linux-kernel - Re: [PATCH v4 11/19] sched/core: Make migrate disable and CPU hotplug cooperative

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Message-ID: <f82cfe32b6f7c43c83da1552776de8aed6947840.camel@redhat.com>
Date:   Wed, 02 Dec 2020 16:59:56 -0500
From:   Qian Cai <qcai@...hat.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Valentin Schneider <valentin.schneider@....com>,
        Peter Zijlstra <peterz@...radead.org>, tglx@...utronix.de,
        mingo@...nel.org, linux-kernel@...r.kernel.org,
        qais.yousef@....com, swood@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vincent.donnefort@....com, tj@...nel.org,
        ouwen210@...mail.com
Subject: Re: [PATCH v4 11/19] sched/core: Make migrate disable and CPU
 hotplug cooperative

On Mon, 2020-11-23 at 19:13 +0100, Sebastian Andrzej Siewior wrote:
> On 2020-11-18 09:44:34 [-0500], Qian Cai wrote:
> > On Tue, 2020-11-17 at 19:28 +0000, Valentin Schneider wrote:
> > > We did have some breakage in that area, but all the holes I was aware of
> > > have been plugged. What would help here is to see which tasks are still
> > > queued on that outgoing CPU, and their recent activity.
> > > 
> > > Something like
> > > - ftrace_dump_on_oops on your kernel cmdline
> > > - trace-cmd start -e 'sched:*'
> > >  <start the test here>
> > > 
> > > ought to do it. Then you can paste the (tail of the) ftrace dump.
> > > 
> > > I also had this laying around, which may or may not be of some help:
> > 
> > Once I have found a reliable reproducer, I'll report back.
> 
> any update?

Just back from a vacation. I have been running the same workload on today's
linux-next for a few hours and it has been good so far. I'll surely report back
if it happens again in our daily runs.