Re: scheduler starvation resistance patches for 2.6.16

[Al Boldi <a1426z@gawab.com>]

Mike Galbraith wrote:
> On Tue, 2006-03-28 at 07:10 +0200, Mike Galbraith wrote:
> > On Mon, 2006-03-27 at 21:36 +0300, Al Boldi wrote:
> > > It's not bad.  w/ credit_c1/2 set to 0 results in an improvement in
> > > running the MESA demos  "# gears & reflect & morph3d" .
> >
> > Hmm.  That's unexpected.
> >
> > > But a simple "# while :; do :; done &" (10x) makes a "# ping 10.1 -A
> > > -s8" choke.
> >
> > Ouch, so is that.  But thanks, testcases are great.  I'll look into it.
>
> OK, this has nothing to do with my patches.  The same slowdown happens
> with a stock kernel when running a few pure cpu hogs.  I suspect it has
> to do with softirqd, but am still investigating.

I think so too.

I played with some numbers inside sched.c.  Raising the MIN_TIMESLICE from 1 
to between 10-100  affects interactivity positively, although it does not 
fix it entirely.

It does look like there is an underlying problem (locking?) that may be 
worked-around by tuning the scheduler to some extent.

Also, MAX_TIMESLICE = 800 seems a bit high.  Can this be lowered?

Thanks!

--
Al

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