From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755896AbbHYP13 (ORCPT ); Tue, 25 Aug 2015 11:27:29 -0400 Received: from mail-wi0-f175.google.com ([209.85.212.175]:36317 "EHLO mail-wi0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755625AbbHYP0y (ORCPT ); Tue, 25 Aug 2015 11:26:54 -0400 Date: Tue, 25 Aug 2015 17:26:51 +0200 From: Michal Hocko 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 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: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.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