Re: bonus inheritance

[Kurt Garloff <garloff@suse.de>]

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Hi Nick,

On Tue, Mar 16, 2004 at 04:54:49PM +1100, Nick Piggin wrote:
> Does it help any actual interactivity problem? Unfortunately
> practically any you make to the scheduler is bound to make
> things worse for at least one person, so it is difficult to
> just test things out.

Well, the interactivity problems existed with O(1) in 2.4.
The 50% penalty hurt freshly started processes a lot.

To fix this, the penalty has been set to 95 (5% penalty)
in 2.6.
I believe it's cleaner to draw the bonus towards the average 
and inherit a percentage, and thus I set a inheritance percentage 
of 50 in 2.4.

It was successful in 2.4. In a measurable way.

In 2.6, it likely will not make a big difference as with giving 
95% of the bonus, you don't change much ...

So it's more a question of have the concept in there which is
clearer. More a theoretical thing. Assuming that with 95% chance
your child has the same character w.r.t. to interactiveness is
rather high.

It will be very hard to measure 80% inheritance to 95% penalty 
as for the most important case (starting a process from a shell), 
the results are almost the same.

The fact that we are more likely to start new processes towards 
the center in our bonus scale certainly makes it faster for the
scheduler to put them in the right category, so there should be
some benefit w.r.t. interactiveness. However, those are not easy 
to measure :-(

I'll see whether we can get some benchmarks anyway.

Regards,
-- 
Kurt Garloff  <garloff@suse.de>                            Cologne, DE 
SUSE LINUX AG, Nuernberg, DE                          SUSE Labs (Head)

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