Re: RFC: THE OFFLINE SCHEDULER

Ingo Molnar
2009-08-26T21:08:42Z

* Christoph Lameter <cl@linux-foundation.org> wrote:

> > to have sharp teeth nor any apparent poison fangs) - i simply
> > concur with the reasons Peter listed that it is a technically
> > inferior solution.
>
> Ok so you are saying that the reduction of OS latencies will make
> the processor completely available and have no disturbances like
> OFFLINE scheduling?

I'm saying that your lack of trying to reduce even low-hanging-fruit
latency sources that were pointed out to you fundamentally destroys
your credibility in claiming that they are unfixable for all
practical purposes.

Or, to come up with a car analogy: it's a bit as if at a repair shop
you complained that your car has a scratch on its cooler grid that
annoys you, and you insisted that it be outfitted with a new diesel
engine which needs no cooler grid (throwing away the nice Hemi block
it has currently) - and ignored the mechanic's opinion that he loves
the Hemi and that to him the scratch looks very much like bird-sh*t
and that a proper car wash might do the trick too ;-)

> Peter has not given a solution to the problem. Nor have you.

What do you mean by 'has given a solution' - a patch?

Peter mentioned a few things that you can try to reduce the
worst-case latency of the timer tick.

Peter also implemented the hr-tick solution (CONFIG_SCHED_HRTICK) -
it's mostly upstream but disabled because it had problems - if you
are interested in improving this area you can fix and complete it.

That would benefit ordinary Linux users too, not just rare isolation
apps.

Ingo