Messages in this thread | | | Date | Mon, 23 Apr 2007 04:55:53 +0200 | From | Ingo Molnar <> | Subject | Re: [patch] CFS scheduler, -v5 |
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* Nick Piggin <npiggin@suse.de> wrote:
> > the biggest user-visible change in -v5 are various interactivity > > improvements (especially under higher load) to fix reported > > regressions, and an improved way of handling nice levels. There's > > also a new sys_sched_yield_to() syscall implementation for i686 and > > x86_64. > > > > All known regressions have been fixed. (knock on wood) > > I think the granularity is still much too low. Why not increase it to > something more reasonable as a default?
note that CFS's "granularity" value is not directly comparable to "timeslice length":
> [ Note: while CFS's default preemption granularity is currently set to > 5 msecs, this value does not directly transform into timeslices: for > example two CPU-intense tasks will have effective timeslices of 10 > msecs with this setting. ]
also, i just checked SD: 0.46 defaults to 8 msecs rr_interval (on 1 CPU systems), which is lower than the 10 msecs effective timeslice length CVS-v5 achieves on two CPU-bound tasks.
(in -v6 i'll scale the granularity up a bit with the number of CPUs, like SD does. That should get the right result on larger SMP boxes too.)
while i agree it's a tad too finegrained still, I agree with Con's choice: rather err on the side of being too finegrained and lose some small amount of throughput on cache-intense workloads like compile jobs, than err on the side of being visibly too choppy for users on the desktop.
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