linux-kernel - Re: [PATCH -v8][RFC] mutex: implement adaptive spinning

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Message-ID: <alpine.LFD.2.00.0901120818070.6528@localhost.localdomain>
Date:	Mon, 12 Jan 2009 08:20:34 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Ingo Molnar <mingo@...e.hu>,
	"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>
Subject: Re: [PATCH -v8][RFC] mutex: implement adaptive spinning

On Mon, 12 Jan 2009, Linus Torvalds wrote:
> 
> You made it back into the locked version.

Btw, even if you probably had some reason for this, one thing to note is 
that I think Chris' performance testing showed that the version using a 
lock was inferior to his local btrfs hack, while the unlocked version 
actually beat his hack.

Maybe I misunderstood his numbers, though. But if I followed that sub-part 
of the test right, it really means that the locked version is pointless - 
it will never be able to replace peoples local hacks for this same thing, 
because it just doesn't give the performance people are looking for.

Since the whole (and _only_) point of this thing is to perform well, 
that's a big deal.

		Linus
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