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Date: Thu, 17 Oct 2002 18:27:29 +0100
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
Message-ID: <20021017172729.GA29177@suse.de>
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	Matthew Wilcox <willy@debian.org>,
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References: <20021017180134.X15163@parcelfarce.linux.theplanet.co.uk>
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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
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