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

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Message-Id: <1268114749.6349.20.camel@marge.simson.net>
Date:	Tue, 09 Mar 2010 07:05:49 +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" <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 Mon, 2010-03-08 at 14:24 -0800, Suresh Siddha wrote:
> On Fri, 2010-03-05 at 12:25 -0800, Mike Galbraith wrote:
> > 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)
> > 
> > Hm.  On my Q6600 box, it's nowhere near that.
> 
> My numbers are based on an atom netbook.

Wish I had an atom to play with, hard to even imagine 22 usec lat_ctx,
that's some _serious_ pain.

> > Calling the waking cpu idle in that case is a mistake.  Just because the
> > sync hint was used does not mean there is no gain to be had. 
> 
> Ok. I dropped that part in v2 patches that I just posted.

Yeah, I see mails (ramble ramble) crossed in the night.  I'll take them
out for a spin, see if your box can get fixed up without busting mine :)

	-Mike

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