5.2.1 netcard performance em slow vs fxp

[Steven Hartland]

Just been testing a em ( gE ) netcard vs a old fxp in the same
machine ( Dual PIII 800 ) and the em can't even match the
fxp for throughput.
Looking at sysstat the interrupt rate on em is virtually double
that of the fxp 11K vs 5k.
When testing with straight ftp from a 2.5Ghz P4 windows 
client using an em connected with a crossover cable I get:
em = 8->9MB/s
fxp = 10->11MB/s

Tweaking the em to use jumbo packets I can push that
to 14MB/s before the cpu on the P3 saturates. This is
mainly interrupt and system time not user ( proftpd ) time.
Unfortunately this doesn't really help because I'm after
increased through put to multiple 100Mb clients not
to one gE client hence jumbo frames is not an option.

Is their anyway to tweak the em driver to give better
performance. I would at least expect as good as the fxp
if not substantially better.
  
  Steve


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