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

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Message-ID: <20100520111753.GA2264@isilmar-3.linta.de>
Date:	Thu, 20 May 2010 13:17:53 +0200
From:	Dominik Brodowski <linux@...inikbrodowski.net>
To:	Nigel Cunningham <nigel@...onice.net>
Cc:	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>,
	Nigel Cunningham <ncunningham@...a.org.au>
Subject: Re: [patch 0/7] sched: change nohz idle load balancing logic to
	push model

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)

Best,
	Dominik
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