Re: [PATCH] x86: PM: Register syscore_ops for scale invariance

[Peter Zijlstra]

On Tue, Jan 19, 2021 at 04:12:20PM +0100, Rafael J. Wysocki wrote:
> On Tue, Jan 12, 2021 at 4:10 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> >
> > On Tue, Jan 12, 2021 at 4:02 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > >
> > > On Fri, Jan 08, 2021 at 07:05:59PM +0100, Rafael J. Wysocki wrote:
> > > > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > > >
> > > > On x86 scale invariace tends to be disabled during resume from
> > > > suspend-to-RAM, because the MPERF or APERF MSR values are not as
> > > > expected then due to updates taking place after the platform
> > > > firmware has been invoked to complete the suspend transition.
> > > >
> > > > That, of course, is not desirable, especially if the schedutil
> > > > scaling governor is in use, because the lack of scale invariance
> > > > causes it to be less reliable.
> > > >
> > > > To counter that effect, modify init_freq_invariance() to register
> > > > a syscore_ops object for scale invariance with the ->resume callback
> > > > pointing to init_counter_refs() which will run on the CPU starting
> > > > the resume transition (the other CPUs will be taken care of the
> > > > "online" operations taking place later).
> > > >
> > > > Fixes: e2b0d619b400 ("x86, sched: check for counters overflow in frequency invariant accounting")
> > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > >
> > > Thanks!, I'll take it through the sched/urgent tree?
> >
> > That works, thanks!
> 
> Any news on this front?  It's been a few days ...

My bad, it's been held up behind me trying to fix another sched
regression. Lemme push out just this one so it doesn't go walk-about.