linux-kernel - Re: [RFC][PATCH 3/7] sched: power: go

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Message-ID: <20131014155555.GN31039@e103034-lin>
Date:	Mon, 14 Oct 2013 16:55:55 +0100
From:	Morten Rasmussen <morten.rasmussen@....com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"mingo@...nel.org" <mingo@...nel.org>,
	"pjt@...gle.com" <pjt@...gle.com>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"rjw@...k.pl" <rjw@...k.pl>,
	"dirk.j.brandewie@...el.com" <dirk.j.brandewie@...el.com>,
	"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
	"alex.shi@...aro.org" <alex.shi@...aro.org>,
	"preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>,
	"efault@....de" <efault@....de>, "corbet@....net" <corbet@....net>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>
Subject: Re: [RFC][PATCH 3/7] sched: power: go_faster/slower power driver
 hints

On Mon, Oct 14, 2013 at 02:48:09PM +0100, Peter Zijlstra wrote:
> On Fri, Oct 11, 2013 at 06:19:13PM +0100, Morten Rasmussen wrote:
> > +static inline void inc_cpu_capacity(int cpu)
> > +{
> > +	if (weighted_cpuload(cpu) > power_of(cpu))
> > +		go_faster(cpu, 0);
> > +}
> > +
> > +static inline void dec_cpu_capacity(int cpu)
> > +{
> > +	if (weighted_cpuload(cpu) < power_of(cpu))
> > +		go_slower(cpu, 0);
> > +}
> 
> It seems wrong to me to use weighted_cpuload() here; that contains the
> task weight, which is irrelevant to power usage. I would expect a pure
> utilization term here.
> 
> Something like:
> 
>   se->avg.runnable_avg_sum / se->avg.runnable_avg_period
> 

Fully agree. There is no unweighted equivalent to cfs.runnable_load_avg
but we could add it. It would be very useful for the power-aware
scheduling. It will add some overhead though.

Morten

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