From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id E564C6B0261 for ; Tue, 26 Apr 2016 10:04:38 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id s63so13228863wme.2 for ; Tue, 26 Apr 2016 07:04:38 -0700 (PDT) Received: from mail-wm0-f66.google.com (mail-wm0-f66.google.com. [74.125.82.66]) by mx.google.com with ESMTPS id wt3si30107208wjb.215.2016.04.26.07.04.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Apr 2016 07:04:37 -0700 (PDT) Received: by mail-wm0-f66.google.com with SMTP id w143so4729572wmw.3 for ; Tue, 26 Apr 2016 07:04:37 -0700 (PDT) From: Michal Hocko Subject: [PATCH 1/2] mm, oom_reaper: hide oom reaped tasks from OOM killer more carefully Date: Tue, 26 Apr 2016 16:04:29 +0200 Message-Id: <1461679470-8364-2-git-send-email-mhocko@kernel.org> In-Reply-To: <1461679470-8364-1-git-send-email-mhocko@kernel.org> References: <1461679470-8364-1-git-send-email-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Tetsuo Handa , David Rientjes , linux-mm@kvack.org, LKML , Michal Hocko From: Michal Hocko 36324a990cf5 ("oom: clear TIF_MEMDIE after oom_reaper managed to unmap the address space") not only clears TIF_MEMDIE for oom reaped task but also set OOM_SCORE_ADJ_MIN for the target task to hide it from the oom killer. This works in simple cases but it is not sufficient for (unlikely) cases where the mm is shared between independent processes (as they do not share signal struct). If the mm had only small amount of memory which could be reaped then another task sharing the mm could be selected and that wouldn't help to move out from the oom situation. Introduce MMF_OOM_REAPED mm flag which is checked in oom_badness (same as OOM_SCORE_ADJ_MIN) and task is skipped if the flag is set. Set the flag after __oom_reap_task is done with a task. This will force the select_bad_process() to ignore all already oom reaped tasks as well as no such task is sacrificed for its parent. Signed-off-by: Michal Hocko --- include/linux/sched.h | 1 + mm/oom_kill.c | 9 +++++++-- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index acfc32b30704..7bd0fa9db199 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -512,6 +512,7 @@ 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_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 415f7eb913fa..c0376efa79ec 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -174,8 +174,13 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, if (!p) return 0; + /* + * Do not even consider tasks which are explicitly marked oom + * unkillable or have been already oom reaped. + */ adj = (long)p->signal->oom_score_adj; - if (adj == OOM_SCORE_ADJ_MIN) { + if (adj == OOM_SCORE_ADJ_MIN || + test_bit(MMF_OOM_REAPED, &p->mm->flags)) { task_unlock(p); return 0; } @@ -513,7 +518,7 @@ static bool __oom_reap_task(struct task_struct *tsk) * This task can be safely ignored because we cannot do much more * to release its memory. */ - tsk->signal->oom_score_adj = OOM_SCORE_ADJ_MIN; + set_bit(MMF_OOM_REAPED, &mm->flags); out: mmput(mm); return ret; -- 2.8.0.rc3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org