linux-kernel - Re: [REGRESSION] 5-10% increase in IO latencies with nohz balance patch

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Message-ID: <87lf0y9i8x.mognet@arm.com>
Date:   Mon, 06 Dec 2021 09:48:14 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Josef Bacik <josef@...icpanda.com>
Cc:     peterz@...radead.org, vincent.guittot@...aro.org,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-btrfs@...r.kernel.org
Subject: Re: [REGRESSION] 5-10% increase in IO latencies with nohz balance patch

On 03/12/21 14:00, Josef Bacik wrote:
> On Fri, Dec 03, 2021 at 12:03:27PM +0000, Valentin Schneider wrote:
>> Could you give the 4 top patches, i.e. those above
>> 8c92606ab810 ("sched/cpuacct: Make user/system times in cpuacct.stat more precise")
>> a try?
>>
>> https://git.gitlab.arm.com/linux-arm/linux-vs.git -b mainline/sched/nohz-next-update-regression
>>
>> I gave that a quick test on the platform that caused me to write the patch
>> you bisected and looks like it didn't break the original fix. If the above
>> counter-measures aren't sufficient, I'll have to go poke at your
>> reproducers...
>>
>
> It's better but still around 6% regression.  If I compare these patches to the
> average of the last few days worth of runs you're 5% better than before, so
> progress but not completely erased.
>

Hmph, time for me to reproduce this locally then. Thanks!