Re: [9fans] 9bench: lmbench for Plan 9

[erik quanstrom <quanstro@quanstro.net>]

> As for the utility of the benchmarks, come on. I know there are people
> on this list who write kernel code (hmm, I seem to recall somebody
> on here who does a lot of work on networking drivers...) and they
> may find it useful to get these kinds of measurements to see if
> changes have improved performance. Besides, there's nothing to stop you
> from running the benchmarks on Linux and Plan 9 and comparing (for
> yourself) the difference in performance--you just can't try for
> e-cred by posting your results on comp.os.linux (hint: the
> comparisons don't come out very favorably for Plan 9 anyway).

i tend to use very simple timing runs in my testing.  i use dd for AoE
and disk drivers and a small program named zerohose for (other)
network protcols.  time(1) seems good enough for timing given an
appropriate amount of i/o.

the reason for the simple timing tests is because good hardware is
hard to get wrong but marginal hardware (bad design, undersized
buffers, unsufficient pcie lanes) is typically very sensitve to cache
pecularities.  even with simple tests some hardware can have >20%
variance between runs.  it's very hard to reason about this sort of
thing.  i'd hate to have to also have to understand what the benchmark
is doing for^wto me, too.

oh, plan 9 can push packets faster on the nics i've tested than linux,
but for some reason, plan 9 tcp performance hasn't been very good,
especially on 10gbe hardware.  il and aoe fair much better.

- erik