Re: [PATCH] 2.6.0 batch scheduling, HT aware

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > > >>>I discussed this with Ingo and that's the sort of thing we thought of.
> > > >>>Perhaps a relative crossover of 10 dynamic priorities and an absolute
> > > >>>crossover of 5 static priorities before things got queued together.
> > > >>> This is really only required for the UP HT case.
> > > >>
> > > >>Well I guess it would still be nice for "SMP HT" as well. Hopefully the
> > > >>code can be generic enough that it would just carry over nicely.
> > > >
> > > >I disagree. I can't think of a real world scenario where 2+ physical
> > > > cpus would benefit from this.
> > >
> > > Well its the same problem. A nice -20 process can still lose 40-55% of
> > > its performance to a nice 19 process, a figure of 10% is probably too
> > > high and we'd really want it <= 5% like what happens with a single
> > > logical processor.
> >
> > I changed my mind just after I sent that mail. 4 physical cores running
> > three nice 20 and one nice -20 task gives the nice -20 task only 25% of the
> > total cpu and 25% to each of the nice 20 tasks.
> 
> Err that should read 4 logical cores.

Actually, for 4 physical cores it is going to be true, too. And if you
are memory-bound, stopping those 3 task can speed your important
task, too. Its really same.
									Pavel
-- 
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]