linux-kernel - Re: [PATCH] cgroup: Fix rootcg cpu.stat guest double counting

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Message-ID: <161a70b7-ee6f-bbc7-8a2e-1fd42fcba3eb@yandex-team.com>
Date:   Mon, 15 Nov 2021 19:41:12 +0300
From:   Andrey Ryabinin <arbn@...dex-team.com>
To:     Daniel Jordan <daniel.m.jordan@...cle.com>,
        Dan Schatzberg <schatzberg.dan@...il.com>
Cc:     Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Boris Burkov <boris@....io>,
        "open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] cgroup: Fix rootcg cpu.stat guest double counting



On 10/29/21 8:21 PM, Daniel Jordan wrote:
> On Thu, Oct 28, 2021 at 03:15:27PM -0700, Dan Schatzberg wrote:
>> In account_guest_time in kernel/sched/cputime.c guest time is
>> attributed to both CPUTIME_NICE and CPUTIME_USER in addition to
>> CPUTIME_GUEST_NICE and CPUTIME_GUEST respectively. Therefore, adding
>> both to calculate usage results in double counting any guest time at
>> the rootcg.
> 
> Yes, definitely a bug.  The same fix was posted a couple months ago as
> part of a series but never picked up:
> 
>   https://x-lore.kernel.org/all/20210820094005.20596-3-arbn@yandex-team.com/
> 
> The series also touched cputime, so we might be waiting for scheduler
> folks?   +Ingo +Peter +Andrey
> 

Yeah, I'll do rebase and send v3