TSO thruput is low !

From: Nagendra Singh Tomar (nagendra_tomar@adaptec.com)
Date: Tue Aug 12 2003 - 06:37:58 EST

I just downloaded 2.6.0-test2 from kernel.org to try the latest TSO
facility. I am having an intel 82545 card.

02:08.0 Ethernet controller: Intel Corp. 82545EM Gigabit Ethernet
Controller (rev 01)

ethtool -k eth2, yields
rx-checksumming: on
tx-checksumming: on
scatter-gather: on
tcp segmentation offload: on

The other side is the same intel NIC on a 2.4.18 (redhat 8.0 kernel), so
TSO is not on.

I am using "ettcp -f 'M' -s -r -p 5003 -l 65535 -n 100000" command.
When I disable TSO with "ethtool -K eth2 tso off" I get around 100MBps
with 30-35% CPU utilization. With TSO on I get ~77MBps with 18-20% CPU
I was expecting a god thruput and low CPU utilization at the same time.

Any suggestions ?


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