke Nishimura Cc: Badari Pulavarty Cc: Jan Blunck Cc: Hirokazu Takahashi Cc: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

oom: print triggering task's cpuset and mems allowed

2009-01-06T23:58:59Z

When cpusets are enabled, it's necessary to print the triggering task's set of allowable nodes so the subsequently printed meminfo can be interpreted correctly. We also print the task's cpuset name for informational purposes. [rientjes@google.com: task lock current before dereferencing cpuset] Cc: Paul Menage Cc: Li Zefan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds