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Re: [PATCH 3/3 v5] cpufreq: governor: Replace timers with utilization update callbacks

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  Re: [PATCH 3/3 v5] cpufreq: governor: Replace timers with  utilization update callbacks Gautham R Shenoy <ego@linux.vnet.ibm.com> - 2016-02-09 11:10 +0100
    Re: [PATCH 3/3 v5] cpufreq: governor: Replace timers with utilization  update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-09 19:50 +0100

#1330018 — Re: [PATCH 3/3 v5] cpufreq: governor: Replace timers with utilization update callbacks

Hello Rafael,

On Sun, Feb 07, 2016 at 03:50:31PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> Instead of using a per-CPU deferrable timer for queuing up governor
> work items, register a utilization update callback that will be
> invoked from the scheduler on utilization changes.
> 
> The sampling rate is still the same as what was used for the
> deferrable timers and the added irq_work overhead should be offset by
> the eliminated timers overhead, so in theory the functional impact of
> this patch should not be significant.

I tested this patch series (including v5 of PATCH 3) on POWER with
Viresh's CPUFreq test suite. I didn't see any issues with the
patchset except for a lockdep splat involving "s_active" and
"od_dbs_cdata.mutex", which was also observed on 4.5-rc3 and which
was fixed by Viresh's recent patches. 

With a kernbench run, there were no regression when compared to 4.5-rc3.

FWIW, Tested-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>

> 
> Thanks,
> Rafael

--
Thanks and Regards
gautham.

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#1330581 — Re: [PATCH 3/3 v5] cpufreq: governor: Replace timers with utilization update callbacks

On Tue, Feb 9, 2016 at 11:01 AM, Gautham R Shenoy
<ego@linux.vnet.ibm.com> wrote:
> Hello Rafael,
>
> On Sun, Feb 07, 2016 at 03:50:31PM +0100, Rafael J. Wysocki wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>
>> Instead of using a per-CPU deferrable timer for queuing up governor
>> work items, register a utilization update callback that will be
>> invoked from the scheduler on utilization changes.
>>
>> The sampling rate is still the same as what was used for the
>> deferrable timers and the added irq_work overhead should be offset by
>> the eliminated timers overhead, so in theory the functional impact of
>> this patch should not be significant.
>
> I tested this patch series (including v5 of PATCH 3) on POWER with
> Viresh's CPUFreq test suite. I didn't see any issues with the
> patchset except for a lockdep splat involving "s_active" and
> "od_dbs_cdata.mutex", which was also observed on 4.5-rc3 and which
> was fixed by Viresh's recent patches.
>
> With a kernbench run, there were no regression when compared to 4.5-rc3.
>
> FWIW, Tested-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>

Thank you!

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