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Re: Promblem with PREF (prefetching) in memcpy

To: Hartvig Ekner <hartvige@mips.com>
Subject: Re: Promblem with PREF (prefetching) in memcpy
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Date: 05 Oct 2002 16:56:16 +0100
Cc: Ralf Baechle <ralf@linux-mips.org>, "Kevin D. Kissell" <kevink@mips.com>, Dominic Sweetman <dom@algor.co.uk>, Carsten Langgaard <carstenl@mips.com>, linux-mips@linux-mips.org
In-reply-to: <200210051512.g95FCmI11618@copfs01.mips.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <200210051512.g95FCmI11618@copfs01.mips.com>
Sender: linux-mips-bounce@linux-mips.org
On Sat, 2002-10-05 at 16:12, Hartvig Ekner wrote:
> Whether the last page of physical memory needs to be thrown away or not seems
> like a separate issue. Is this also done in x86 world? What are the issues
> you're thinking about Ralf? Are there devices which will read/write beyond 
> what they have been asked to?

For x86 it isnt done. There are no real wins for prefetching off the end
of memory on x86. Also its important on x86 we don't prefetch into other
memory as we may pull stuff out of the cache of other processors on an
SMP box, and that is expensive


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