From: "Kevin D. Kissell" <kevink@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 15:15:41 +0200 [thread overview]
Message-ID: <010e01c26ba8$2c9400d0$10eca8c0@grendel> (raw)
In-Reply-To: 1033737330.31861.30.camel@irongate.swansea.linux.org.uk
From: "Alan Cox" <alan@lxorguk.ukuu.org.uk>
> On Fri, 2002-10-04 at 14:00, Kevin D. Kissell wrote:
> > The issue isn't that anyone would deliberately use memcpy() in I/O
> > space. Rather, it's that memcpy() prefetches quite a ways ahead,
> > and if one has I/O space assigned just after the end of physical
> > memory, Bad Things might happen on a perfectly legal memcpy()
> > that references the last couple hundred bytes of memory in a
> > way that not even a clever and well-informed bus error handler
> > could undo.
>
> Then your memcpy function is IMHO broken. Fix it to note prefetch beyond
> the end of the area you actually will copy and life should be a lot
> better
Which is excatly the point that Carsten was raising when he started this thread!
The question is how, i.e. throttle memcpy or thow away a "guard band" of RAM?
Regards,
Kevin K.
WARNING: multiple messages have this Message-ID (diff)
From: "Kevin D. Kissell" <kevink@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 15:15:41 +0200 [thread overview]
Message-ID: <010e01c26ba8$2c9400d0$10eca8c0@grendel> (raw)
Message-ID: <20021004131541.AtYUIKXkJcUQbNNd2QeftMhOmdTIIpiaWzPetO9mGYg@z> (raw)
In-Reply-To: 1033737330.31861.30.camel@irongate.swansea.linux.org.uk
From: "Alan Cox" <alan@lxorguk.ukuu.org.uk>
> On Fri, 2002-10-04 at 14:00, Kevin D. Kissell wrote:
> > The issue isn't that anyone would deliberately use memcpy() in I/O
> > space. Rather, it's that memcpy() prefetches quite a ways ahead,
> > and if one has I/O space assigned just after the end of physical
> > memory, Bad Things might happen on a perfectly legal memcpy()
> > that references the last couple hundred bytes of memory in a
> > way that not even a clever and well-informed bus error handler
> > could undo.
>
> Then your memcpy function is IMHO broken. Fix it to note prefetch beyond
> the end of the area you actually will copy and life should be a lot
> better
Which is excatly the point that Carsten was raising when he started this thread!
The question is how, i.e. throttle memcpy or thow away a "guard band" of RAM?
Regards,
Kevin K.
next prev parent reply other threads:[~2002-10-04 13:13 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
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 [this message]
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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