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