linux-kernel - Re: [PATCH 0/6] sched,delayacct: Some cleanups

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Date:   Wed, 12 May 2021 13:38:00 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mel Gorman <mgorman@...e.de>
Cc:     Balbir Singh <bsingharora@...il.com>, tglx@...utronix.de,
        mingo@...nel.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, bristot@...hat.com,
        pbonzini@...hat.com, maz@...nel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, riel@...riel.com, hannes@...xchg.org,
        Paul Wise <pabs3@...edaddy.net>
Subject: Re: [PATCH 0/6] sched,delayacct: Some cleanups

On Wed, May 12, 2021 at 12:34:19PM +0100, Mel Gorman wrote:
> > I don't disagree, we've had these around for a while and I know of users
> > that use these stats to find potential starvation. I am OK with default
> > disabled. I suspect distros will have the final say.
> > 
> 
> I think default disabled should be fine. At worst when dealing with a bug
> there would be a need to either reboot or enable at runtime with patch
> 7 included and add that instruction to the bug report when requesting
> iotop data. At worst, a distro could revert the patch if iotop generated
> too many bug reports or patch iotop in the distro package.
> 
> Alternatively, I've added Paul Wise to the cc who is the latest
> committer to iotop.  Maybe he knows who could add/commit a check for
> sysctl.sched_delayacct and if it exists then check if it's 1 and display
> an error suggesting corrective action (add delayacct to the kernel command
> line or sysctl sched.sched_delayacct=1). iotop appears to be in maintenance
> mode but gets occasional commits even if it has not had a new version
> since 2013 so maybe it could get a 0.7 tag if such a check was added.

In the final commit I made the knob be known as task_delayacct. I
figured that was a slightly better name.

But yes, a check in iotop, if that really is the sole user of all this,
would be very nice.

Thanks!