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Re: NFS root with cache on

To: ralf@oss.sgi.com (Ralf Baechle)
Subject: Re: NFS root with cache on
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Date: Mon, 5 Feb 2001 21:39:51 +0000 (GMT)
Cc: jsun@mvista.com (Jun Sun), jensenq@Lineo.COM (Quinn Jensen), linux-mips@oss.sgi.com
In-reply-to: <20010205115026.C2487@bacchus.dhis.org> from "Ralf Baechle" at Feb 05, 2001 11:50:26 AM
Sender: owner-linux-mips@oss.sgi.com
> On Mon, Feb 05, 2001 at 10:07:18AM -0800, Jun Sun wrote:
> 
> > Did you set rx_copybreak to 1518?  I sent patches long time ago to the 
> > driver
> > authors for MIPS, but I am not sure they are not there.
> 
> Copybreak is just an optimization.  So even with this unused or set to a
> wrong value the driver should work.

If you set it wrongly you can get network failures/stalls. The normal cases
are not a problem however. You need to copybreak small frames to avoid filling
the socket queue with empty spaces. Some platforms set it to 1518 to force
a copy thereby aligning the IP header on a 4 byte boundary, which most
PCI bus master drivers wont do if you are not copying


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