Chris Snook wrote:
A fraction of *each* CPU, or a fraction of *total* CPU? Per-cpu granularity doesn't make anything more fair.
Well, our current solution uses per-cpu weights, because our vendor couldn't get the load balancer working accurately enough. Having per-cpu weights and cpu affinity gives acceptable results for the case where we're currently using it.
If the load balancer is good enough, per-system weights would be fine. It would have to play nicely with affinity though, in the case where it makes sense to lock tasks to particular cpus.
If I have two threads with the same priority, and two CPUs, the scheduler will put one on each CPU, and they'll run happily without any migration or balancing.
Sure. Now add a third thread. How often do you migrate? Put another way, over what time quantum do we ensure fairness?
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