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

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Date:	Thu, 19 Aug 2010 15:24:46 -0700 (PDT)
From:	"Tim Chen" <tim.c.chen@...ux.intel.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Tim Chen" <tim.c.chen@...ux.intel.com>,
	"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)

> 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.

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

Tim

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