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 23A0A6B0253 for ; Tue, 25 Aug 2015 11:26:55 -0400 (EDT) Received: by wijp15 with SMTP id p15so19528354wij.0 for ; Tue, 25 Aug 2015 08:26:54 -0700 (PDT) Received: from mail-wi0-f176.google.com (mail-wi0-f176.google.com. [209.85.212.176]) by mx.google.com with ESMTPS id jd10si2199791wjb.208.2015.08.25.08.26.53 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Aug 2015 08:26:53 -0700 (PDT) Received: by wijp15 with SMTP id p15so19527707wij.0 for ; Tue, 25 Aug 2015 08:26:53 -0700 (PDT) Date: Tue, 25 Aug 2015 17:26:51 +0200 From: Michal Hocko Subject: Re: [patch -mm] mm, oom: add global access to memory reserves on livelock Message-ID: <20150825152650.GI6285@dhcp22.suse.cz> References: <20150821081745.GG23723@dhcp22.suse.cz> <201508212229.GIC00036.tVFMQLOOFJOFSH@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Tetsuo Handa , akpm@linux-foundation.org, mgorman@suse.de, hannes@cmpxchg.org, oleg@redhat.com, vbabka@suse.cz, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Mon 24-08-15 14:10:10, David Rientjes wrote: > On Fri, 21 Aug 2015, Tetsuo Handa wrote: > > > Why can't we think about choosing more OOM victims instead of granting access > > to memory reserves? > > > > We have no indication of which thread is holding a mutex that would need > to be killed, so we'd be randomly killing processes waiting for forward > progress. A worst-case scenario would be the thread is OOM_DISABLE and we > kill every process on the system needlessly. This problem obviously > occurs often enough that killing all userspace isnt going to be a viable > solution. > > > Also, SysRq might not be usable under OOM because workqueues can get stuck. > > The panic_on_oom_timeout was first proposed using a workqueue but was > > updated to use a timer because there is no guarantee that workqueues work > > as expected under OOM. > > > > I don't know anything about a panic_on_oom_timeout, You were CCed on the discussion http://lkml.kernel.org/r/20150609170310.GA8990%40dhcp22.suse.cz > but panicking would > only be a reasonable action if memory reserves were fully depleted. That > could easily be dealt with in the page allocator so there's no timeout > involved. As noted in other email. Just depletion is not a good indicator. The system can still make a forward progress even when reserves are depleted. -- 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