linux-kernel - Re: [patch v6 10/21] sched: get rq potential maximum utilization

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Date:	Wed, 03 Apr 2013 09:11:50 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Vincent Guittot <vincent.guittot@...aro.org>
CC:	"mingo@...hat.com" <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>, Paul Turner <pjt@...gle.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Mike Galbraith <efault@....de>, gregkh@...uxfoundation.org,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch v6 10/21] sched: get rq potential maximum utilization

On 04/02/2013 10:38 PM, Vincent Guittot wrote:
>> +static unsigned int max_rq_util(int cpu)
>> > +{
>> > +       struct rq *rq = cpu_rq(cpu);
>> > +       unsigned int rt_util = scale_rt_util(cpu);
>> > +       unsigned int cfs_util;
>> > +       unsigned int nr_running;
>> > +
>> > +       cfs_util = (FULL_UTIL - rt_util) > rq->util ? rq->util
>> > +                       : (FULL_UTIL - rt_util);
> rt_util and rq->util don't use the same computation algorithm so the
> results are hardly comparable or addable. In addition, some RT tasks
> can have impacted the rq->util, so they will be accounted in both
> side.

Thanks Vincent!

Yes, rt_util calculated with different way, but it has very similar
meaning with rq->util. So compare them make sense.

Yes, the rq->util and rt_util have some overlap, so we need to remove
the overlap part, otherwise the total utlization of this cpu will beyond
100%. that's not make sense. And since RT task always has higher
priority than cfs task, here I keep the RT utilization and yield the cfs
utilization.
> 
> Vincent
> 


-- 
Thanks Alex
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