Re: sched: fix/optimise some issues

From: Mike Galbraith
Date: Wed Jul 20 2011 - 21:00:22 EST

On Wed, 2011-07-20 at 21:11 +0200, Peter Zijlstra wrote:
> On Wed, 2011-07-20 at 15:42 +0200, Stephan BÃrwolf wrote:
> > In "check_preempt_tick()" (kernel/sched_fair.c:1093) a ulong
> > called "ideal_runtime" stores a timeslice of the current task
> > (scheduling entity). This time complies real cpu-time.
> >
> > At the end of the same function (nr_running > 1) this (real) time
> > is compared with a virtual-runtime-delta. Obviously the timeunits
> > (real vs. virtual) didn't fit.
> >
> > Using "wakeup_preempt_entity()" instead should fix this in a even
> > more general way.

(That's what I thought at first too)

> Hrm,. I'm fairly sure we did that on purpose and the thing that is
> missing is a big fat comment. People keep trying to fix that (me
> included).
> I'll try and dig up the why and such.

Better to just kill it outright. It's not doing that much anyway.


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