Messages in this thread | | | Date | Tue, 24 Jul 2007 17:33:11 -0600 | From | "Chris Friesen" <> | Subject | Re: [RFC] scheduler: improve SMP fairness in CFS |
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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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