From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751890AbdJELqa (ORCPT ); Thu, 5 Oct 2017 07:46:30 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:48602 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751862AbdJELqY (ORCPT ); Thu, 5 Oct 2017 07:46:24 -0400 Date: Thu, 5 Oct 2017 12:45:51 +0100 From: Roman Gushchin To: Michal Hocko CC: Shakeel Butt , Linux MM , Vladimir Davydov , Johannes Weiner , Tetsuo Handa , David Rientjes , Andrew Morton , Tejun Heo , , Cgroups , , LKML Subject: Re: [v10 3/6] mm, oom: cgroup-aware OOM killer Message-ID: <20171005114551.GA6338@castle.dhcp.TheFacebook.com> References: <20171004154638.710-1-guro@fb.com> <20171004154638.710-4-guro@fb.com> <20171004201524.GA4174@castle> <20171005102707.GA12982@castle.dhcp.TheFacebook.com> <20171005111230.i7am3patptvalcat@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; 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There are two things. First, should we do a > > > css_get on the newly selected memcg within the for loop when we still > > > have a reference to it? > > > > We're holding rcu_read_lock, it should be enough. We're bumping css counter > > just before releasing rcu lock. > > yes > > > > > > > Second, for the OFFLINE memcg, you are right oom_evaluate_memcg() will > > > return 0 for offlined memcgs. Maybe no need to call > > > oom_evaluate_memcg() for offlined memcgs. > > > > Sounds like a good optimization, which can be done on top of the current > > patchset. > > You could achive this by checking whether a memcg has tasks rather than > explicitly checking for children memcgs as I've suggested already. Using cgroup_has_tasks() will require additional locking, so I'm not sure it worth it.