linux-kernel - Re: [PATCH V6] powercap/drivers/idle_injection: Add an idle injection framework

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Message-ID: <0b72e862-6bbe-e706-79f8-e1b690982920@linaro.org>
Date:   Wed, 13 Jun 2018 22:00:39 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     "Pandruvada, Srinivas" <srinivas.pandruvada@...el.com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Zhang, Rui" <rui.zhang@...el.com>,
        "edubezval@...il.com" <edubezval@...il.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "andrea.parri@...rulasolutions.com" 
        <andrea.parri@...rulasolutions.com>,
        "kevin.wangtao@...aro.org" <kevin.wangtao@...aro.org>,
        "leo.yan@...aro.org" <leo.yan@...aro.org>,
        "daniel.thompson@...aro.org" <daniel.thompson@...aro.org>,
        "javi.merino@...nel.org" <javi.merino@...nel.org>,
        "vincent.guittot@...aro.org" <vincent.guittot@...aro.org>
Subject: Re: [PATCH V6] powercap/drivers/idle_injection: Add an idle injection
 framework

On 13/06/2018 17:54, Pandruvada, Srinivas wrote:
> On Tue, 2018-06-12 at 14:00 +0200, Daniel Lezcano wrote:
>> Initially, the cpu_cooling device for ARM was changed by adding a new
>> policy inserting idle cycles. The intel_powerclamp driver does a
>> similar action.
>>
>> Instead of implementing idle injections privately in the cpu_cooling
>> device, move the idle injection code in a dedicated framework and
>> give
>> the opportunity to other frameworks to make use of it.
>>
>> The framework relies on the smpboot kthreads which handles via its
>> main loop the common code for hotplugging and [un]parking.
>>
>> This code was previously tested with the cpu cooling device and went
>> through several iterations. It results now in split code and API
>> exported in the header file. It was tested with the cpu cooling
>> device
>> with success.
>>
> May be I have missed, but I don't see any use of powercap sysfs.
> 
> We created powercap sys that user space is presented a common interface
> for power capping. The RAPL driver was also submitted as cooling device
> before, but suggestion was to create this powercap.
> 
> So if powercap interface is not enough then may be we should enhance
> that.

We are creating a framework for idle injection. This framework can then
be used by the cpu_cooling device, the power_clamp and in addition a
power capping for ARM (if it makes sense).



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