linux-kernel - Re: sched: Avoid SMT siblings in select_idle

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Message-ID: <20120223161709.GA26810@elte.hu>
Date:	Thu, 23 Feb 2012 17:17:09 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
Cc:	Mike Galbraith <efault@....de>,
	Peter Zijlstra <peterz@...radead.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Paul Turner <pjt@...gle.com>
Subject: Re: sched: Avoid SMT siblings in select_idle_sibling() if possible


* Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com> wrote:

> * Ingo Molnar <mingo@...e.hu> [2012-02-23 12:26:50]:
> 
> > pro perf tip of the day: did you know that it's possible to run:
> > 
> >   perf stat --repeat 10 --null perf bench sched pipe
> 
> Ah yes ..had forgotten that! What is the recommended # of 
> iterations to run?

Well, I start at 3 or 5 and sometimes increase it to get a 
meaningful stddev - i.e. one that is smaller than half of the 
measured effect. (for cases where I expect an improvement and 
want to measure it.)

Thanks,

	Ingo
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