From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752948AbcB2S32 (ORCPT ); Mon, 29 Feb 2016 13:29:28 -0500 Received: from mail-wm0-f42.google.com ([74.125.82.42]:34369 "EHLO mail-wm0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751053AbcB2S30 (ORCPT ); Mon, 29 Feb 2016 13:29:26 -0500 Date: Mon, 29 Feb 2016 19:29:23 +0100 From: Michal Hocko To: Vladimir Davydov Cc: Andrew Morton , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: memcontrol: reset memory.low on css offline Message-ID: <20160229182923.GR16930@dhcp22.suse.cz> References: <1456766193-16255-1-git-send-email-vdavydov@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1456766193-16255-1-git-send-email-vdavydov@virtuozzo.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 29-02-16 20:16:33, Vladimir Davydov wrote: > When a cgroup directory is removed, the memory cgroup subsys state does > not disappear immediately. Instead, it's left hanging around until the > last reference to it is gone, which implies reclaiming all pages from > its lruvec. > > In the unified hierarchy, there's the memory.low knob, which can be used > to set a best-effort protection for a memory cgroup - the reclaimer > first scans those cgroups whose consumption is above memory.low, and > only if it fails to reclaim enough pages, it gets to the rest. > > Currently this protection is not reset when the cgroup directory is > removed. As a result, if a dead memory cgroup has a lot of page cache > charged to it and a high value of memory.low, it will result in higher > pressure exerted on live cgroups, and userspace will have no ways to > detect such consumers and reconfigure memory.low properly. > > To fix this, let's reset memory.low on css offline. Makes sense to me > Signed-off-by: Vladimir Davydov Acked-by: Michal Hocko > --- > mm/memcontrol.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index ae8b81c55685..ab7bfe870c7d 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4214,6 +4214,8 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css) > > memcg_offline_kmem(memcg); > wb_memcg_offline(memcg); > + > + memcg->low = 0; > } > > static void mem_cgroup_css_released(struct cgroup_subsys_state *css) > -- > 2.1.4 -- Michal Hocko SUSE Labs