linux-kernel - Re: [PATCH] sched/fair: Invoke cpufreq hooks for CONFIG

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Date:	Tue, 10 May 2016 10:13:01 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Steve Muckle <steve.muckle@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH] sched/fair: Invoke cpufreq hooks for CONFIG_SMP unset


* Rafael J. Wysocki <rjw@...ysocki.net> wrote:

> On Monday, May 09, 2016 04:53:16 PM Steve Muckle wrote:
> > On Sat, May 07, 2016 at 08:30:51AM +0200, Ingo Molnar wrote:
> > > 
> > > * Peter Zijlstra <peterz@...radead.org> wrote:
> > > 
> > > > On Fri, May 06, 2016 at 02:58:43PM +0200, Rafael J. Wysocki wrote:
> > > > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > > > 
> > > > > Commit 34e2c555f3e1 (cpufreq: Add mechanism for registering utilization
> > > > > update callbacks) overlooked the fact that update_load_avg(), where
> > > > > CFS invokes cpufreq utilization update hooks, becomes an empty stub for
> > > > > CONFIG_SMP unset.  In consequence, if CONFIG_SMP is not set, cpufreq
> > > > > governors are never invoked from CFS and they do not have a chance to
> > > > > evaluate CPU performace levels and update them often enough.  Needless
> > > > > to say, things don't work as expected then.
> > > > > 
> > > > > Fix the problem by making the !CONFIG_SMP stub of update_load_avg()
> > > > > invoke cpufreq update hooks too.
> > > > > 
> > > > > Fixes: 34e2c555f3e1 (cpufreq: Add mechanism for registering utilization update callbacks)
> > > > > Reported-by: Steve Muckle <steve.muckle@...aro.org>
> > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > > 
> > > > Rafael; feel free to push this through the pm tree.
> > > > 
> > > > Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > > 
> > > I already have it in sched/urgent.
> > 
> > Looks like this just missed 4.6-rc7 and the release email for
> > that doesn't suggest an rc8, as it stands...
> 
> But the final 4.6 will be released on Sunday or so and there are a few days left 
> still.

Yeah, I'll send the sched/urgent bits to Linus later today.

Thanks,

	Ingo