From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH] memcg: force charge kmem counter too Date: Mon, 28 May 2018 11:11:10 +0200 Message-ID: <20180528091110.GG1517@dhcp22.suse.cz> References: <20180525185501.82098-1-shakeelb@google.com> <20180526185144.xvh7ejlyelzvqwdb@esperanza> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Shakeel Butt Cc: Vladimir Davydov , Andrew Morton , Greg Thelen , Johannes Weiner , Linux MM , Cgroups , LKML On Sat 26-05-18 15:37:05, Shakeel Butt wrote: > On Sat, May 26, 2018 at 11:51 AM, Vladimir Davydov > wrote: > > On Fri, May 25, 2018 at 11:55:01AM -0700, Shakeel Butt wrote: > >> Based on several conditions the kernel can decide to force charge an > >> allocation for a memcg i.e. overcharge memcg->memory and memcg->memsw > >> counters. Do the same for memcg->kmem counter too. In cgroup-v1, this > >> bug can cause a __GFP_NOFAIL kmem allocation fail if an explicit limit > >> on kmem counter is set and reached. > > > > memory.kmem.limit is broken and unlikely to ever be fixed as this knob > > was deprecated in cgroup-v2. The fact that hitting the limit doesn't > > trigger reclaim can result in unexpected behavior from user's pov, like > > getting ENOMEM while listing a directory. Bypassing the limit for NOFAIL > > allocations isn't going to fix those problem. > > I understand that fixing NOFAIL will not fix all other issues but it > still is better than current situation. IMHO we should keep fixing > kmem bit by bit. > > One crazy idea is to just break it completely by force charging all the time. What is the limit good for then? Accounting? -- Michal Hocko SUSE Labs