linux-kernel - Re: [rfc 00/45] [RFC] CPU ops and a rework of per cpu data handling on x86

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Message-Id: <200711200425.34849.ak@suse.de>
Date:	Tue, 20 Nov 2007 04:25:34 +0100
From:	Andi Kleen <ak@...e.de>
To:	David Miller <davem@...emloft.net>
Cc:	clameter@....com, akpm@...ux-foundation.org, travis@....com,
	mathieu.desnoyers@...ymtl.ca, linux-kernel@...r.kernel.org
Subject: Re: [rfc 00/45] [RFC] CPU ops and a rework of per cpu data handling on x86_64


> Although we have a per-cpu area base in a fixed global register
> for addressing, the above isn't beneficial on sparc64 because
> the atomic is much slower than doing a:
>
> 	local_irq_disable();
> 	nonatomic_percpu_memory_op();
> 	local_irq_enable();

Again might be pointing out the obvious, but you 
need of course save_flags()/restore_flags(), not disable/enable().

If it was just disable/enable x86 could do it much faster too 
and Christoph probably would never felt the need to approach
this project for his SLUB fast path.

-Andi
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