Re: bifurcated results from netperf

Rick Jones (
Mon, 12 Apr 1999 11:17:35 -0700

My favorite candidate for performance evil is lost packets. Check the
netstat stats when the test runs poorly and compare with when it runs

rick jones

Greg Tillman wrote:
> 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
> numbers:
> 11,82,12,12,83,13,11,14,12,83,83,60,83,12,83,44,83,83,83,14
> Ok, i thought, that will smooth out if we up it to 60 seconds. But, as
> they say, "NOT":
> 83,13,13,83,83,83,15,12,12,13,83,13,83,13,83,12,82,83,14,83
> 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
> insight.
> Thanks for any help.
> - greg tillman
> university of maine at farmington

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