RE: FreeBSD, SMP and Performance Speeds?

> > >But then, even
> > >measuring the process time to run a single simple script 
> shows ~half the
> > >speed with SMP enabled.
> 
> That sounds wrong if the system is being compared to a UP kernel.
> 
> What is the script actually DOING?

This particular script was likely running a single process and not utilizing
multi-proc functionality.

> Stephen, If you could tell us a little more about th e exact 
> tests  you
> are seeing we may be able to improve them a little but it's 
> unlikely that
> we can do much about network throughput.. This is the same 
> problem that
> Linux had in their earlier MP kernels. 

The tests I am running are scripts that allow a tester to setup 10 separate
processes on the server to run 10 separate netperf sessions simultaneously
to ten clients, measuring the throughput speed of each session separate and
summed.  And again, when similar tests were run using iperf and nttcp, the
same performance hits were noted with SMP running.

> It is possible that we can reduce the contention fot the kernel
> by tuning things if we knew exactly what the system, was 
> doing, but it's
> also possible that we can't.. The 40% drop 
> (or was that 40% of throughput?) seems a bit much so it's 
> likely we can do
> SOMETHING.

It was a 40% drop in throughput, which surprised us.  Your consideration is
greatly appreciated.  However, we are likely not in a position where tuning
each box to maximize throughput is a viable option.  These are, after all,
test boxes, not 'performance' boxes.  We are testing NICs and drivers here
and the purpose of my original post was to determine if the performance drop
we were seeing using SMP was expected.  I'm still not clear on whether it is
expected or not.

It's rather important that we are testing with release versions of FreeBSD,
as we are testing for 'the real world', although there are certainly times
when we have the bandwidth to test upcoming releases.  So, if I am reading
you BSD gurus correctly, what I am seeing is (more or less) to be expected,
and it may be in our best interest to wait for a release where this issue is
resolved.

Am I reading this correctly?

Thanks again for your patience and guidance.

Sincerely -

    -=C. Stephen Frost=-
       Intel Corp.
       ICG - Network Quality Labs
       Software Test Engineer
       503.264.8300

Opinions are my own, not those of Intel Corp.

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