linux-kernel - Re: [PATCH V2] idle/intel_powerclamp: Redesign idle injection to use bandwidth control mechanism

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Date:	Fri, 13 Feb 2015 06:03:38 -0800
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
CC:	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	jacob.jun.pan@...el.com, fweisbec@...il.com, frederic@...nel.org,
	daniel.lezcano@...aro.org, amit.kucheria@...aro.org,
	edubezval@...il.com, viresh.kumar@...aro.org, rui.zhang@...el.com
Subject: Re: [PATCH V2] idle/intel_powerclamp: Redesign idle injection to
 use bandwidth control mechanism


> Also, exposing these and root_task_group is of course vile. Not to
> mention you change the user (cgroup) interface without mention.
>
> In any case, I cannot see how this could ever work. Bandwidth is shared
> across CPUs; nothing will even attempt to get CPUs to idle at the same
> time.

idle injection is only worth it if you can get package C states,
e.g. all cpus in the system are idle at the same time.

(and in powerclamp, the package C state %age is the target of the control
loop, since that's pretty much the amount of power reduced)

>
>

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