Re: [PATCH] O3int interactivity for 2.5.74-mm2

Davide Libenzi
2003-07-08T15:05:26Z

On Tue, 8 Jul 2003, Con Kolivas wrote:

> On Tue, 8 Jul 2003 17:46, Davide Libenzi wrote:
> > On Tue, 8 Jul 2003, Szonyi Calin wrote:
> > > In the weekend i did some experiments with the defines in kernel/sched.c
> > > It seems that changing in MAX_TIMESLICE the "200" to "100" or even "50"
> > > helps a little bit. (i was able to do a make bzImage and watch a movie
> > > without noticing that is a kernel compile in background)
> >
> > I bet it helps. Something around 100-120 should be fine. Now we need an
> > exponential function of the priority to assign timeslices to try to
> > maintain interactivity. This should work :
>
> This is still decreasing the timeslices. Whether you do it linearly or
> exponentially the timeslices are smaller, which just about everyone will
> resist you doing.

Maybe you (and this Mr Everyone) might be interested in knowing that the
interactivity is not given by the absolute length of the timeslice but by
the ratio between timeslices. If you have three processes running with
timeslices :

A = 400
B = 200
C = 100

the interactivity is the same of the one if you have :

A = 100
B = 50
C = 25

What changes is the maxiomum CPU blackout time that each task has to see
before re-emerging again from the expired array. In the first case in
"only" 700ms while in the first case is 175ms.

- Davide