linux-kernel - Re: [PATCH 2/4] nohz: Synchronize sleep time stats with seqlock

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Date:	Tue, 20 Aug 2013 08:41:58 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Fernando Luis Vázquez Cao 
	<fernando_b1@....ntt.co.jp>, Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/4] nohz: Synchronize sleep time stats with seqlock

On 8/20/2013 8:35 AM, Frederic Weisbecker wrote:
> On Tue, Aug 20, 2013 at 08:33:50AM -0700, Arjan van de Ven wrote:
>> On 8/20/2013 8:29 AM, Frederic Weisbecker wrote:
>>
>>>>
>>>> Of course, if we can get away with completely removing all of that
>>>> (which I think Arjan suggested was a real possibility) then that would
>>>> be ever so much better still :-)
>>>
>>> Would be lovely. But I don't know much about cpufreq, I hope somebody who's
>>> familiar with that code can handle this. Then once there are no more users
>>> of get_cpu_iowait_sleep_time() I can simply zap and clean the tick/time related
>>> code.
>>
>> it's just doing the "idle = 100 - busy% - iowait%" calculation.
>> (with the later part only for Intel cpus iirc)
>>
>> in a perfect world the scheduler would be doing that calculation in the first place ;-)
>>
>> removing the later part will impact performance some on specific workloads,
>> but most Intel cpus that this applies to should not be using cpufreq anymore
>> anyway.
>
> Are there other users than intel?
>

http://lxr.linux.no/linux+v3.10.7/drivers/cpufreq/cpufreq_ondemand.c#L69

nope
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