Messages in this thread | | | Subject | Re: [ckrm-tech] Re: [PATCH 0/9] CPU controller | From | Mike Galbraith <> | Date | Fri, 28 Apr 2006 11:35:06 +0200 |
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On Fri, 2006-04-28 at 12:13 +0400, Kirill Korotaev wrote: > >>>I'm also pretty sure, that CPU controller based on timeslice tricks > >>>behaves poorly on burstable load patterns as well and with interactive > >>>tasks. So before commiting I propose to perform a good testing on > >>>different load patterns. > >> > >>Yes, it can only react very slowly. > > > > > > Actually, this might not be that much of a problem. I know I can > > traverse queue heads periodically very cheaply. Traversing both active > > and expired arrays to requeue starving tasks once every 100ms costs max > > 4usecs (3GHz P4) for a typical distribution. > > with fair scheduling with can be a big problem, as tasks working less > then a tick are hard to account :/
Yeah, tasks dodging the timer interrupt can steal considerable time. I instrumented this once, and caught tasks stealing in excess of 30% of the timeslice of their more lethargic brothers. Generally, they get caught often enough that statistics ~evens the playing field.
-Mike
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