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

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Date:	Sat, 7 May 2016 08:13:10 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	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>,
	Steve Muckle <steve.muckle@...aro.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] sched/fair: Invoke cpufreq hooks for CONFIG_SMP unset

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>