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Wed, 17 Jun 2020 16:14:09 -0400 Received: from mail-lj1-x243.google.com (mail-lj1-x243.google.com [IPv6:2a00:1450:4864:20::243]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9A59AC0613EE for ; Wed, 17 Jun 2020 13:14:07 -0700 (PDT) Received: by mail-lj1-x243.google.com with SMTP id c17so4455277lji.11 for ; Wed, 17 Jun 2020 13:14:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=K/gPu7TMycBU2OMmKICnzUSp+xjDAAHE5ZCXBHSedrA=; b=Hgg/nMoOfC6xMGf+J0M+j/XoZSAzvWUNAJO5oRrnxxQZz6Jmm0bdH9VjaHmTQ4XPAi n/s9J0wSZAWbIYX//BzBFy8dbEnTocLEWX0efF+Wc/Hi97+M0oDVNjosY09MY8AutLO8 qpGLDMUievYu4q8rJPW79V9RO2lnQiRDoKZYOwvNwTOtAoz3Y1Yf4CYHpoxy71/O111x XyKu9yBw7Y6GEAQ6DbuX1G6elk8UAN33ZXvp/hMJY42Wbp16m3kGTmL6w9UxFO2mTphj NMM0Gh4+agGODtkiA7pegz8sjaNYzBN5MFM1gmXwuuNuXozNRhBVA/6Ak0mguCvAdC5y uIiA== 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=K/gPu7TMycBU2OMmKICnzUSp+xjDAAHE5ZCXBHSedrA=; b=BtNPnIbCYql7uLEbqsqmCmH7CwZGZC4wzysSYHW2hf3WDGNgbahniAh/ZpMgCWWeC5 AX0Vyr4bdpE8yChSPbCI457jDssQ/i7j002NnlWzfjWcEAT4gEvxNw8ebKfAwMWkbtkZ B2AQcXA8e1Ku3rI4ZcBjdhiah0I0RgJa64kXDfHenGkyWtplp3DkyI7Qlh2vIysQQzHk 18i4rqME9v2a4EtkpVnswk46fyYXWMzmrPTAto/toXHs89fLGAebZTArA5vtOg5kzoTA fPiFs8OHyJV4zBvLrptWBnSxK6kTG8uzfOGNjmsb/UKyIDPC68BYSH/oL3XUJT+rGVuO jZWg== X-Gm-Message-State: AOAM531Ugc7u+kkjL3m+jSnlY3APthut814hY5Oajtrrfk/yJtFk7C6i tg2mLZL9LUqR7ItGlXY/MHQZqGGlUXxIdlA4caSslg== X-Google-Smtp-Source: ABdhPJxu/rE2rptP5d+WfyaHgfX2ttcXAh33IxS8fL6XLG7WEVYacg0tdg5G22BFQHF/I4DoFwlWnsCjNWKyglTnJas= X-Received: by 2002:a2e:974e:: with SMTP id f14mr480197ljj.102.1592424845650; Wed, 17 Jun 2020 13:14:05 -0700 (PDT) MIME-Version: 1.0 References: <20200519084535.GG32497@dhcp22.suse.cz> <20200520190906.GA558281@chrisdown.name> <20200521095515.GK6462@dhcp22.suse.cz> <20200521163450.GV6462@dhcp22.suse.cz> <20200617135758.GA548179@chrisdown.name> <20200617141155.GQ9499@dhcp22.suse.cz> <20200617160624.GS9499@dhcp22.suse.cz> In-Reply-To: <20200617160624.GS9499@dhcp22.suse.cz> From: Naresh Kamboju Date: Thu, 18 Jun 2020 01:43:53 +0530 Message-ID: Subject: Re: mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page To: Michal Hocko , Chris Down Cc: Yafang Shao , Anders Roxell , "Linux F2FS DEV, Mailing List" , linux-ext4 , linux-block , Andrew Morton , open list , Linux-Next Mailing List , linux-mm , Arnd Bergmann , Andreas Dilger , Jaegeuk Kim , "Theodore Ts'o" , Chao Yu , Hugh Dickins , Andrea Arcangeli , Matthew Wilcox , Chao Yu , lkft-triage@lists.linaro.org, Johannes Weiner , Roman Gushchin , Cgroups Content-Type: text/plain; charset="UTF-8" Sender: linux-next-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-next@vger.kernel.org On Wed, 17 Jun 2020 at 21:36, Michal Hocko wrote: > > On Wed 17-06-20 21:23:05, Naresh Kamboju wrote: > > On Wed, 17 Jun 2020 at 19:41, Michal Hocko wrote: > > > > > > [Our emails have crossed] > > > > > > On Wed 17-06-20 14:57:58, Chris Down wrote: > > > > Naresh Kamboju writes: > > > > > mkfs -t ext4 /dev/disk/by-id/ata-TOSHIBA_MG04ACA100N_Y8RQK14KF6XF > > > > > mke2fs 1.43.8 (1-Jan-2018) > > > > > Creating filesystem with 244190646 4k blocks and 61054976 inodes > > > > > Filesystem UUID: 