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

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

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.
> >
> > Peter
> > 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
--
Peter Williams                                   pwil3058@bigpond.net.au

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