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

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Message-ID: <4FCC92EC.2000808@parallels.com>
Date:	Mon, 4 Jun 2012 14:50:20 +0400
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Ingo Molnar <mingo@...e.hu>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Len Brown <lenb@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpuidle: menu: use nr_running instead of cpuload for
 calculating perf mult

On 06/04/2012 02:32 PM, Peter Zijlstra wrote:
> On Mon, 2012-06-04 at 14:24 +0400, 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.
>>
>> To cope this, use nr_running last seen in __update_cpu_load() instead of
>> cpuload for calculating performance multiplier.
> What is cpuidle trying to do?

Basing on cpuload, it selects idle state. The less the load, the lowest 
the state.
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