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

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Message-ID: <20200618123743.GA694719@chrisdown.name>
Date:   Thu, 18 Jun 2020 13:37:43 +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:
>On Thu, Jun 18, 2020 at 5:09 AM Chris Down <chris@...isdown.name> wrote:
>>
>> Naresh Kamboju writes:
>> >After this patch applied the reported issue got fixed.
>>
>> Great! Thank you Naresh and Michal for helping to get to the bottom of this :-)
>>
>> I'll send out a new version tomorrow with the fixes applied and both of you
>> credited in the changelog for the detection and fix.
>
>As we have already found that the usage around memory.{emin, elow} has
>many limitations, I think memory.{emin, elow} should be used for
>memcg-tree internally only, that means they can only be used to
>calculate the protection of a memcg in a specified memcg-tree but
>should not be exposed to other MM parts.

I agree that the current semantics are mentally taxing and we should generally 
avoid exposing the implementation details outside of memcg where possible. Do 
you have a suggested rework? :-)