Re: [PATCH] cpuset and sched domains: sched_load_balance flag

Nick Piggin
2007-10-03T13:03:42Z

On Wednesday 03 October 2007 22:17, Paul Jackson wrote:
> Nick wrote:
> > OK, so I don't exactly understand you either. To make it simple, can
> > you give a concrete example of a cpuset hierarchy that wouldn't
> > work?
>
> It's more a matter of knowing how my third party batch scheduler
> coders think. They will be off in some corner of their code with a
> cpuset in hand that they know is just being used to hold inactive
> (paused) tasks, and they can likely be persuaded to mark those cpusets
> as not being in need of any wasted CPU cycles load balancing them.

There won't be any CPU cycles used, if the tasks are paused (surely
they're not spin waiting).

> But these inactive cpusets will overlap in unknown (to them at
> the time, in that piece of code) ways with other cpusets holding
> active jobs, and there is no chance, unless it is a matter of major
> performance impact, that they will be in any position to comment on
> the proper partitioning of the sched domains on all the CPUs under the
> control of their batch scheduler, much less comment on the partitioning
> of the rest of the system.