[realtek] Re: [eepro100] TCP_RR rate, 21143 vs 82559

[Donald Becker]

On Wed, 3 Oct 2001, Kallol Biswas wrote:

>    The netperf TCP_RR transaction rate for 82559 is considerably lower
> than the 21143 for short packets. However for big packets
> 82559 performs better than 21143.

I've Cc:ed this to the tulip mailing list.  Follow-ups should
remove the realtek list unless the message covers the rtl8139.

> The I/O bursts from 21143 are not
> larger than 8 cycles even if other device is not present on the bus, whereas
> 82559 does not relinquish the bus before completing the entire transfer. This
> might cause 82559 card to have better transaction rate for bigger
> packets.

Hmmm, that's unexpected.  IIRC, the 21143 should be configured to do
unlimited bursts.  The settings that control this are in CSR0, although
with the parameters that the BIOS initializes in PCI configuration
space.  The base value of CSR0 is set with the module parameter "csr0",
so it's very easy to test out alternate settings to see if the
performance can be increased.

(Anyone?  There might be an easy 10% decrease in network overhead just
by finding the optimal setting. )

> 21143 is around 15% better than 82559 in terms of 
> transaction rate for the TCP_RR packet size of one byte, but around 8%
> worse for a packet size of 1500 bytes. The break even size if around
> 900 bytes. 

The Tulip has a better descriptor architecture, and is implemented with
hard-wired state machines.  The EEPro100 uses microcode internally, and
thus takes more time between reading the descriptor and transferring
packet data.

> BTW, our lab is shutting down, and I am looking for a job. My resume
> is at: http://resumes.dice.com/kallolbiswas

Good luck.  I was very surprised to see HP abandoning their IA64 effort
and cutting so many highly experienced kernel developers.  It's a pretty
good indication that HP will be focusing their future OS efforts on
something besides HP-UX.


Donald Becker				becker@scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Second Generation Beowulf Clusters
Annapolis MD 21403			410-990-9993