William Lee Irwin III wrote:
> On Fri, Apr 13, 2007 at 10:21:00PM +0200, Ingo Molnar wrote:
> > [announce] [patch] Modular Scheduler Core and Completely Fair Scheduler
> > [CFS] i'm pleased to announce the first release of the "Modular
> > Scheduler Core and Completely Fair Scheduler [CFS]" patchset:
> > http://redhat.com/~mingo/cfs-scheduler/sched-modular+cfs.patch
> > This project is a complete rewrite of the Linux task scheduler. My goal
> > is to address various feature requests and to fix deficiencies in the
> > vanilla scheduler that were suggested/found in the past few years, both
> > for desktop scheduling and for server scheduling workloads.
> > [ QuickStart: apply the patch to v2.6.21-rc6, recompile, reboot. The
> > new scheduler will be active by default and all tasks will default
> > to the new SCHED_FAIR interactive scheduling class. ]
>
> A pleasant surprise, though I did see it coming.
Same here, but I didn't expect it so soon. Thanks!
> > The CFS patch uses a completely different approach and implementation
> > from RSDL/SD. My goal was to make CFS's interactivity quality exceed
> > that of RSDL/SD, which is a high standard to meet :-) Testing
> > feedback is welcome to decide this one way or another.
I slammed this patch on 2.6.20.6 with some ugly rejects but it did compile,
then tested, so my results may be affected by the rejects.
Boot into /bin/sh.
Run chew.c on three different VT's with different nice each. Observe.
Console 1:
pid 615, prio 19, out for 19 ms, ran for 0 ms, load 4%
pid 615, prio 19, out for 19 ms, ran for 0 ms, load 4%
pid 615, prio 19, out for 19 ms, ran for 0 ms, load 4%
pid 615, prio 19, out for 19 ms, ran for 0 ms, load 4%
pid 615, prio 19, out for 77 ms, ran for 0 ms, load 1%
pid 615, prio 19, out for 125 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 209 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 346 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 552 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 882 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 1231 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 1335 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 1218 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 1254 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 1774 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 1946 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 1942 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 2749 ms, ran for 0 ms, load 0%
pid 615, prio 19, out for 3217 ms, ran for 0 ms, load 0%
Console 2:
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 26%
pid 616, prio 0, out for 9 ms, ran for 2 ms, load 24%
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 26%
pid 616, prio 0, out for 9 ms, ran for 2 ms, load 24%
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 26%
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 26%
pid 616, prio 0, out for 9 ms, ran for 2 ms, load 24%
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 26%
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 24%
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 26%
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 26%
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 24%
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 26%
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 24%
pid 616, prio 0, out for 7 ms, ran for 2 ms, load 26%
pid 616, prio 0, out for 8 ms, ran for 2 ms, load 26%
pid 616, prio 0, out for 9 ms, ran for 2 ms, load 24%
pid 616, prio 0, out for 5 ms, ran for 2 ms, load 26%
Console 3:
pid 617, prio -10, out for 3 ms, ran for 8 ms, load 74%
pid 617, prio -10, out for 3 ms, ran for 7 ms, load 72%
pid 617, prio -10, out for 3 ms, ran for 7 ms, load 72%
pid 617, prio -10, out for 3 ms, ran for 8 ms, load 74%
pid 617, prio -10, out for 3 ms, ran for 7 ms, load 72%
pid 617, prio -10, out for 3 ms, ran for 8 ms, load 74%
pid 617, prio -10, out for 3 ms, ran for 7 ms, load 72%
pid 617, prio -10, out for 3 ms, ran for 7 ms, load 72%
pid 617, prio -10, out for 3 ms, ran for 8 ms, load 74%
pid 617, prio -10, out for 3 ms, ran for 7 ms, load 72%
pid 617, prio -10, out for 3 ms, ran for 8 ms, load 74%
pid 617, prio -10, out for 3 ms, ran for 7 ms, load 72%
pid 617, prio -10, out for 3 ms, ran for 7 ms, load 72%
pid 617, prio -10, out for 3 ms, ran for 8 ms, load 74%
pid 617, prio -10, out for 3 ms, ran for 7 ms, load 72%
pid 617, prio -10, out for 3 ms, ran for 8 ms, load 74%
pid 617, prio -10, out for 3 ms, ran for 7 ms, load 72%
pid 617, prio -10, out for 3 ms, ran for 7 ms, load 72%
It looks like negative nice affects positive nice adversely.
> > CFS's design is quite radical: it does not use runqueues, it uses a
> > time-ordered rbtree to build a 'timeline' of future task execution,
> > and thus has no 'array switch' artifacts (by which both the vanilla
> > scheduler and RSDL/SD are affected).
Sounds interresting, but it looks like CPU-bound procs easily steal sleeping
proc timeslices, thus making it rather unfair, affecting interactivity.
The latencies look great, though.
Also, it may be useful to lower-bound timeslices, as they become ridiculously
small ( < 1ms ).
Thanks!
--
Al
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