linux-kernel - Re: [patches] [PATCH 2.6.21 review I] [21/25] x86_64: a memcpy that tries to reduce cache pressure

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Message-Id: <200702121125.28867.ak@suse.de>
Date:	Mon, 12 Feb 2007 11:25:28 +0100
From:	Andi Kleen <ak@...e.de>
To:	"Jan Beulich" <jbeulich@...ell.com>
Cc:	"Bryan O'Sullivan" <bos@...hscale.com>,
	"Roland Dreier" <rolandd@...co.com>, linux-kernel@...r.kernel.org,
	patches@...-64.org
Subject: Re: [patches] [PATCH 2.6.21 review I] [21/25] x86_64: a memcpy that tries to reduce cache pressure


> This looks a little strange to me:
> - the first 128 bytes are still going through the cache
> - up to 192 bytes past the copied area are being marked non-temporal, while
>   there's nothing known about that area

Yes that seems quite bogus.

> - sfence seems questionable here, I would have thought this should be lfence,
>   or perhaps even none at all

Agreed -- it's not needed.

I think i also objected earlier to the jump table which is likely slower.

Will drop for now.

-Andi
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