linux-kernel - Re: [PATCH 1/1] mutex: prevent optimistic spinning from spinning longer than neccessary (Repost)

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Message-ID: <20100820131920.GC3321@elte.hu>
Date:	Fri, 20 Aug 2010 15:19:20 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	peterz@...radead.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
	Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH  1/1] mutex: prevent optimistic spinning from spinning
 longer than neccessary (Repost)


* Tim Chen <tim.c.chen@...ux.intel.com> wrote:

> > Ingo wrote:
> >
> > These are some rather impressive speedups!
> >
> > Have you tried to see what performance effects this change has on
> smaller
> > boxes? Just to see what flip side (if any) this change has.
> >
> 
> I've done similar experiments with 2.6.35 kernel on smaller boxes.  One is
> on a dual-socket Westmere box (12 cores total, with HT). Another
> experiment is on an old dual-socket Core 2 box (4 cores total, no HT)
> 
> On the 12-core Westmere box, I see a 250% increase for Ingo's mutex-test
> program with my mutex patch but no significant difference in aim7's
> fserver workload.
> 
> On the 4-core Core 2 box, I see the difference with the patch for both
> mutex-test and aim7 fserver are negligible.

Great!

> So far, it seems like the patch has not caused regression on smaller 
> systems.  We'll put it through more workloads to check.

Thanks! The performance results you've posted so far IMO more than justifies 
its inclusion.

	Ingo
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