linux-kernel - Re: [patch 2/2] sched: fix select_idle_sibling() logic in select_task_rq

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Date:	Sat, 06 Mar 2010 09:36:45 +0100
From:	Mike Galbraith <efault@....de>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	Arjan van de Ven <arjan@...ux.jf.intel.com>,
	linux-kernel@...r.kernel.org,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Yanmin Zhang <yanmin_zhang@...ux.jf.intel.com>,
	Gautham R Shenoy <ego@...ibm.com>
Subject: Re: [patch 2/2] sched: fix select_idle_sibling() logic in
 select_task_rq_fair()

On Fri, 2010-03-05 at 10:39 -0800, Suresh Siddha wrote:
> plain text document attachment (fix_lat_ctx.patch)
> Performance improvements with this patch:
> "lat_ctx -s 0 2" ~22usec (before-this-patch)	~5usec (after-this-patch)

BTW, is your cpu governor kicking into high gear?  That unpatched number
looks like a throttled down cpu to me.  I know on my box, when there are
micro idles, sometimes cores do not throttle up, making for some fairly
crappy numbers.  Q6600 doesn't throttle down far enough to make such a
_huge_ difference though.

	-Mike

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