linux-kernel - Re: [GIT PULL] adaptive spinning mutexes

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Message-ID: <20090114184746.GA21334@elte.hu>
Date:	Wed, 14 Jan 2009 19:47:46 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Gregory Haskins <ghaskins@...ell.com>,
	Matthew Wilcox <matthew@....cx>,
	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


* Ingo Molnar <mingo@...e.hu> wrote:

> Linus,
> 
> Please pull the adaptive-mutexes-for-linus git tree from:
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git adaptive-mutexes-for-linus
> 
> We dropped two fresh patches from v11 for the time being: the two debug 
> patches, they had test failures [they triggered mutex debugging false 
> positives].
> 
> So this tree is v10 (which got a lot of testing already) plus Chris's 
> performance patch. It passes all x86 runtime tests here.

Latest performance figures, on a 2-socket 16-way Nehalem test-system, 
running the code above, measured via "test-mutex V 128 10" VFS 
creat+unlink scalability test on tmpfs and ext3:

                              no-spin           spin

 [tmpfs]    avg ops/sec:       291038         392865       (+34.9%)
 [ext3]     avg ops/sec:       283291         435674       (+53.7%)

Those numbers impress the heck out of me, rarely do we have such kind of 
speedups these days, for any established functionality.

We still have the /sys/debug/sched_features tunable under 
CONFIG_SCHED_DEBUG=y, so should this cause any performance regressions 
somewhere, it can be pinned down and blamed back on this change easily, 
without bisection and without rebooting the box.

	Ingo
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