linux-kernel - Re: [patches] [PATCH] [8/35] x86_64: a memcpy that tries to reducecache pressure

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Date:	Mon, 30 Apr 2007 08:26:05 +0100
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	"Bryan O'Sullivan" <bos@...hscale.com>, "Andi Kleen" <ak@...e.de>
Cc:	"Roland Dreier" <rolandd@...co.com>,
	<linux-kernel@...r.kernel.org>, <patches@...-64.org>
Subject: Re: [patches] [PATCH] [8/35] x86_64: a memcpy that tries to
	reducecache pressure

>+	testb	$8, %dxl	/* rdx is 3,5,6,7,9..15 */

Could you use the more conventional name %dl (or whatever is being meant)
here?

>+.L42:
>+	prefetchnta	128(%rsi)

I think I commented similarly on a previous version of the patch: This will 
- result in still bringing the first 128 bytes into the cache
- prevent caching of memory beyond the buffer being dealt with

>+	sfence

Similarly, I continue to believe this is wrong here (again I commented before
that this is likely unnecessary, or if at all, it should be an lfence).

>+	orl	%edx, %edx

Operations of this type generally should use 'test', not 'or' or 'and'.

Jan


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