linux-kernel - Re: [patch 00/28] Add cmpxchg64_local and cmpxchg

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Message-ID: <20070827201941.GA5653@Krystal>
Date:	Mon, 27 Aug 2007 16:19:41 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Christoph Lameter <clameter@....com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 00/28] Add cmpxchg64_local and cmpxchg_local to each architecture

* Christoph Lameter (clameter@....com) wrote:
> On Mon, 27 Aug 2007, Mathieu Desnoyers wrote:
> 
> > Here is the patch series for 2.6.23-rc3-mm1 that adds cmpxchg_local, and now
> > also cmpxchg64_local, to each architecture.
> 
> Any planned uses of cmpxchg64_local? 

Let's say it could possibly eliminate the xtime read seqlock on x86
(should be investigated) and can be useful to overcome the
non-synchronized TSC handling when taking TSC-based timestamps. All
these operations require locking to play with 64 bits values on 32 bits
architectures, which could be improved by cmpxchg64_local.

But again, it would require some testing to see if we can improve
performances there.

Mathieu

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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