7c380766-0ed8-41ba-a0de-3c08e78f1891 > > > > > Superblock backups stored on blocks: > > > > > 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, > > > > > 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, > > > > > 102400000, 214990848 > > > > > Allocating group tables: 0/7453 done > > > > > Writing inode tables: 0/7453 done > > > > > Creating journal (262144 blocks): [ 51.544525] under min:0 emin:0 > > > > > [ 51.845304] under min:0 emin:0 > > > > > [ 51.848738] under min:0 emin:0 > > > > > [ 51.858147] under min:0 emin:0 > > > > > [ 51.861333] under min:0 emin:0 > > > > > [ 51.862034] under min:0 emin:0 > > > > > [ 51.862442] under min:0 emin:0 > > > > > [ 51.862763] under min:0 emin:0 > > > > > > > > Thanks, this helps a lot. Somehow we're entering mem_cgroup_below_min even > > > > when min/emin is 0 (which should indeed be the case if you haven't set them > > > > in the hierarchy). > > > > > > > > My guess is that page_counter_read(&memcg->memory) is 0, which means > > > > mem_cgroup_below_min will return 1. > > > > > > Yes this is the case because this is likely the root memcg which skips > > > all charges. > > > > > > > However, I don't know for sure why that should then result in the OOM killer > > > > coming along. My guess is that since this memcg has 0 pages to scan anyway, > > > > we enter premature OOM under some conditions. I don't know why we wouldn't > > > > have hit that with the old version of mem_cgroup_protected that returned > > > > MEMCG_PROT_* members, though. > > > > > > Not really. There is likely no other memcg to reclaim from and assuming > > > min limit protection will result in no reclaimable memory and thus the > > > OOM killer. > > > > > > > Can you please try the patch with the `>=` checks in mem_cgroup_below_min > > > > and mem_cgroup_below_low changed to `>`? If that fixes it, then that gives a > > > > strong hint about what's going on here. > > > > > > This would work but I believe an explicit check for the root memcg would > > > be easier to spot the reasoning. > > > > May I request you to send debugging or proposed fix patches here. > > I am happy to do more testing. > > Sure, here is the diff to test. > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index c74a8f2323f1..6b5a31672fbe 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -392,6 +392,13 @@ static inline bool mem_cgroup_below_low(struct mem_cgroup *memcg) > if (mem_cgroup_disabled()) > return false; > > + /* > + * Root memcg doesn't account charges and doesn't support > + * protection > + */ > + if (mem_cgroup_is_root(memcg)) > + return false; > + > return READ_ONCE(memcg->memory.elow) >= > page_counter_read(&memcg->memory); > } > @@ -401,6 +408,13 @@ static inline bool mem_cgroup_below_min(struct mem_cgroup *memcg) > if (mem_cgroup_disabled()) > return false; > > + /* > + * Root memcg doesn't account charges and doesn't support > + * protection > + */ > + if (mem_cgroup_is_root(memcg)) > + return false; > + > return READ_ONCE(memcg->memory.emin) >= > page_counter_read(&memcg->memory); > } After this patch applied the reported issue got fixed. test log link, https://lkft.validation.linaro.org/scheduler/job/1505417#L1429 - Naresh