bifurcated results from netperf

Mon, 12 Apr 1999 12:37:10 -0400

Ok, I know i'm out of my field here, but i'd appreciate any help. I'm
using netperf to test the performance between a pair of Intel's
EtherExpress Pro/100 100Mbs cards, each on a Linux box (RedHat 5.2, kernel
2.0.36). I'm just running a basic

netperf -l 30 -H boxb

The results from a series of 30-second tests seem to be bifurcated,
clustering around either 12 or 80 Mbs, which are obviously way different


Ok, i thought, that will smooth out if we up it to 60 seconds. But, as
they say, "NOT":


Even at 30 minutes, it is by no means nice and smooth and repeatable,
although it's not as bad as the shorter tests. But if anyone can give me a
hint what's going on here, I'd appreciate it. One box has 2 network cards,
because I wanted to test it as a router (once I had some baseline numbers
to compare the router performance to :-( But anyway, I don't see why two
cards in a box should matter. I've cut down on the number of other
processes running on each box to the bare minimum. Each box has 32MB of
memory, which should be plenty to prevent any kind of swapping. I've
toggled the '-- -D' option, to no effect. Debug output doesn't give me any

Thanks for any help.

- greg tillman
university of maine at farmington