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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 E30AEC433E2 for ; Tue, 1 Sep 2020 15:32:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8FC362166E for ; Tue, 1 Sep 2020 15:32:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="EHuuu2pz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8FC362166E 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 1465990000C; Tue, 1 Sep 2020 11:32:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0F35B900002; Tue, 1 Sep 2020 11:32:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F254A90000C; Tue, 1 Sep 2020 11:32:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0217.hostedemail.com [216.40.44.217]) by kanga.kvack.org (Postfix) with ESMTP id DCFD3900002 for ; Tue, 1 Sep 2020 11:32:48 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 6BB50362E for ; Tue, 1 Sep 2020 15:32:48 +0000 (UTC) X-FDA: 77214885216.06.quill16_0316f8927099 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id 3838B100349BF for ; Tue, 1 Sep 2020 15:32:48 +0000 (UTC) X-HE-Tag: quill16_0316f8927099 X-Filterd-Recvd-Size: 6125 Received: from mail-ej1-f65.google.com (mail-ej1-f65.google.com [209.85.218.65]) by imf27.hostedemail.com (Postfix) with ESMTP for ; Tue, 1 Sep 2020 15:32:47 +0000 (UTC) Received: by mail-ej1-f65.google.com with SMTP id q13so2259625ejo.9 for ; Tue, 01 Sep 2020 08:32:47 -0700 (PDT) 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=4y5+uILsrYEyrll+p0CQ1799yDtGVcYn/QLXWN/UkVA=; b=EHuuu2pzBr1VfUBw4YoRiSfvSUiZeM+77kGjAP5zTLHasH7nR9vXXYvwCrbZU6c2jd 4seupK2oQl7hy/pRNHsPIqGejkRNxOtFMlnhfBZDpAiMkHr5pZB6BzPT4m+xJPonISe1 HNL48Aq235dCBlPMhV8inHNlZDOIrbnOh1JBXPfbeG8+sj6XuyqKsj94Gpd9ONs14vLu deSYvLYAn6bVnvmYKfnhfxtYq2kvw0toScDDKCc1SxRZHd8XQ+4rc2te9/bh4pe/QeAl lQCzapBnm6XmP/Hk7wQ5e2G3zy3d5GlwxxTvtVvi1NsTwVz1Ra28amh4VKBfVkpE2OfS 5CZw== 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=4y5+uILsrYEyrll+p0CQ1799yDtGVcYn/QLXWN/UkVA=; b=VK6Pyvprm282fB2fQxwv6OzodfHaJ5I8s4M73ZqKvgMu1ePJi9GlbmRIM6zYhFRmyU PS/v+4eJqCwoR+nD2YgzdrAi2dxAOPr2bnmSg9nYZDEyBY/z75byrEOVjQLz8l6G18qi 2bFm+iNiAa5JyCTHTsT1xm7AExNmq4zZvuDUYOEsQLFRO7QYwPfrrn+woMsqgAOE7Bq6 2QdlQl1BI2/8VnH4a0vppUz/3T0/YhG9oog3ckRMimk69gBp3Rgi7PKvA29kX5q9pCRr gw5JHP/90gXGmUkJ+nSnHpmF69XUhC9KLIJ6Fdo6w2UBvT8s4IIGaOzxhKRJPH+8jOQU idJA== X-Gm-Message-State: AOAM531hr7Im+cnq95BCJQEnd2oIDPNoMY11YXOYcUiLqR3F006w9mVM AhwWFCijrirLrBpTtPUbueQBThG2hwwh0uIh35o= X-Google-Smtp-Source: ABdhPJzjka1igjLabnL5+FLiBQxxm/UurFtkX4pyV20hzOcltWvHAgjxNxAU2zE5rwt6/lT63IqZjcdxApMAe3KOB6I= X-Received: by 2002:a17:906:3a85:: with SMTP id y5mr1900924ejd.507.1598974366460; Tue, 01 Sep 2020 08:32:46 -0700 (PDT) MIME-Version: 1.0 References: <20190812222911.2364802-1-guro@fb.com> <20190812222911.2364802-2-guro@fb.com> <20190813142752.35807b6070db795674f86feb@linux-foundation.org> <20190813214643.GA20632@tower.DHCP.thefacebook.com> In-Reply-To: <20190813214643.GA20632@tower.DHCP.thefacebook.com> From: Yang Shi Date: Tue, 1 Sep 2020 08:32:33 -0700 Message-ID: Subject: Re: [PATCH 1/2] mm: memcontrol: flush percpu vmstats before releasing memcg To: Roman Gushchin Cc: Andrew Morton , "linux-mm@kvack.org" , Michal Hocko , Johannes Weiner , "linux-kernel@vger.kernel.org" , Kernel