linux-kernel - Re: [this_cpu_xx V7 0/8] Per cpu atomics in core allocators and cleanup

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Date:	Thu, 17 Dec 2009 14:43:33 -0600 (CST)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
cc:	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	Mel Gorman <mel@....ul.ie>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [this_cpu_xx V7 0/8] Per cpu atomics in core allocators and
 cleanup

On Thu, 17 Dec 2009, Mathieu Desnoyers wrote:

> Some quick test on my Intel Xeon E5405:
>
> local cmpxchg:  14 cycles
> xchg:           18 cycles
>
> So yes, indeed, the non-LOCK prefixed local cmpxchg seems a bit faster
> than the xchg, given the latter has an implied LOCK prefix.
>
> Code used for local cmpxchg:
>                 old = var;
>                 do {
>                         ret = cmpxchg_local(&var, old, 4);
>                         if (likely(ret == old))
>                                 break;
>                         old = ret;
>                 } while (1);
>

Great. Could you also put that into "patch-format"?

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