From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f181.google.com (mail-wi0-f181.google.com [209.85.212.181]) by kanga.kvack.org (Postfix) with ESMTP id 4F1346B0032 for ; Tue, 17 Feb 2015 09:37:24 -0500 (EST) Received: by mail-wi0-f181.google.com with SMTP id r20so34028195wiv.2 for ; Tue, 17 Feb 2015 06:37:23 -0800 (PST) Received: from mail-wi0-x22c.google.com (mail-wi0-x22c.google.com. [2a00:1450:400c:c05::22c]) by mx.google.com with ESMTPS id yn4si29362440wjc.16.2015.02.17.06.37.22 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 17 Feb 2015 06:37:22 -0800 (PST) Received: by mail-wi0-f172.google.com with SMTP id l15so33685887wiw.5 for ; Tue, 17 Feb 2015 06:37:22 -0800 (PST) Date: Tue, 17 Feb 2015 15:37:20 +0100 From: Michal Hocko Subject: Re: How to handle TIF_MEMDIE stalls? Message-ID: <20150217143720.GB32017@dhcp22.suse.cz> References: <20141220223504.GI15665@dastard> <201412211745.ECD69212.LQOFHtFOJMSOFV@I-love.SAKURA.ne.jp> <20141229181937.GE32618@dhcp22.suse.cz> <201412301542.JEC35987.FFJFOOQtHLSMVO@I-love.SAKURA.ne.jp> <20141230112158.GA15546@dhcp22.suse.cz> <201502092044.JDG39081.LVFOOtFHQFOMSJ@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201502092044.JDG39081.LVFOOtFHQFOMSJ@I-love.SAKURA.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: david@fromorbit.com, dchinner@redhat.com, linux-mm@kvack.org, rientjes@google.com, oleg@redhat.com, akpm@linux-foundation.org, mgorman@suse.de, hannes@cmpxchg.org, torvalds@linux-foundation.org On Mon 09-02-15 20:44:16, Tetsuo Handa wrote: > Hello. > > Today I tested Linux 3.19 and noticed unexpected behavior (A) (B) > shown below. > > (A) The order-0 __GFP_WAIT allocation fails immediately upon OOM condition > despite we didn't remove the > > /* > * In this implementation, order <= PAGE_ALLOC_COSTLY_ORDER > * means __GFP_NOFAIL, but that may not be true in other > * implementations. > */ > if (order <= PAGE_ALLOC_COSTLY_ORDER) > return 1; > > check in should_alloc_retry(). Is this what you expected? The code before 9879de7373fc (mm: page_alloc: embed OOM killing naturally into allocation slowpath) was looping on this kind of allocation even though GFP_NOFS didn't trigger OOM killer. This change was not intentional I guess but it makes sense on its own. We shouldn't simply loop in a hope that something happens and we finally make a progress. Failing __GFP_WAIT allocation is perfectly fine IMO. Why do you think this is a problem? Btw. this has nothing to do with TIF_MEMDIE and it would be much better to discuss it in a separate thread... > (B) When coredump to pipe is configured, the system stalls under OOM > condition due to memory allocation by coredump's reader side. > How should we handle this "expected to terminate shortly but unable > to terminate due to invisible dependency" case? What approaches > other than applying timeout on coredump's writer side are possible? > (Running inside memory cgroup is not an answer which I want.) This is really nasty and we have discussed that with Oleg some time ago. We have SIGNAL_GROUP_COREDUMP which prevents the OOM killer from selecting the task. The issue seems to be that OOM killer might inherently race with setting the flag. I have no idea what to do about this, unfortunately. Oleg? -- 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