Fri Aug 14 12:44:17 1998
Thanks for the quick reply. I tried the v1.02 version without
modification with no luck. I also tried setting bit 5 in the
Cnfg register as shown in your patch, and still saw ttcp and
I have no genuine need to boost the MTU, but was curious as to
any effects on performance. I recently talked with a fellow from
KEK in Japan who'd used MTU=9000 on an Ultrasparc, running the
PacketEngines driver under Solaris. He saw netperf numbers go
from about 180 Mbps with MTU of 1500 to about 280 Mbps with the
> On Thu, 13 Aug 1998, Don Holmgren wrote:
> > Should I be able to successfully use MTU values other than
> > 1500? Using the "mtu=" option when loading the yellowfin
> > driver works, as reported by 'ifconfig'. However, subsequent
> > ttcp or netperf tests hang. I'm using two GNIC's back-to-back,
> > and have tried MTU's of 2000 and 9000.
> This is an untested "feature", and it only has a chance to work with a link
> between two machines, not through a repeater or switch.
> It depends on the driver version.
> The earliest versions and most recent versions (e.g. v1.02) do work with a
> modified MTU.
> Somewhere in the middle I broke the receive buffer side -- it only allocated
> 1536 byte buffers. The corrected versions use
> yp->rx_buf_sz = (dev->mtu <= 1500 ? PKT_BUF_SZ : dev->mtu + 32);
> rather than
> #define PKT_BUF_SZ 1536
> Hmmm, looking at my notes, getting this work involved setting some other
> bit, which I now can't find in the documentation! It may have been bit 5 in
> register 0xA0:
> - outw(0x01CF, ioaddr + Cnfg);
> + outw(mtu > 1500 ? 0x01EF : 0x01CF, ioaddr + Cnfg);
> Donald Becker email@example.com
> USRA-CESDIS, Center of Excellence in Space Data and Information Sciences.
> Code 930.5, Goddard Space Flight Center, Greenbelt, MD. 20771
> 301-286-0882 http://cesdis.gsfc.nasa.gov/people/becker/whoiam.html
| To unsubscribe, send mail to Majordomo@cesdis.gsfc.nasa.gov, and within the
| body of the mail, include only the text:
| unsubscribe this-list-name firstname.lastname@example.org
| You will be unsubscribed as speedily as possible.