linux-ext4 - Re: mm: mkfs.ext4 invoked oom-killer on i386

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Date:   Fri, 29 May 2020 02:56:44 +0100
From:   Chris Down <chris@...isdown.name>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        Michal Hocko <mhocko@...nel.org>,
        Anders Roxell <anders.roxell@...aro.org>,
        "Linux F2FS DEV, Mailing List" 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        linux-ext4 <linux-ext4@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, Arnd Bergmann <arnd@...db.de>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Theodore Ts'o <tytso@....edu>, Chao Yu <chao@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Chao Yu <yuchao0@...wei.com>, lkft-triage@...ts.linaro.org,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, Cgroups <cgroups@...r.kernel.org>
Subject: Re: mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page

Yafang Shao writes:
>Look at this patch[1] carefully you will find that it introduces the
>same issue that I tried to fix in another patch [2]. Even more sad is
>these two patches are in the same patchset. Although this issue isn't
>related with the issue found by Naresh, we have to ask ourselves why
>we always make the same mistake ?
>One possible answer is that we always forget the lifecyle of
>memory.emin before we read it. memory.emin doesn't have the same
>lifecycle with the memcg, while it really has the same lifecyle with
>the reclaimer. IOW, once a reclaimer begins the protetion value should
>be set to 0, and after we traversal the memcg tree we calculate a
>protection value for this reclaimer, finnaly it disapears after the
>reclaimer stops. That is why I highly suggest to add an new protection
>member in scan_control before.

I agree with you that the e{min,low} lifecycle is confusing for everyone -- the 
only thing I've not seen confirmation of is any confirmed correlation with the 
i386 oom killer issue. If you've validated that, I'd like to see the data :-)