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Message-ID: <20090115174440.GF29283@parisc-linux.org>
Date: Thu, 15 Jan 2009 10:44:40 -0700
From: Matthew Wilcox <matthew@....cx>
To: Ingo Molnar <mingo@...e.hu>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Gregory Haskins <ghaskins@...ell.com>,
Andi Kleen <andi@...stfloor.org>,
Chris Mason <chris.mason@...cle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
linux-btrfs <linux-btrfs@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Nick Piggin <npiggin@...e.de>,
Peter Morreale <pmorreale@...ell.com>,
Sven Dietrich <SDietrich@...ell.com>,
Dmitry Adamushko <dmitry.adamushko@...il.com>,
Johannes Weiner <hannes@...xchg.org>
Subject: Re: [GIT PULL] adaptive spinning mutexes
On Wed, Jan 14, 2009 at 08:28:11PM +0100, Ingo Molnar wrote:
> [v2.6.14] [v2.6.29]
>
> Semaphores | Mutexes
> ----------------------------------------------
> | no-spin spin
> |
> [tmpfs] ops/sec: 50713 | 291038 392865 (+34.9%)
> [ext3] ops/sec: 45214 | 283291 435674 (+53.7%)
>
> A 10x macro-performance improvement on ext3, compared to 2.6.14 :-)
>
> While lots of other details got changed meanwhile, i'm sure most of the
> performance win on this particular VFS workload comes from mutexes.
I asked a couple of our benchmarking teams to try -v9. Neither the OLTP
benchmark, nor the kernel-perf test suite found any significant
performance change. I suspect mutex contention isn't a significant
problem for most workloads.
Has anyone found a non-synthetic benchmark where this makes a
significant difference? Aside from btrfs, I mean.
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
--
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