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 X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81A94C432C0 for ; Sat, 23 Nov 2019 05:53:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 403E920672 for ; Sat, 23 Nov 2019 05:53:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WI14ncch" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 403E920672 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C77C36B0544; Sat, 23 Nov 2019 00:53:35 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C28136B0545; Sat, 23 Nov 2019 00:53:35 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B16966B0546; Sat, 23 Nov 2019 00:53:35 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0032.hostedemail.com [216.40.44.32]) by kanga.kvack.org (Postfix) with ESMTP id 970586B0544 for ; Sat, 23 Nov 2019 00:53:35 -0500 (EST) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 3F05E181AEF32 for ; Sat, 23 Nov 2019 05:53:35 +0000 (UTC) X-FDA: 76186475190.12.hen87_3c5da101fbb0e X-HE-Tag: hen87_3c5da101fbb0e X-Filterd-Recvd-Size: 6726 Received: from mail-il1-f195.google.com (mail-il1-f195.google.com [209.85.166.195]) by imf21.hostedemail.com (Postfix) with ESMTP for ; Sat, 23 Nov 2019 05:53:34 +0000 (UTC) Received: by mail-il1-f195.google.com with SMTP id a7so9387435ild.6 for ; Fri, 22 Nov 2019 21:53:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=HxuKpYaXm1Mn5TZjdIFQEW8vnA5RGR/pZ4ZZt38A3fA=; b=WI14ncch4/k41ihRULddSZ7YbjoYpQ1mdPgJrKUZYAKnNU77BlENsbcUFj1hpy3ipp SpjAp1YuKhQKaQO7/M5UfIXW+0dzdsAFYzyldMbAva6VW4rJoTNcpwaPNxKRo/E3WECi x4jij88JMGagGHpmzuwgPh/+tpNc351BiyfCEktrnk/uF0Np/wIz+5yCKSiUFCEqVprv bvNkUgHi2y6yP1lYl2iIQrN5ulfLok4HGN/ncKWUzA/usn6EaZLolxZmZNtadPea7sin ciW0fWyykMTUevv7o0iv8+qcJEMeVFP0Rl/qCEK7/JApj0jJw3twaK15My44FgGrhHUI pfPg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=HxuKpYaXm1Mn5TZjdIFQEW8vnA5RGR/pZ4ZZt38A3fA=; b=a67zQn6c6kFDAxuBHP/oVEsnGoCEh/bIxEjrslsKeFYUpjBrI3fmjfPfTVXSDfNQOP Sn2b0YqJF5uFWYM22LdO2Cy/slWL5tUua22k5vU/crE6QQNkMk37WvoLwx0iX66wnMcu LNhenaNfxOHaFQSdunvw80mtw1Q8Mwj3wqZh+PU5q+DAOm84MqVro2mDoS1zC/7uxtaI azgR90N9gXkzQASd6t8wiam655pLdg9gc/SFC7MDp4i/HSLVmzS9v753TKnsn4dqk/qV XrtxtoZyksToWx+AIgmS+xIAMbFOWEBW65ulb8IFNagDCCxx7Z/v/OOFRxVIPD/tsv78 0KpQ== X-Gm-Message-State: APjAAAVXBffdPY1N7qXq7fN1Q5Tn84m+u/KgFhoAktJQ9A2UgLOWX8u9 Iyk3Ph3S99QALRUOKLxP+5uBZXd57ZWrN+GVzOg= X-Google-Smtp-Source: APXvYqytN2F3FSBJs2L/c+beSWtC7ZPTWuZHs1L1ejT4NV+2gjfykjNlc+m9QP5Nc6Htcg2XRar3h7iuYMtulEvx2Wk= X-Received: by 2002:a92:aac9:: with SMTP id p70mr894495ill.168.1574488414032; Fri, 22 Nov 2019 21:53:34 -0800 (PST) MIME-Version: 1.0 References: <1574239985-1916-1-git-send-email-laoar.shao@gmail.com> <20191120102157.GF23213@dhcp22.suse.cz> <20191120114043.GH23213@dhcp22.suse.cz> <20191122102842.GR23213@dhcp22.suse.cz> In-Reply-To: <20191122102842.GR23213@dhcp22.suse.cz> From: Yafang Shao Date: Sat, 23 Nov 2019 13:52:57 +0800 Message-ID: Subject: Re: [PATCH] mm, memcg: show memcg min setting in oom messages To: Michal Hocko Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Linux MM Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Nov 22, 2019 at 6:28 PM Michal Hocko wrote: > > On Wed 20-11-19 20:23:54, Yafang Shao wrote: > > On Wed, Nov 20, 2019 at 7:40 PM Michal Hocko wrote: > > > > > > On Wed 20-11-19 18:53:44, Yafang Shao wrote: > > > > On Wed, Nov 20, 2019 at 6:22 PM Michal Hocko wrote: > > > > > > > > > > On