From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9673C7EE29 for ; Mon, 22 May 2023 13:03:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234175AbjEVND4 (ORCPT ); Mon, 22 May 2023 09:03:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33124 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231495AbjEVNDy (ORCPT ); Mon, 22 May 2023 09:03:54 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4CBE795; Mon, 22 May 2023 06:03:52 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id EE5231FEFD; Mon, 22 May 2023 13:03:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1684760630; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DrtDbupRjXTYRj2tZ8j8I/X6g23GzYeO+ha6ND6W5ms=; b=suVckYdzUWeSehtbUYtrY8aIrry6qsyz9sDDBEHs1h3Eua4XcbY3irusmUqS2No/hcQeaS ek/Vzt88mLX32eaY6tLLxK52XXBMgBFktKrdb06SvcVK6PRDeIeb2Y7AB96DlM1FXN66jC hJivbKMhHDfz7qqloyaIPFKnuABQ2C0= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id BE0E813776; Mon, 22 May 2023 13:03:50 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id Ci3tLTZoa2RRbQAAMHmgww (envelope-from ); Mon, 22 May 2023 13:03:50 +0000 Date: Mon, 22 May 2023 15:03:50 +0200 From: Michal Hocko To: =?utf-8?B?56iL5Z6y5rab?= Chengkaitao Cheng Cc: "tj@kernel.org" , "lizefan.x@bytedance.com" , "hannes@cmpxchg.org" , "corbet@lwn.net" , "roman.gushchin@linux.dev" , "shakeelb@google.com" , "akpm@linux-foundation.org" , "brauner@kernel.org" , "muchun.song@linux.dev" , "viro@zeniv.linux.org.uk" , "zhengqi.arch@bytedance.com" , "ebiederm@xmission.com" , "Liam.Howlett@oracle.com" , "chengzhihao1@huawei.com" , "pilgrimtao@gmail.com" , "haolee.swjtu@gmail.com" , "yuzhao@google.com" , "willy@infradead.org" , "vasily.averin@linux.dev" , "vbabka@suse.cz" , "surenb@google.com" , "sfr@canb.auug.org.au" , "mcgrof@kernel.org" , "feng.tang@intel.com" , "cgroups@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" Subject: Re: [PATCH v3 0/2] memcontrol: support cgroup level OOM protection Message-ID: References: <900EF82B-9899-46DD-9ACC-16D82D9B7A3F@didiglobal.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <900EF82B-9899-46DD-9ACC-16D82D9B7A3F@didiglobal.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Sorry for a late reply but I was mostly offline last 2 weeks] On Tue 09-05-23 06:50:59, 程垲涛 Chengkaitao Cheng wrote: > At 2023-05-08 22:18:18, "Michal Hocko" wrote: [...] > >Your cover letter mentions that then "all processes in the cgroup as a > >whole". That to me reads as oom.group oom killer policy. But a brief > >look into the patch suggests you are still looking at specific tasks and > >this has been a concern in the previous version of the patch because > >memcg accounting and per-process accounting are detached. > > I think the memcg accounting may be more reasonable, as its memory > statistics are more comprehensive, similar to active page cache, which > also increases the probability of OOM-kill. In the new patch, all the > shared memory will also consume the oom_protect quota of the memcg, > and the process's oom_protect quota of the memcg will decrease. I am sorry but I do not follow. Could you elaborate please? Are you arguing for per memcg or per process metrics? [...] > >> In the final discussion of patch v2, we discussed that although the adjustment range > >> of oom_score_adj is [-1000,1000], but essentially it only allows two usecases > >> (OOM_SCORE_ADJ_MIN, OOM_SCORE_ADJ_MAX) reliably. Everything in between is > >> clumsy at best. In order to solve this problem in the new patch, I introduced a new > >> indicator oom_kill_inherit, which counts the number of times the local and child > >> cgroups have been selected by the OOM killer of the ancestor cgroup. By observing > >> the proportion of oom_kill_inherit in the parent cgroup, I can effectively adjust the > >> value of oom_protect to achieve the best. > > > >What does the best mean in this context? > > I have created a new indicator oom_kill_inherit that maintains a negative correlation > with memory.oom.protect, so we have a ruler to measure the optimal value of > memory.oom.protect. An example might help here. > >> about the semantics of non-leaf memcgs protection, > >> If a non-leaf memcg's oom_protect quota is set, its leaf memcg will proportionally > >> calculate the new effective oom_protect quota based on non-leaf memcg's quota. > > > >So the non-leaf memcg is never used as a target? What if the workload is > >distributed over several sub-groups? Our current oom.group > >implementation traverses the tree to find a common ancestor in the oom > >domain with the oom.group. > > If the oom_protect quota of the parent non-leaf memcg is less than the sum of > sub-groups oom_protect quota, the oom_protect quota of each sub-group will > be proportionally reduced > If the oom_protect quota of the parent non-leaf memcg is greater than the sum > of sub-groups oom_protect quota, the oom_protect quota of each sub-group > will be proportionally increased > The purpose of doing so is that users can set oom_protect quota according to > their own needs, and the system management process can set appropriate > oom_protect quota on the parent non-leaf memcg as the final cover, so that > the system management process can indirectly manage all user processes. I guess that you are trying to say that the oom protection has a standard hierarchical behavior. And that is fine, well, in fact it is mandatory for any control knob to have a sane hierarchical properties. But that doesn't address my above question. Let me try again. When is a non-leaf memcg potentially selected as the oom victim? It doesn't have any tasks directly but it might be a suitable target to kill a multi memcg based workload (e.g. a full container). > >All that being said and with the usecase described more specifically. I > >can see that memcg based oom victim selection makes some sense. That > >menas that it is always a memcg selected and all tasks withing killed. > >Memcg based protection can be used to evaluate which memcg to choose and > >the overall scheme should be still manageable. It would indeed resemble > >memory protection for the regular reclaim. > > > >One thing that is still not really clear to me is to how group vs. > >non-group ooms could be handled gracefully. Right now we can handle that > >because the oom selection is still process based but with the protection > >this will become more problematic as explained previously. Essentially > >we would need to enforce the oom selection to be memcg based for all > >memcgs. Maybe a mount knob? What do you think? > > There is a function in the patch to determine whether the oom_protect > mechanism is enabled. All memory.oom.protect nodes default to 0, so the function > returns 0 by default. How can an admin determine what is the current oom detection logic? -- Michal Hocko SUSE Labs