linux-kernel - Re: [git pull] core/percpu for v2.6.27

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Date:	Tue, 15 Jul 2008 08:46:57 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Travis <travis@....com>
Subject: Re: [git pull] core/percpu for v2.6.27

Linus Torvalds wrote:
> Can you explain what this does and who needs it? The percpu_xchg() looks 
> particularly pointless, since it's always a locked SMP-safe instruction on 
> x86, so a nonpreemptible load+store will likely be much faster.

The essence of those changes is to work towards unifying the i386 and 
x86-64 percpu mechanisms.  But I wasn't terribly convinced by some of 
the frills around the edges, like the xchg operation.  The work is being 
driven by Mike Travis and the huge numa people, so perhaps they have a 
use for it.

    J

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