From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Weiner Subject: Re: [RFC PATCH] mm, oom: cgroup-aware OOM-killer Date: Thu, 18 May 2017 14:11:17 -0400 Message-ID: <20170518181117.GA27689@cmpxchg.org> References: <1495124884-28974-1-git-send-email-guro@fb.com> <20170518173002.GC30148@dhcp22.suse.cz> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=cmpxchg.org ; s=x; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject: Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=NBOO9yMTzDqyLU+fF/1wabKBMCxRaqPfUOCj7CCD+ns=; b=zhRsqwV6utEhjeiStqSPN2VU1u hjqlNhganQMCLOo7VTM/lkjuM7RSIR1ykgsldHtKOZOvL7bhZwj09IRZukvx/RTSy/iam2PAkNCIo Pnoo6W2W52XK6zheUcOCir8KfSzrES5752//YckxaP3BqcIySvE3yKZ6LG61D6lVipQc=; Content-Disposition: inline In-Reply-To: <20170518173002.GC30148@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Michal Hocko Cc: Roman Gushchin , Tejun Heo , Li Zefan , Vladimir Davydov , Tetsuo Handa , kernel-team@fb.com, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Thu, May 18, 2017 at 07:30:04PM +0200, Michal Hocko wrote: > On Thu 18-05-17 17:28:04, Roman Gushchin wrote: > > Traditionally, the OOM killer is operating on a process level. > > Under oom conditions, it finds a process with the highest oom score > > and kills it. > > > > This behavior doesn't suit well the system with many running > > containers. There are two main issues: > > > > 1) There is no fairness between containers. A small container with > > a few large processes will be chosen over a large one with huge > > number of small processes. > > > > 2) Containers often do not expect that some random process inside > > will be killed. So, in general, a much safer behavior is > > to kill the whole cgroup. Traditionally, this was implemented > > in userspace, but doing it in the kernel has some advantages, > > especially in a case of a system-wide OOM. > > > > To address these issues, cgroup-aware OOM killer is introduced. > > Under OOM conditions, it looks for a memcg with highest oom score, > > and kills all processes inside. > > > > Memcg oom score is calculated as a size of active and inactive > > anon LRU lists, unevictable LRU list and swap size. > > > > For a cgroup-wide OOM, only cgroups belonging to the subtree of > > the OOMing cgroup are considered. > > While this might make sense for some workloads/setups it is not a > generally acceptable policy IMHO. We have discussed that different OOM > policies might be interesting few years back at LSFMM but there was no > real consensus on how to do that. One possibility was to allow bpf like > mechanisms. Could you explore that path? OOM policy is an orthogonal discussion, though. The OOM killer's job is to pick a memory consumer to kill. Per default the unit of the memory consumer is a process, but cgroups allow grouping processes into compound consumers. Extending the OOM killer to respect the new definition of "consumer" is not a new policy. I don't think it's reasonable to ask the person who's trying to make the OOM killer support group-consumers to design a dynamic OOM policy framework instead. All we want is the OOM policy, whatever it is, applied to cgroups. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org