Wed 20-11-19 03:53:05, Yafang Shao wrote: > > > > > > A task running in a memcg may OOM because of the memory.min settings of his > > > > > > slibing and parent. If this happens, the current oom messages can't show > > > > > > why file page cache can't be reclaimed. > > > > > > > > > > min limit is not the only way to protect memory from being reclaim. The > > > > > memory might be pinned or unreclaimable for other reasons (e.g. swap > > > > > quota exceeded for memcg). > > > > > > > > Both swap or unreclaimabed (unevicteable) is printed in OOM messages. > > > > > > Not really. Consider a memcg which has reached it's swap limit. The > > > anonymous memory is not really reclaimable even when there is a lot of > > > swap space available. > > > > > > > The memcg swap limit is already printed in oom messages, see bellow, > > > > [ 141.721625] memory: usage 1228800kB, limit 1228800kB, failcnt 18337 > > [ 141.721958] swap: usage 0kB, limit 9007199254740988kB, failcnt 0 > > But you do not have any insight on the swap limit down the oom > hierarchy, do you? > > > > > Why not just print the memcgs which are under memory.min protection or > > > > something like a total number of min protected memory ? > > > > > > Yes, this would likely help. But the main question really reamains, is > > > this really worth it? > > > > > > > If it doesn't cost too much, I think it is worth to do it. > > As the oom path is not the critical path, so adding some print info > > should not add much overhead. > > Generating a lot of output for the oom reports has been a real problem > in many deployments. So why not only print non-zero counters ? If some counters are 0, we don't print them, that can reduce the oom reports. Something like "isolated_file:0 unevictable:0 dirty:0 writeback:0 unstable:0" can all be removed, and we consider them as zero by default. I mean we can optimze the OOM reports and only print the useful information to make it not be a problem in many deployments. > [...] > > > > I have said in the commit log, that we don't know why the file cache > > > > can't be reclaimed (when evictable is 0 and dirty is 0 as well.) > > > > > > And the counter argument is that this will not help you there much in > > > many large and much more common cases. > > > > > > I argue, and I might be wrong here so feel free to correct me, that the > > > reclaim protection guarantee (min) is something to be under admins > > > control. It shouldn't really happen nilly-willy because it has really > > > large consequences, the OOM including. So if there is a suspicious > > > amount of memory that could be reclaimed normally then the reclaim > > > protection is really the first suspect to go after. > > > -- > > > > I don't know whether it happens nilly-willy or not. > > It is a reclaim protection guarantee (so essentially an mlock like > thing) so it better have to be properly considered when used. > > > But if we all know that it may cause OOMs and it don't take too much > > effort to show it in the OOM messages, > > I do not think we are in agreement here. As mentioned above the oom > report is quite heavy already. So it should be other way around. There > should be a strong reason to add something more. A real use case where > not having that information is making debugging ooms considerably much > harder. > > -- > Michal Hocko > SUSE Labs