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Re: Prefetches in memcpy

To: "Ralf Baechle" <ralf@uni-koblenz.de>, "Carsten Langgaard" <carstenl@mips.com>
Subject: Re: Prefetches in memcpy
From: "Kevin D. Kissell" <kevink@mips.com>
Date: Tue, 5 Nov 2002 17:13:48 +0100
Cc: <linux-mips@linux-mips.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <3DC7CB8B.E2C1D4E5@mips.com> <20021105163806.A24996@bacchus.dhis.org>
Sender: linux-mips-bounce@linux-mips.org
From: "Ralf Baechle" <ralf@uni-koblenz.de>
> So I think the fix will have to be:
> 
>  - Avoid prefetching beyond the end of the copy area in memcpy and memmove.
>  - Introduce a second variant of memcpy that never does prefetching.  This
>    one will be safe to use in KSEG1 / uncached XKPHYS also and will be used
>    for memcpy_fromio, memcpy_toio and friends.

Assuming we had a version that prefetched exactly to the end
of the source memory block and no further, why would we need
the second variant?

            Kevin K.

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