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Subject: Re: Cache coherency and snooping
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: imran.badr@cavium.com
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <0a9a01c24320$4c936de0$9e10a8c0@IMRANPC>
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Date: 14 Aug 2002 00:38:08 +0100
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On Wed, 2002-08-14 at 00:22, Imran Badr wrote:
> How can I define a certain region of memory so that it is never cached? I
> want to use non-cached region of memory to communicate to my PCI device to
> avoid system overhead in cache snooping.

Architecture specific and for RAM quite often not supported at all. You
can use ioremap_nocache on ram in theory but that doesn't actually work
on most processors, will MCE on the PPro and needs some work on Athlon
XP/MP

K6/K5 don't support it at all from memory.

If your hardware is sane it will already be doing cache line size bursts
and MWI.

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