linux-kernel - Re: [PATCH v10 1/3] cpufreq: Add mechanism for registering utilization update callbacks

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Date:	Wed, 9 Mar 2016 14:22:58 +0100
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Juri Lelli <juri.lelli@....com>,
	Steve Muckle <steve.muckle@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v10 1/3] cpufreq: Add mechanism for registering
 utilization update callbacks

On Wed, Mar 9, 2016 at 1:35 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, Feb 15, 2016 at 10:47:22PM +0100, Rafael J. Wysocki wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>
>> Introduce a mechanism by which parts of the cpufreq subsystem
>> ("setpolicy" drivers or the core) can register callbacks to be
>> executed from cpufreq_update_util() which is invoked by the
>> scheduler's update_load_avg() on CPU utilization changes.
>>
>> This allows the "setpolicy" drivers to dispense with their timers
>> and do all of the computations they need and frequency/voltage
>> adjustments in the update_load_avg() code path, among other things.
>>
>> The update_load_avg() changes were suggested by Peter Zijlstra.
>>
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
>> ---
>>  drivers/cpufreq/cpufreq.c |   45 +++++++++++++++++++++++++++++++++++++++++++++
>>  include/linux/cpufreq.h   |   34 ++++++++++++++++++++++++++++++++++
>>  kernel/sched/deadline.c   |    4 ++++
>>  kernel/sched/fair.c       |   26 +++++++++++++++++++++++++-
>>  kernel/sched/rt.c         |    4 ++++
>>  kernel/sched/sched.h      |    1 +
>>  6 files changed, 113 insertions(+), 1 deletion(-)
>>
>
> So with the understanding that we'll work on getting rid of
> cpufreq_trigger_update().

That definitely is the plan.

> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Thanks! :-)

> Also, Vincent had some concerns about the exact placement of the
> callback, and I see no problem in moving it if there's need.

Yup, same here.