| To: | "Kevin D. Kissell" <kevink@mips.com> |
|---|---|
| Subject: | Re: Promblem with PREF (prefetching) in memcpy |
| From: | Alan Cox <alan@lxorguk.ukuu.org.uk> |
| Date: | 04 Oct 2002 14:44:06 +0100 |
| Cc: | Carsten Langgaard <carstenl@mips.com>, Dominic Sweetman <dom@algor.co.uk>, Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org |
| In-reply-to: | <010e01c26ba8$2c9400d0$10eca8c0@grendel> |
| Original-recipient: | rfc822;linux-mips@linux-mips.org |
| References: | <3D9D484B.4C149BD8@mips.com><200210041153.MAA12052@mudchute.algor.co.uk> <3D9D855B.12128FA2@mips.com><1033734968.31839.5.camel@irongate.swansea.linux .org.uk> <00fe01c26ba6$04943480$10eca8c0@grendel> <1033737330.31861.30.camel@irongate.swansea.linux.org.uk> <010e01c26ba8$2c9400d0$10eca8c0@grendel> |
| Sender: | linux-mips-bounce@linux-mips.org |
On Fri, 2002-10-04 at 14:15, Kevin D. Kissell wrote:
> 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?
The x86 code basically says
while(over 320 bytes left)
{
prefetch ahead
copy bits
}
while(bytes left)
copy bits
You also have to watch the prefetching in the tcp checksum code. We hit
an x86 bug there also very recently. That one is new but shows up with
the zero copy tcp nfs
|
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