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Date: Wed, 30 Mar 2011 18:07:56 +0200
From: Tejun Heo <tj@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <andi@firstfloor.org>, Ingo Molnar <mingo@elte.hu>,
        Thomas Gleixner <tglx@linutronix.de>, x86@kernel.org,
        Christoph Lameter <cl@linux.com>, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Pekka Enberg <penberg@kernel.org>
Subject: Re: [PATCH tip:x86/mm 1/3] x86: A fast way to check capabilities
 of the current cpu
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 <m2k4g1zdmt.fsf@firstfloor.org>
 <4D93531F.5080403@zytor.com>
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Hello,

On Wed, Mar 30, 2011 at 08:58:23AM -0700, H. Peter Anvin wrote:
> >> Add this_cpu_has() which determines if the current cpu has a certain
> >> ability using a segment prefix and a bit test operation.
> > 
> > 
> > Hmm: if the CPU capability is really tested in a performance critical
> > path, wouldn't it even be better to just use static_branch() now? 
> > 
> 
> We have static_cpu_has() for this specific purpose (it actually predates
> static_branch()).

These patches have performance benefits but I don't think it would be
noticeable.  I think it's more of code cleanup.

Thanks.

-- 
tejun
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