Re: 2.6.16-rc5-mm1 -- strange load balancing problems

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Peter Williams wrote:
Peter Williams wrote:

I'm seeing some strange load balancing problems with this kernel. I don't think that they're due to the smpnice patches as I've applied them on a standard 2.6.15-rc5 kernel and the problem doesn't happen there.
The problem is (as I say) quite strange and (for me) very
reproducible. I have two programs (aspin and gsmiley) which I use to
produce CPU hard spinners for testing purposes. What I'm finding is
that when I start several copies of aspin load balancing goes as
expected but when I launch several copies of gsmiley they all go to
the one CPU and stick there like glue. (The most obvious difference
between the two programs is that aspin is just a command line tool
while gsmiley is an X windows program that spins a simley face and
reports its own assessment of the percentage of CPU it's getting.)
The machine that I've seen this problem is a hyper threading Pentium 4
and I suspect that it may be due to the SCHED_MC changes which overlap
SCHED_SMT a bit.
I'm trying to test this on a non hyper threading machine but the
machine has crashed (different kernel) while doing the build. I'll
resume this effort tomorrow but I thought that I should report the
problem so that others could comment.
PS SCHED_MC was configured in but I'll try it without tomorrow and report the results.

Configuring SCHED_MC to "no" causes this problem to go away.
This problem does not appear to be present in 2.6.16-rc6-mm1.

Peter Williams                                   [email protected]

"Learning, n. The kind of ignorance distinguishing the studious."
 -- Ambrose Bierce
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