Re: [ck] Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]

Chris Friesen
2007-04-18T19:28:39Z

Mark Glines wrote:

> One minor question: is it even possible to be completely fair on SMP?
> For instance, if you have a 2-way SMP box running 3 applications, one of
> which has 2 threads, will the threaded app have an advantage here? (The
> current system seems to try to keep each thread on a specific CPU, to
> reduce cache thrashing, which means threads and processes alike each
> get 50% of the CPU.)

I think the ideal in this case would be to have both threads on one cpu,
with the other app on the other cpu. This gives inter-process fairness
while minimizing the amount of task migration required.

More interesting is the case of three processes on a 2-cpu system. Do
we constantly migrate one of them back and forth to ensure that each of
them gets 66% of a cpu?

Chris