Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759515Ab2JKWgt (ORCPT ); Thu, 11 Oct 2012 18:36:49 -0400 Received: from mail-oa0-f46.google.com ([209.85.219.46]:46217 "EHLO mail-oa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755550Ab2JKWgr (ORCPT ); Thu, 11 Oct 2012 18:36:47 -0400 MIME-Version: 1.0 In-Reply-To: <1349945859-1350-1-git-send-email-mhocko@suse.cz> References: <20121011085038.GA29295@dhcp22.suse.cz> <1349945859-1350-1-git-send-email-mhocko@suse.cz> From: KOSAKI Motohiro Date: Thu, 11 Oct 2012 18:36:26 -0400 X-Google-Sender-Auth: GU6IXyZ9ty60apwiWM8nTsyA5uc Message-ID: Subject: Re: [PATCH] memcg: oom: fix totalpages calculation for memory.swappiness==0 To: Michal Hocko Cc: Andrew Morton , linux-mm@kvack.org, David Rientjes , KAMEZAWA Hiroyuki , Johannes Weiner , LKML Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1593 Lines: 32 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 -- 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/