linux-kernel - Re: [PATCH 0/5] x86,smp: make ticket spinlock proportional backoff w/ auto tuning

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Date:	Thu, 24 Jan 2013 14:28:41 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Mike Galbraith <bitbucket@...ine.de>
Cc:	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org,
	aquini@...hat.com, walken@...gle.com, eric.dumazet@...il.com,
	lwoodman@...hat.com, jeremy@...p.org,
	Jan Beulich <JBeulich@...ell.com>, knoel@...hat.com,
	chegu_vinod@...com, raghavendra.kt@...ux.vnet.ibm.com,
	mingo@...hat.com
Subject: Re: [PATCH 0/5] x86,smp: make ticket spinlock proportional backoff
 w/ auto tuning


* Mike Galbraith <bitbucket@...ine.de> wrote:

> On Thu, 2013-01-10 at 10:31 -0500, Rik van Riel wrote: 
> > On 01/10/2013 10:19 AM, Mike Galbraith wrote:
> > > On Tue, 2013-01-08 at 17:26 -0500, Rik van Riel wrote:
> > >
> > >> Please let me know if you manage to break this code in any way,
> > >> so I can fix it...
> > >
> > > I didn't break it, but did let it play with rq->lock contention.  Using
> > > cyclictest -Smp99 -i 100 -d 0, with 3 rt tasks for pull_rt_task() to
> > > pull around appears to have been a ~dead heat.
> > 
> > Good to hear that the code seems to be robust. It seems to
> > help prevent performance degradation in some workloads, and
> > nobody seems to have found regressions yet.
> 
> I had hoped for a bit of positive, but a wash isn't surprising 
> given the profile.  I tried tbench too, didn't expect to see 
> anything at all there, and got that.. so both results are 
> positive in that respect.

Ok, that's good.

Rik, mind re-sending the latest series with all the acks and 
Reviewed-by's added?

Thanks,

	Ingo
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