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mm,oom_reaper: do not attempt to reap a task twice

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"mm, oom_reaper: do not attempt to reap a task twice" tried to give the
OOM reaper one more chance to retry using MMF_OOM_NOT_REAPABLE flag.
But the usefulness of the flag is rather limited and actually never
shown in practice.  If the flag is set, it means that the holder of
mm->mmap_sem cannot call up_write() due to presumably being blocked at
unkillable wait waiting for other thread's memory allocation.  But since
one of threads sharing that mm will queue that mm immediately via
task_will_free_mem() shortcut (otherwise, oom_badness() will select the
same mm again due to oom_score_adj value unchanged), retrying
MMF_OOM_NOT_REAPABLE mm is unlikely helpful.

Let's always set MMF_OOM_REAPED.

Link: http://lkml.kernel.org/r/1472119394-11342-3-git-send-email-mhocko@kernel.org
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Tetsuo Handa 2016-10-07 16:58:48 -07:00 committed by Linus Torvalds
parent 7ebffa4555
commit 8496afaba9
2 changed files with 3 additions and 13 deletions
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1
include/linux/sched.h
View File

@ -525,7 +525,6 @@ static inline int get_dumpable(struct mm_struct *mm)
#define MMF_HAS_UPROBES 19 /* has uprobes */
#define MMF_RECALC_UPROBES 20 /* MMF_HAS_UPROBES can be wrong */
#define MMF_OOM_REAPED 21 /* mm has been already reaped */
#define MMF_OOM_NOT_REAPABLE 22 /* mm couldn't be reaped */
#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK)

15
mm/oom_kill.c
View File

@ -578,20 +578,11 @@ static void oom_reap_task(struct task_struct *tsk)
if (attempts <= MAX_OOM_REAP_RETRIES)
goto done;
/* Ignore this mm because somebody can't call up_write(mmap_sem). */
set_bit(MMF_OOM_REAPED, &mm->flags);
pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
task_pid_nr(tsk), tsk->comm);
/*
* If we've already tried to reap this task in the past and
* failed it probably doesn't make much sense to try yet again
* so hide the mm from the oom killer so that it can move on
* to another task with a different mm struct.
*/
if (test_and_set_bit(MMF_OOM_NOT_REAPABLE, &mm->flags)) {
pr_info("oom_reaper: giving up pid:%d (%s)\n",
task_pid_nr(tsk), tsk->comm);
set_bit(MMF_OOM_REAPED, &mm->flags);
}
debug_show_all_locks();
done: