Re: [PATCH] cpufreq: schedutil: govern how frequently we change frequency with rate_limit
From: Rafael J. Wysocki
Date: Mon Feb 20 2017 - 08:54:27 EST
On Monday, February 20, 2017 03:28:03 PM Viresh Kumar wrote:
> On 17-02-17, 13:48, Peter Zijlstra wrote:
> > On Fri, Feb 17, 2017 at 01:15:56PM +0100, Rafael J. Wysocki wrote:
> > > On Thursday, February 16, 2017 01:36:05 PM Peter Zijlstra wrote:
> > > > On Thu, Feb 16, 2017 at 03:42:10PM +0530, Viresh Kumar wrote:
> > > > > But when I discussed this with Vincent, he suggested that it may not be required
> > > > > at all as the scheduler (with the helped of "decayed") doesn't call into
> > > > > schedutil too often, i.e. at least 1 ms. And if the CPUs are stable enough (i.e.
> > > > > no interruptions to the running task), we wouldn't reevaluate before the next
> > > > > tick.
> > > >
> > > > There are still the attach/detach callers to cfs_rq_util_change() that
> > > > kick in for fork/exit and migration.
> > > >
> > > > But yes, barring those we shouldn't end up calling it at silly rates.
> > >
> > > OK
> > >
> > > Does this mean that running governor computations every time its callback
> > > is invoked by the scheduler would be fine?
> > I'd say yes right up till the point someone reports a regression ;-)
> @Rafael: Do you want me to send a V2 with the changes you suggested in
> commit log?
Yes, in general, but I have more suggestions regarding that. :-)
I'll send them shortly.