Re: [patch] CFS scheduler, -v8

William Lee Irwin III
2007-05-02T19:10:13Z

At some point in the past, Ting Yang wrote:
>> Based on my understanding, adopting something like EEVDF in CFS should
>> not be very difficult given their similarities, although I do not have
>> any idea on how this impacts the load balancing for SMP. Does this worth
>> a try?
>> Sorry for such a long email :-)

On Wed, May 02, 2007 at 11:42:20AM -0700, Li, Tong N wrote:
> Thanks for the excellent explanation. I think EEVDF and many algs alike
> assume global ordering of all tasks in the system (based on virtual
> time), whereas CFS does so locally on each processor and relies on load
> balancing to achieve fairness across processors. It'd achieve strong
> fairness locally, but I'm not sure about its global fairness properties
> in an MP environment. If ideally the total load weight on each processor
> is always the same, then local fairness would imply global fairness, but
> this is a bin packing problem and is intractable ...

It's sort of obvious how to approximate it, but not entirely obvious
whether a given approximation actually suffices. More help with the
theoretical aspects is needed.

- wli