mm,oom_reaper: do not attempt to reap a task twice (8496afab) · Commits · 戴 / test

"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>

include/linux/sched.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -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)

mm/oom_kill.c

+3 −12

Original line number	Diff line number	Diff line
		@@ -578,20 +578,11 @@ static void oom_reap_task(struct task_struct *tsk)
		if (attempts <= MAX_OOM_REAP_RETRIES)
		goto done;

		pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
		task_pid_nr(tsk), tsk->comm);
		/* Ignore this mm because somebody can't call up_write(mmap_sem). */
		set_bit(MMF_OOM_REAPED, &mm->flags);

		/*
		* 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",
		pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
		task_pid_nr(tsk), tsk->comm);
		set_bit(MMF_OOM_REAPED, &mm->flags);
		}
		debug_show_all_locks();

		done:

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