linux-kernel - RE: regression caused by bb6ab52f2bef ("intel_pstate: Do not set utilization update hook too early")

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Date:	Fri, 17 Jun 2016 16:09:33 +0000
From:	Jisheng Zhang <jszhang@...vell.com>
To:	"Rafael J. Wysocki" <rafael@...nel.org>
CC:	Peter Zijlstra <peterz@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"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 bb6ab52f2bef ("intel_pstate: Do not set
 utilization update hook too early")

Dear all,

If using acpi-cpufreq instead, v4.6, v4.6-rc3, v4.7-rc3 can't reproduce the issue. It seems
only intel_pstate is impacted.

Thanks,
Jisheng
________________________________________
From: Jisheng Zhang
Sent: Friday, June 17, 2016 23:53
To: Rafael J. Wysocki
Cc: Peter Zijlstra; Paul E. McKenney; Rafael J. Wysocki; Viresh Kumar; linux-pm@...r.kernel.org; Linux Kernel Mailing List
Subject: RE: regression caused by bb6ab52f2bef ("intel_pstate: Do not set utilization update hook too early")

Dear Rafael,

I used intel_pstate.

I just tested v4.7-rc3, which should include commit 4578ee7e1def intel_pstate: Avoid
unnecessary synchronize_sched() during initialization, I can still get the same
wakeups, so it's not sufficient.

Another clue maybe helpful, I found these top2 wakeup/s is consistent, e.g
rcu_sched always gives about 10 wakeups/s, and tick_sched_timer gave
5.6-5.9 wakeups/s,

            144.3 µs/s      10.0        Process        [rcu_sched]

            193.9 µs/s       5.7        Timer          tick_sched_timer

Thanks,
Jisheng

________________________________________
From:  Rafael J. Wysocki
Sent: Friday, June 17, 2016 23:42
To: Jisheng Zhang
Cc: Peter Zijlstra; Paul E. McKenney; Rafael J. Wysocki; Viresh Kumar; linux-pm@...r.kernel.org; Linux Kernel Mailing List
Subject: Re: regression caused by bb6ab52f2bef ("intel_pstate: Do not set utilization update hook too early")

On Fri, Jun 17, 2016 at 5:40 PM, Rafael J. Wysocki  wrote:
> On Fri, Jun 17, 2016 at 5:32 PM, Jisheng Zhang  wrote:
>> Hi all,
>>
>> First of all, sorry for top post, only webmail is available now.
>>
>> Second, sorry again for report incorrect commit, I were too tired this morning so I remember the wrong commit.  The regression is caused by bb6ab52f2bef ("intel_pstate: Do not set utilization update hook too early"), so I update the email title.
>
> OK, that makes much more sense. :-)
>
> And
>
> 4578ee7e1def intel_pstate: Avoid unnecessary synchronize_sched()
> during initialization
>
> is not sufficient I suppose?

I mean, it is not sufficient to reduce the number of wakeups again?