Re: High priority threads causing severe CPU load imbalances

[Peter Zijlstra <peterz@infradead.org>]

On Tue, 2010-04-06 at 22:05 +0530, Suresh Jayaraman wrote:
> Perhaps there is a chance that with more CPUs, different number of high
> priority threads the problem could get worser as I mentioned above..?

One thing that could be happening (triggered by what Igawa-san said,
although his case is more complicated by involving the cgroup stuff) is
that f_b_g() ends up selecting a group that contains these niced tasks
and then f_b_q() will not find a suitable source queue because all of
them will have but a single runnable task on it and hence we simply
bail.

We'd somehow have to teach update_*_lb_stats() not to consider groups
where nr_running <= nr_cpus. I don't currently have a patch for that,
but I think that is the direction you might need to look in.