linux-kernel - Re: [PATCH] cpuidle: menu: use nr_running instead of cpuload for calculating perf mult

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Message-ID: <4FCCB4DD.4060407@linux.intel.com>
Date:	Mon, 04 Jun 2012 06:15:09 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Vladimir Davydov <vdavydov@...allels.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Len Brown <lenb@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpuidle: menu: use nr_running instead of cpuload for
 calculating perf mult

On 6/4/2012 3:24 AM, Vladimir Davydov wrote:
> rq->cpuload strongly depends on cgroup hierarchy. For example, if hundreds of
> tasks are running inside cpu:/test cgroup, the sum of cpuload over all cpus
> won't exceed 1024 (by default). That makes the cpuidle menu governor take wrong
> decisions, which can negatively affect overall performance.

nr_running is the wrong answer... it is instantaneous, not longer term.
cpuidle wants a longer term, per cpu, notion of "busy", to use as proxy
for performance sensitivity.


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