From: Hartvig Ekner <hartvige@mips.com>
To: alan@lxorguk.ukuu.org.uk (Alan Cox)
Cc: carstenl@mips.com (Carsten Langgaard),
dom@algor.co.uk (Dominic Sweetman),
ralf@linux-mips.org (Ralf Baechle),
linux-mips@linux-mips.org
Subject: Re: Promblem with PREF (prefetching) in memcpy
Date: Fri, 4 Oct 2002 15:07:02 +0200 (MEST) [thread overview]
Message-ID: <200210041307.g94D72G02838@copfs01.mips.com> (raw)
In-Reply-To: <1033736983.31861.26.camel@irongate.swansea.linux.org.uk> from "Alan Cox" at Oct 04, 2002 02:09:43 PM
Yes, I think that must be the safest solution.
Any kernel routine which uses PREF instructions (but actually also user
space code as Ralf's example pointed out), must guarantee that it does
not issue prefetches to addresses which it is not specifically being
asked to mess around with.
The other solutions seem too fragile, and will break at some point.
/Hartvig
Alan Cox writes:
>
> On Fri, 2002-10-04 at 13:35, Carsten Langgaard wrote:
> > That's exactly the problem.
> > The actually loads and stores in memcpy is fine, it's the prefetching that
> > prefetch too much.
>
> Then fix your prefetching code 8). We had problems with that on x86 too,
> prefetching off the last page into ISA space -> death. Was umm fun to
> debug
>
>
>
--
_ _ _____ ____ Hartvig Ekner Mailto:hartvige@mips.com
|\ /| | |____)(____ Direct: +45 4486 5503
| \/ | | | _____) MIPS Denmark Switch: +45 4486 5555
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WARNING: multiple messages have this Message-ID (diff)
From: Hartvig Ekner <hartvige@mips.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Carsten Langgaard <carstenl@mips.com>,
Dominic Sweetman <dom@algor.co.uk>,
Ralf Baechle <ralf@linux-mips.org>,
linux-mips@linux-mips.org
Subject: Re: Promblem with PREF (prefetching) in memcpy
Date: Fri, 4 Oct 2002 15:07:02 +0200 (MEST) [thread overview]
Message-ID: <200210041307.g94D72G02838@copfs01.mips.com> (raw)
Message-ID: <20021004130702.njhUd8KAb-aXfUmIzZE0P0tJKlMKFTCremPCzpV5_jg@z> (raw)
In-Reply-To: <1033736983.31861.26.camel@irongate.swansea.linux.org.uk> from "Alan Cox" at Oct 04, 2002 02:09:43 PM
Yes, I think that must be the safest solution.
Any kernel routine which uses PREF instructions (but actually also user
space code as Ralf's example pointed out), must guarantee that it does
not issue prefetches to addresses which it is not specifically being
asked to mess around with.
The other solutions seem too fragile, and will break at some point.
/Hartvig
Alan Cox writes:
>
> On Fri, 2002-10-04 at 13:35, Carsten Langgaard wrote:
> > That's exactly the problem.
> > The actually loads and stores in memcpy is fine, it's the prefetching that
> > prefetch too much.
>
> Then fix your prefetching code 8). We had problems with that on x86 too,
> prefetching off the last page into ISA space -> death. Was umm fun to
> debug
>
>
>
--
_ _ _____ ____ Hartvig Ekner Mailto:hartvige@mips.com
|\ /| | |____)(____ Direct: +45 4486 5503
| \/ | | | _____) MIPS Denmark Switch: +45 4486 5555
T E C H N O L O G I E S http://www.mips.com Fax...: +45 4486 5556
next prev parent reply other threads:[~2002-10-04 13:07 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-04 7:50 Promblem with PREF (prefetching) in memcpy Carsten Langgaard
2002-10-04 11:53 ` Dominic Sweetman
2002-10-04 12:11 ` Carsten Langgaard
2002-10-04 12:35 ` Dr. David Alan Gilbert
2002-10-04 12:36 ` Alan Cox
2002-10-04 12:35 ` Carsten Langgaard
2002-10-04 13:09 ` Alan Cox
2002-10-04 13:07 ` Hartvig Ekner [this message]
2002-10-04 13:07 ` Hartvig Ekner
2002-10-04 13:00 ` Kevin D. Kissell
2002-10-04 13:00 ` Kevin D. Kissell
2002-10-04 13:15 ` Alan Cox
2002-10-04 13:15 ` Kevin D. Kissell
2002-10-04 13:15 ` Kevin D. Kissell
2002-10-04 13:44 ` Alan Cox
2002-10-04 14:17 ` Kevin D. Kissell
2002-10-04 14:17 ` Kevin D. Kissell
2002-10-04 14:54 ` Alan Cox
2002-10-04 13:01 ` Maciej W. Rozycki
2002-10-04 13:17 ` Ralf Baechle
2002-10-04 13:32 ` Maciej W. Rozycki
2002-10-04 13:29 ` Dominic Sweetman
2002-10-04 13:46 ` Maciej W. Rozycki
2002-10-04 12:33 ` Hartvig Ekner
2002-10-04 12:33 ` Hartvig Ekner
2002-10-04 12:38 ` Ralf Baechle
2002-10-04 12:36 ` Kevin D. Kissell
2002-10-04 12:36 ` Kevin D. Kissell
2002-10-04 14:24 ` Dominic Sweetman
2002-10-04 14:24 ` Dominic Sweetman
2002-10-04 23:43 ` Ralf Baechle
2002-10-05 15:12 ` Hartvig Ekner
2002-10-05 15:12 ` Hartvig Ekner
2002-10-05 15:56 ` Alan Cox
2002-10-04 12:37 ` Kevin D. Kissell
2002-10-04 12:37 ` Kevin D. Kissell
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