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

Ingo Molnar
2007-04-14T10:53:49Z

* Willy Tarreau <w@1wt.eu> wrote:

> Forking becomes very slow above a load of 100 it seems. Sometimes, the
> shell takes 2 or 3 seconds to return to prompt after I run "scheddos
> &"

this might be changed/impacted by the parent-requeue fix that is in the
updated (for real, promise! ;) patch. Right now on CFS a forking parent
shares its own run stats with the child 50%/50%. This means that heavy
forkers are indeed penalized. Another logical choice would be 100%/0%: a
child has to earn its own right.

i kept the 50%/50% rule from the old scheduler, but maybe it's a more
pristine (and smaller/faster) approach to just not give new children any
stats history to begin with. I've implemented an add-on patch that
implements this, you can find it at:

http://redhat.com/~mingo/cfs-scheduler/sched-fair-fork.patch

> Those are very promising results, I nearly observe the same
> responsiveness as I had on a solaris 10 with 10k running processes on
> a bigger machine.

cool and thanks for the feedback! (Btw., as another test you could also
try to renice "scheddos" to +19. While that does not push the scheduler
nearly as hard as nice 0, it is perhaps more indicative of how a truly
abusive many-tasks workload would be run in practice.)

Ingo