From: Dave Jones <davej@codemonkey.org.uk>
To: Matthew Wilcox <willy@debian.org>
Cc: Linus Torvalds <torvalds@transmeta.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Add generic prefetch xor routines
Date: Thu, 17 Oct 2002 18:27:29 +0100 [thread overview]
Message-ID: <20021017172729.GA29177@suse.de> (raw)
In-Reply-To: <20021017180134.X15163@parcelfarce.linux.theplanet.co.uk>
On Thu, Oct 17, 2002 at 06:01:34PM +0100, Matthew Wilcox wrote:
>
> Both PA-RISC and IA64 benefit from these generic prefetching routines.
> Maybe other CPUs will too.
>
> + do {
> + prefetchw(p1+8);
> + prefetch(p2+8);
> + p1[0] ^= p2[0];
> + p1[1] ^= p2[1];
> + p1[2] ^= p2[2];
> + p1[3] ^= p2[3];
> + p1[4] ^= p2[4];
> + p1[5] ^= p2[5];
> + p1[6] ^= p2[6];
> + p1[7] ^= p2[7];
> + p1 += 8;
> + p2 += 8;
> + } while (--lines > 0);
Won't this prefetch past the end of the buffer ?
Some CPUs have problems with prefetching non-existant areas
of RAM iirc. (Which is why the memcpy routines do a prefetching
loop, and then a non prefetching loop to copy the tail).
Dave
--
| Dave Jones. http://www.codemonkey.org.uk
next prev parent reply other threads:[~2002-10-17 17:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-17 17:01 [PATCH] Add generic prefetch xor routines Matthew Wilcox
2002-10-17 17:27 ` Dave Jones [this message]
2002-10-21 14:08 ` Alan Cox
2002-10-21 14:21 ` Matthew Wilcox
2002-10-21 16:18 ` Alan Cox
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