linux-kernel - Re: regression caused by 08f511fd41c3 ("cpufreq: Reduce cpufreq_update

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Message-ID: <CAJZ5v0hd9HKUHzEnnBnp4-DmcHXgy1GgMK-st=Bs36rxzYR5xw@mail.gmail.com>
Date:	Fri, 17 Jun 2016 15:09:36 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Jisheng Zhang <jszhang@...vell.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: regression caused by 08f511fd41c3 ("cpufreq: Reduce
 cpufreq_update_util() overhead a bit")

On Fri, Jun 17, 2016 at 10:40 AM, Jisheng Zhang <jszhang@...vell.com> wrote:
> Dear all,
>
> On Fri, 17 Jun 2016 16:30:23 +0800 Jisheng Zhang wrote:
>
>> Dear all,
>>
>> I found one regression: In an idle system, wakeups/s (reported by powertop)
>> is increased a lot, e.g on a intel snb 4 core platform, the wakeup event
>> number is increased from 8 wakeups/s to 24 wakeup/s. bisect points to
>> this commit. I could send detailed bisect log if it's wanted.
>>
>
> more information maybe useful: after the commit, the top two wakeup source
> are
>
>         Process        [rcu_sched]
>
>         Timer          tick_sched_timer

And what was there before the commit?

Granted, I'm not seeing this on my systems.

Paul, Peter, any ideas about what may be going on here?

Thanks,
Rafael