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

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Date:	Thu, 10 Jan 2013 20:30:13 +0100
From:	Mike Galbraith <bitbucket@...ine.de>
To:	Rik van Riel <riel@...hat.com>
Cc:	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

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.

-Mike

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