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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4DE60C433FE for ; Thu, 21 Oct 2021 13:24:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id AEAE36112D for ; Thu, 21 Oct 2021 13:24:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org AEAE36112D Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=virtuozzo.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 1DF066B006C; Thu, 21 Oct 2021 09:24:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 190BE900002; Thu, 21 Oct 2021 09:24:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 07E436B0074; Thu, 21 Oct 2021 09:24:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0093.hostedemail.com [216.40.44.93]) by kanga.kvack.org (Postfix) with ESMTP id EC09C6B006C for ; Thu, 21 Oct 2021 09:24:56 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id A273182499A8 for ; Thu, 21 Oct 2021 13:24:56 +0000 (UTC) X-FDA: 78720514992.05.BF2BFA4 Received: from relay.sw.ru (relay.sw.ru [185.231.240.75]) by imf05.hostedemail.com (Postfix) with ESMTP id D63245084781 for ; Thu, 21 Oct 2021 13:24:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Content-Type:MIME-Version:Date:Message-ID:From: Subject; bh=32AQqOyXATf2il8vKMtcA1KZjbeiQBbBxChRbRVpX1c=; b=U8svhr0WtVyCCoajL MfWY2qnKFAMGWhrFuhh2clnSnUgxIB5VUiueri7BV8w4Lg1vJ95Yve0Nn9RmUgbBApqnosoHWH28a 2Qr/T6ovbjxfCTBgBSxFry+RLyybytywv0xI0sY7I/5ZcGK5VySSkB01Dgcd3CLrOEhy2tt2MdJSw =; Received: from [172.29.1.17] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1mdY3s-006jST-D8; Thu, 21 Oct 2021 16:24:48 +0300 Subject: Re: [PATCH memcg 0/1] false global OOM triggered by memcg-limited task To: Michal Hocko Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Roman Gushchin , Uladzislau Rezki , Vlastimil Babka , Shakeel Butt , Mel Gorman , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel@openvz.org References: <9d10df01-0127-fb40-81c3-cc53c9733c3e@virtuozzo.com> <496ed57e-61c6-023a-05fd-4ef21b0294cf@virtuozzo.com> From: Vasily Averin Message-ID: <31351c6f-af5d-a67d-0bce-d12c8670b313@virtuozzo.com> Date: Thu, 21 Oct 2021 16:24:27 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: D63245084781 Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=virtuozzo.com header.s=relay header.b=U8svhr0W; spf=pass (imf05.hostedemail.com: domain of vvs@virtuozzo.com designates 185.231.240.75 as permitted sender) smtp.mailfrom=vvs@virtuozzo.com; dmarc=pass (policy=quarantine) header.from=virtuozzo.com X-Stat-Signature: 1ba8u5hr8jkkrqza8htn6ckmbreny8bb X-Rspamd-Server: rspam06 X-HE-Tag: 1634822689-329241 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000005, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 21.10.2021 14:49, Michal Hocko wrote: > On Thu 21-10-21 11:03:43, Vasily Averin wrote: >> On 18.10.2021 12:04, Michal Hocko wrote: >>> On Mon 18-10-21 11:13:52, Vasily Averin wrote: >>> [...] >>>> How could this happen? >>>> >>>> User-space task inside the memcg-limited container generated a page fault, >>>> its handler do_user_addr_fault() called handle_mm_fault which could not >>>> allocate the page due to exceeding the memcg limit and returned VM_FAULT_OOM. >>>> Then do_user_addr_fault() called pagefault_out_of_memory() which executed >>>> out_of_memory() without set of memcg. >> >>> I will be honest that I am not really happy about pagefault_out_of_memory. >>> I have tried to remove it in the past. Without much success back then, >>> unfortunately[1]. >>> >>> [1] I do not have msg-id so I cannot provide a lore link but google >>> pointed me to https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1400402.html >> >> I re-read this discussion and in general I support your position. >> As far as I understand your opponents cannot explain why "random kill" is mandatory here, >> they are just afraid that it might be useful here and do not want to remove it completely. > > That aligns with my recollection. > >> Ok, let's allow him to do it. Moreover I'm ready to keep it as default behavior. >> >> However I would like to have some choice in this point. >> >> In general we can: >> - continue to use "random kill" and rely on the wisdom of the ancestors. > > I do not follow. Does that mean to preserve existing oom killer from > #PF? > >> - do nothing, repeat #PF and rely on fate: "nothing bad will happen if we do it again". >> - add some (progressive) killable delay, rely on good will of (unkillable) neighbors and wait for them to release required memory. > > Again, not really sure what you mean > >> - mark the current task as cycled in #PF and somehow use this mark in allocator > > How? > >> - make sure that the current task is really cycled, have no progress, send him fatal signal to kill it and break the cycle. > > No! We cannot really kill the task if we could we would have done it by > the oom killer already > >> - implement any better ideas, >> - use any combination of previous points >> >> We can select required strategy for example via sysctl. > > Absolutely no! How can admin know any better than the kernel? > >> For me "random kill" is worst choice, >> Why can't we just kill the looped process instead? > > See above. > >> It can be marked as oom-unkillable, so OOM-killer was unable to select it. >> However I doubt it means "never kill it", for me it is something like "last possible victim" priority. > > It means never kill it because of OOM. If it is retrying because of OOM > then it is effectively the same thing. > > The oom killer from the #PF doesn't really provide any clear advantage > these days AFAIK. On the other hand it allows for a very disruptive > behavior. In a worst case it can lead to a system panic if the > VM_FAULT_OOM is not really caused by a memory shortage but rather a > wrong error handling. If a task is looping there without any progress > then it is still kilallable which is a much saner behavior IMHO. Let's continue this discussion in "Re: [PATCH memcg 3/3] memcg: handle memcg oom failures" thread. .