Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934065Ab2JLNCC (ORCPT ); Fri, 12 Oct 2012 09:02:02 -0400 Received: from cantor2.suse.de ([195.135.220.15]:44394 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933615Ab2JLNCA (ORCPT ); Fri, 12 Oct 2012 09:02:00 -0400 Date: Fri, 12 Oct 2012 15:01:59 +0200 From: Michal Hocko To: KOSAKI Motohiro Cc: Andrew Morton , linux-mm@kvack.org, David Rientjes , KAMEZAWA Hiroyuki , Johannes Weiner , LKML Subject: Re: [PATCH] memcg: oom: fix totalpages calculation for memory.swappiness==0 Message-ID: <20121012130159.GB22083@dhcp22.suse.cz> References: <20121011085038.GA29295@dhcp22.suse.cz> <1349945859-1350-1-git-send-email-mhocko@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 Content-Length: 1733 Lines: 39 On Thu 11-10-12 18:36:26, KOSAKI Motohiro wrote: > On Thu, Oct 11, 2012 at 4:57 AM, Michal Hocko wrote: > > oom_badness takes totalpages argument which says how many pages are > > available and it uses it as a base for the score calculation. The value > > is calculated by mem_cgroup_get_limit which considers both limit and > > total_swap_pages (resp. memsw portion of it). > > > > This is usually correct but since fe35004f (mm: avoid swapping out > > with swappiness==0) we do not swap when swappiness is 0 which means > > that we cannot really use up all the totalpages pages. This in turn > > confuses oom score calculation if the memcg limit is much smaller than > > the available swap because the used memory (capped by the limit) is > > negligible comparing to totalpages so the resulting score is too small > > if adj!=0 (typically task with CAP_SYS_ADMIN or non zero oom_score_adj). > > A wrong process might be selected as result. > > > > The same issue exists for the global oom killer as well but it is not > > that problematic as the amount of the RAM is usually much bigger than > > the swap space. > > > > The problem can be worked around by checking mem_cgroup_swappiness==0 > > and not considering swap at all in such a case. > > > > Signed-off-by: Michal Hocko > > Acked-by: David Rientjes > > Cc: stable [3.5+] > > Acked-by: KOSAKI Motohiro Thanks! -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/