linux-kernel - Re: [patch 0/7] sched: change nohz idle load balancing logic to push model

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Date:	Thu, 20 May 2010 21:35:47 +1000
From:	Nigel Cunningham <ncunningham@...a.org.au>
To:	Dominik Brodowski <linux@...inikbrodowski.net>,
	Nigel Cunningham <nigel@...onice.net>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arjan van de Ven <arjan@...ux.jf.intel.com>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	ego@...ibm.com, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch 0/7] sched: change nohz idle load balancing logic to	push
 model

Hi.

On 20/05/10 21:17, Dominik Brodowski wrote:
> Hey,
>
> On Thu, May 20, 2010 at 09:07:42PM +1000, Nigel Cunningham wrote:
>> "Load balancing tick" is still number one in my powertop list of top
>> causes of wakeups (sitting at ~60 to 80 per second as I type this, with
>> ~170 wakeups per second total). Comparing this to the numbers I posted
>> earlier, we seem to have a win.
>>
>> I do wonder, though, whether further work could still be done. If I take
>> one core offline, for example, I'm still getting load balancing ticks.
>> Intuitively, I'd expect there to be no need for them with only one core
>> available. But maybe I'm just ignorant of what's going on.
>
> Are you using HZ=1000, and is the CPU active ~ 6-8 % ? If so, is it just the
> regular timer tick while the CPU is active, and so not a real "wakeup"? (Or
> possibly double the number if both CPUs are active)

HZ is 1000, and the CPU running percentage in Powertop is low (2% when 
I'm not typing).

Regards,

Nigel
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