From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754801Ab3LQQXp (ORCPT ); Tue, 17 Dec 2013 11:23:45 -0500 Received: from cantor2.suse.de ([195.135.220.15]:59641 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753185Ab3LQQXn (ORCPT ); Tue, 17 Dec 2013 11:23:43 -0500 Date: Tue, 17 Dec 2013 17:23:42 +0100 From: Michal Hocko To: David Rientjes Cc: Johannes Weiner , Andrew Morton , KAMEZAWA Hiroyuki , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org Subject: Re: [patch 1/2] mm, memcg: avoid oom notification when current needs access to memory reserves Message-ID: <20131217162342.GG28991@dhcp22.suse.cz> References: <20131204111318.GE8410@dhcp22.suse.cz> <20131209124840.GC3597@dhcp22.suse.cz> <20131210103827.GB20242@dhcp22.suse.cz> <20131211095549.GA18741@dhcp22.suse.cz> <20131212103159.GB2630@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 13-12-13 15:55:44, David Rientjes wrote: > On Thu, 12 Dec 2013, Michal Hocko wrote: [...] > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index c72b03bf9679..fee25c5934d2 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -2692,7 +2693,8 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, > > * MEMDIE process. > > */ > > if (unlikely(test_thread_flag(TIF_MEMDIE) > > - || fatal_signal_pending(current))) > > + || fatal_signal_pending(current)) > > + || current->flags & PF_EXITING) > > goto bypass; > > > > if (unlikely(task_in_memcg_oom(current))) > > > > rather than the later checks down the oom_synchronize paths. The comment > > already mentions dying process... > > > > This is scary because it doesn't even try to reclaim memcg memory before > allowing the allocation to succeed. Why should it reclaim in the first place when it simply is on the way to release memory. In other words why should it increase the memory pressure when it is in fact releasing it? I am really puzzled here. On one hand you are strongly arguing for not notifying when we know we can prevent from OOM action and on the other hand you are ok to get vmpressure/thresholds notification when an exiting task triggers reclaim. So I am really lost in what you are trying to achieve here. It sounds a bit arbirtrary. > I think we could even argue that we should move the > fatal_signal_pending(current) check to later and the only condition we > should really be bypassing here is TIF_MEMDIE since it will only get > set when reclaim has already failed. Any arguments? -- Michal Hocko SUSE Labs