Re: [ckrm-tech] Re: [PATCH 0/9] CPU controller

[Con Kolivas <kernel@kolivas.org>]

On Friday 28 April 2006 20:16, Mike Galbraith wrote:
> On Fri, 2006-04-28 at 20:09 +1000, Con Kolivas wrote:
> > On Friday 28 April 2006 17:46, Mike Galbraith wrote:
> > > On Fri, 2006-04-28 at 09:11 +0200, Mike Galbraith wrote:
> > > > On Fri, 2006-04-28 at 09:56 +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.
> >
> > How many tasks? Your function was O(n) so the more tasks the longer that
> > max value was.
>
> Nope.  It's not O(tasks), it's O(occupied_queues).  Occupied queues is
> generally not a large number.

Ok well that P4 does about 700,000 context switches per second so 4us sounds 
large to me.

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