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Date: Thu, 29 Oct 2020 17:56:12 +0000 From: Valentin Schneider <valentin.schneider@....com> To: Peter Zijlstra <peterz@...radead.org> Cc: tglx@...utronix.de, mingo@...nel.org, linux-kernel@...r.kernel.org, bigeasy@...utronix.de, 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 17/19] sched: Add migrate_disable() tracepoints On 29/10/20 17:43, Peter Zijlstra wrote: > On Thu, Oct 29, 2020 at 04:27:26PM +0000, Valentin Schneider wrote: >> Don't you want those directly after the ->migration_disabled write? >> esp. for migrate_enable(), if that preempt_enable() leads to a context >> switch then the disable->enable deltas won't reflect the kernel view. >> >> That delta may indeed include the time it took to run the stopper and >> fix the task's affinity on migrate_enable(), but it could include all >> sorts of other higher-priority tasks. > > I can put them in the preempt_disable() section I suppose, but these > tracers should be looking at task_sched_runtime(), not walltime, and > then the preemption doesn't matter. > True. I was thinking of how to process it downstream, and the first thing that came to mind was that rd->overutilized flag which we do monitor fairly closely; however that is system-wide while migrate_disable() is task-specific. > Also, a distinct lack of actual users atm.. :/ If you'd rather ditch this one altogether until someone asks for it, that also works for me.
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