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From: Michal Hocko <mhocko@kernel.org>
To: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	Oleg Nesterov <oleg@redhat.com>,
	David Rientjes <rientjes@google.com>,
	Vladimir Davydov <vdavydov@parallels.com>,
	Michal Hocko <mhocko@suse.com>
Subject: [PATCH v2 2/9] mm,oom_reaper: Do not attempt to reap a task twice.
Date: Thu, 25 Aug 2016 12:03:07 +0200
Message-ID: <1472119394-11342-3-git-send-email-mhocko@kernel.org> (raw)
In-Reply-To: <1472119394-11342-1-git-send-email-mhocko@kernel.org>

From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

"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.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 include/linux/sched.h |  1 -
 mm/oom_kill.c         | 15 +++------------
 2 files changed, 3 insertions(+), 13 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index d7e1e783cf01..f9b0b2dd4f18 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -522,7 +522,6 @@ 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)
 
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 87fad956c96b..45097f5a8f30 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -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:
-- 
2.8.1

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  parent reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-25 10:03 [PATCH v2 0/10] fortify oom killer even more Michal Hocko
2016-08-25 10:03 ` [PATCH v2 1/9] mm,oom_reaper: Reduce find_lock_task_mm() usage Michal Hocko
2016-08-25 10:03 ` Michal Hocko [this message]
2016-08-25 10:03 ` [PATCH v2 3/9] oom: keep mm of the killed task available Michal Hocko
2016-08-25 10:03 ` [PATCH v2 4/9] kernel, oom: fix potential pgd_lock deadlock from __mmdrop Michal Hocko
2016-08-25 10:03 ` [PATCH v2 5/9] mm, oom: get rid of signal_struct::oom_victims Michal Hocko
2016-08-25 10:03 ` [PATCH v2 6/9] oom, suspend: fix oom_killer_disable vs. pm suspend properly Michal Hocko
2016-08-25 10:03 ` [PATCH v2 7/9] mm, oom: enforce exit_oom_victim on current task Michal Hocko
2016-08-25 10:03 ` [PATCH v2 8/9] mm: make sure that kthreads will not refault oom reaped memory Michal Hocko
2016-08-25 10:03 ` [PATCH v2 9/9] oom, oom_reaper: allow to reap mm shared by the kthreads Michal Hocko

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