Team , "stable@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 3838B100349BF X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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: This report is kind of late, hope everyone still remembers the context. I just happened to see a similar problem on our v4.19 kernel, please see the below output from memory.stat: total_cache 7361626112 total_rss 8268165120 total_rss_huge 0 total_shmem 0 total_mapped_file 4154929152 total_dirty 389689344 total_writeback 101376000 ... [snip] ... total_inactive_anon 4096 total_active_anon 1638400 total_inactive_file 208990208 total_active_file 275030016 And memory.usage_in_bytes: 1248215040 The total_* counters are way bigger than the counters of LRUs and usage. Some ephemeral cgroups were created/deleted frequently under this problematic cgroup. And this host has been up for more than 200 days. I didn't see such problems on shorter uptime hosts (the other 4.19 host is up for 19 days) and v5.4 hosts. v4.19 also updates stats from per-cpu caches, and total_* sum all sub cgroups together. So it seems this is the same problem. Anyway this is not a significant problem since we can get the correct numbers from other counters, i.e. LRUs, but just confusing. Not sure if it is worth backporting the fix to v4.19. On Tue, Aug 13, 2019 at 2:46 PM Roman Gushchin wrote: > > On Tue, Aug 13, 2019 at 02:27:52PM -0700, Andrew Morton wrote: > > On Mon, 12 Aug 2019 15:29:10 -0700 Roman Gushchin wrote: > > > > > Percpu caching of local vmstats with the conditional propagation > > > by the cgroup tree leads to an accumulation of errors on non-leaf > > > levels. > > > > > > Let's imagine two nested memory cgroups A and A/B. Say, a process > > > belonging to A/B allocates 100 pagecache pages on the CPU 0. > > > The percpu cache will spill 3 times, so that 32*3=96 pages will be > > > accounted to A/B and A atomic vmstat counters, 4 pages will remain > > > in the percpu cache. > > > > > > Imagine A/B is nearby memory.max, so that every following allocation > > > triggers a direct reclaim on the local CPU. Say, each such attempt > > > will free 16 pages on a new cpu. That means every percpu cache will > > > have -16 pages, except the first one, which will have 4 - 16 = -12. > > > A/B and A atomic counters will not be touched at all. > > > > > > Now a user removes A/B. All percpu caches are freed and corresponding > > > vmstat numbers are forgotten. A has 96 pages more than expected. > > > > > > As memory cgroups are created and destroyed, errors do accumulate. > > > Even 1-2 pages differences can accumulate into large numbers. > > > > > > To fix this issue let's accumulate and propagate percpu vmstat > > > values before releasing the memory cgroup. At this point these > > > numbers are stable and cannot be changed. > > > > > > Since on cpu hotplug we do flush percpu vmstats anyway, we can > > > iterate only over online cpus. > > > > > > Fixes: 42a300353577 ("mm: memcontrol: fix recursive statistics correctness & scalabilty") > > > > Is this not serious enough for a cc:stable? > > I hope the "Fixes" tag will work, but yeah, my bad, cc:stable is definitely > a good idea here. > > Added stable@ to cc. > > Thanks! >