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

[Peter Williams <pwil3058@bigpond.net.au>]

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.
Peter
PS SCHED_MC was configured in but I'll try it without tomorrow and 
report the results.
--
Peter Williams                                   pwil3058@bigpond.net.au

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