linux-kernel - Re: [PATCH 09/10] x86-32: use SSE for atomic64

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Message-ID: <4B7D86BC.10000@zytor.com>
Date:	Thu, 18 Feb 2010 10:28:12 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Luca Barbieri <luca@...a-barbieri.com>
CC:	Andi Kleen <andi@...stfloor.org>, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/10] x86-32: use SSE for atomic64_read/set if available

On 02/18/2010 10:14 AM, Luca Barbieri wrote:
> 
>> I really feel that without a *strong* use case for this, there is
>> absolutely no point.
> For the specific 32-bit atomic64_t case, it is an improvement, but not
> necessarily significant in the big picture.
> Being able to efficiently use SSE in the kernel might however be more
> broadly useful.
> memcpy/memset/etc. (assuming SSE is the best option for these at least
> on some processors) and checksums come to mind.
> Also non-temporal SSE moves might be useful for things like memory
> compaction without clobbering caches.

We already do that kind of stuff, using
kernel_fpu_begin()..kernel_fpu_end().  We went through some pain a bit
ago to clean up "private hacks" that complicated things substantially.

	-hpa
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