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 CBD4B6B025E for ; Thu, 8 Dec 2016 08:32:33 -0500 (EST) Received: by mail-wm0-f69.google.com with SMTP id a20so6295828wme.5 for ; Thu, 08 Dec 2016 05:32:33 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id z2si29343099wjz.7.2016.12.08.05.32.32 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 08 Dec 2016 05:32:32 -0800 (PST) Date: Thu, 8 Dec 2016 14:32:30 +0100 From: Michal Hocko Subject: Re: [PATCH] mm/page_alloc: Wait for oom_lock before retrying. Message-ID: <20161208133229.GB26530@dhcp22.suse.cz> References: <1481020439-5867-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20161207081555.GB17136@dhcp22.suse.cz> <201612080029.IBD55588.OSOFOtHVMLQFFJ@I-love.SAKURA.ne.jp> <5c3ddf50-ca19-2cae-a3ce-b10eafe8363c@suse.cz> <201612082000.FBB00003.FFMQSVHJOFLOtO@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201612082000.FBB00003.FFMQSVHJOFLOtO@I-love.SAKURA.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: vbabka@suse.cz, linux-mm@kvack.org, hannes@cmpxchg.org, rientjes@google.com, aarcange@redhat.com, david@fromorbit.com, sergey.senozhatsky@gmail.com, akpm@linux-foundation.org On Thu 08-12-16 20:00:39, Tetsuo Handa wrote: > Cc'ing people involved in commit dc56401fc9f25e8f ("mm: oom_kill: simplify > OOM killer locking") and Sergey as printk() expert. Topic started from > http://lkml.kernel.org/r/1481020439-5867-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp . > > Vlastimil Babka wrote: > > > May I? Something like below? With patch below, the OOM killer can send > > > SIGKILL smoothly and printk() can report smoothly (the frequency of > > > "** XXX printk messages dropped **" messages is significantly reduced). > > > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > index 2c6d5f6..ee0105b 100644 > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -3075,7 +3075,7 @@ void warn_alloc(gfp_t gfp_mask, const char *fmt, ...) > > > * Acquire the oom lock. If that fails, somebody else is > > > * making progress for us. > > > */ > > > > The comment above could use some updating then. Although maybe "somebody > > killed us" is also technically "making progress for us" :) > > I think we can update the comment. But since __GFP_KILLABLE does not exist, > SIGKILL is pending does not imply that current thread will make progress by > leaving the retry loop immediately. Therefore, Although this is true I do not think that cluttering the code with this case is anyhow useful. In the vast majority of cases SIGKILL pending will be a result of the oom killer. [...] > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 6de9440..6c43d8e 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3037,12 +3037,16 @@ void warn_alloc(gfp_t gfp_mask, const char *fmt, ...) > *did_some_progress = 0; > > /* > - * Acquire the oom lock. If that fails, somebody else is > - * making progress for us. > + * Give the OOM killer enough CPU time for sending SIGKILL. > + * Do not return without a short sleep unless TIF_MEMDIE is set, for > + * currently tsk_is_oom_victim(current) == true does not make > + * gfp_pfmemalloc_allowed() == true via TIF_MEMDIE until > + * mark_oom_victim(current) is called. > */ > - if (!mutex_trylock(&oom_lock)) { > + if (mutex_lock_killable(&oom_lock)) { > *did_some_progress = 1; > - schedule_timeout_uninterruptible(1); > + if (!test_thread_flag(TIF_MEMDIE)) > + schedule_timeout_uninterruptible(1); I am not really sure this is necessary. Just return outside and for those unlikely cases where the current task was killed before entering the page allocator simply do not matter imho. I would rather go with simplicity here. > return NULL; > } > > -- > 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