Routing benchmarks

[Jacques Fourie]

Hi,

I've performed some benchmark tests on my Gumstix Connex 400 (Intel
Xscale PXA 255 CPU clocked at 400MHz) with a netDuo expansion board.
This board has two smc network interfaces. I configure the gumstix as
a router and measure network throughput with netperf running on
seperate boxes on either side of the gumstix. My initial tests showed
a TCP throughput of 2Mbit/s. After adapting the smc driver to use DMA
this figure went up to 7Mbit/s. Although this is a significant
improvement, it still seems to be a bit slow. Does anyone have any
tips on how I can go about to try and figure out where the bottleneck
lies?  Initial profiling showed that a significant amount of time was
spent doing memory to memory copies of data, but after the DMA change
profiling does not show any obvious culprits.

Jacques