linux-kernel - Re: [patch 1/4] x86: FIFO ticket spinlocks

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Message-ID: <alpine.LFD.0.999.0711020950250.3342@woody.linux-foundation.org>
Date:	Fri, 2 Nov 2007 09:51:27 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Chuck Ebbert <cebbert@...hat.com>
cc:	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...e.de>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [patch 1/4] x86: FIFO ticket spinlocks



On Fri, 2 Nov 2007, Chuck Ebbert wrote:
> 
> There's also a very easy way to get better fairness with our current spinlocks:
> use xchg to release the lock instead of mov.

That does nothing at all.

Yes, it slows the unlock down, which in turn on some machines will make it 
easier for another core/socket to get it, but it's purely about the 
slowdown, nothing else. 

			Linus
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