From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id 4E1156B0005 for ; Mon, 11 Jul 2016 08:15:53 -0400 (EDT) Received: by mail-wm0-f72.google.com with SMTP id r190so54465478wmr.0 for ; Mon, 11 Jul 2016 05:15:53 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id j73si8500917wmj.93.2016.07.11.05.15.52 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 11 Jul 2016 05:15:52 -0700 (PDT) Date: Mon, 11 Jul 2016 14:15:51 +0200 From: Michal Hocko Subject: Re: [PATCH 2/6] mm,oom_reaper: Do not attempt to reap a task twice. Message-ID: <20160711121550.GE1811@dhcp22.suse.cz> References: <201607080058.BFI87504.JtFOOFQFVHSLOM@I-love.SAKURA.ne.jp> <201607080101.CCE57351.tQFOOVOFJSHMLF@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201607080101.CCE57351.tQFOOVOFJSHMLF@I-love.SAKURA.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: linux-mm@kvack.org, akpm@linux-foundation.org, oleg@redhat.com, rientjes@google.com, vdavydov@parallels.com, mst@redhat.com On Fri 08-07-16 01:01:36, Tetsuo Handa wrote: > >From 50b3a862b136c783be6ce25e0f22446f15a0ab03 Mon Sep 17 00:00:00 2001 > From: Tetsuo Handa > Date: Fri, 8 Jul 2016 00:28:50 +0900 > Subject: [PATCH 2/6] mm,oom_reaper: Do not attempt to reap a task twice. > > "mm, oom_reaper: do not attempt to reap a task twice" tried to give > OOM reaper one more chance to retry. But since OOM killer or one of > threads sharing that mm will queue that mm immediately, retrying > MMF_OOM_NOT_REAPABLE mm is unlikely helpful. I agree that the usefulness of the flag is rather limited and actually never shown in practice. Considering it was added as a just-in-case measure it is really hard to reason about. And I believe this should be stated in the changelog. > Let's always set MMF_OOM_REAPED. > > Signed-off-by: Tetsuo Handa That being said, feel free to add my Acked-by after the changelog is more clear about the motivation. > --- > 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 553af29..c0efd80 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -523,7 +523,6 @@ 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 951eb1b..9f0022e 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -567,20 +567,11 @@ 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: > -- > 1.8.3.1 -- Michal Hocko SUSE Labs -- 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