[ECOS] Re: DSR Scheduling Problem

[Grant Edwards]

In gmane.os.ecos.general, you wrote:

>> Isn't ECOS about choice?

Yes.

> Well, unfortunately choice doesn't come for free.

And the new feature you want does?

> More testing, more opportunities for bugs, more confusion,
> etc. I believe useless choices are evil.

Adding a new DSR scheduler doesn't come for free either.
Keeping the old one, however, _is_ free.

>> Make this configurable option and allow users to try both. :-)
>
> Which of the options do you suggest to be the default?

The existing one, of course.  Always default to existing
behavior when adding new options.

> How do you explain users the criteria to choose one algorithm
> or another?

You don't.  Just explain the differences between the two
algorithms.  It's up to the user to determine the criteria on
which he's making his choice.

> How will user compare the choices in his tests when most of
> time the algorithms behave exactly the same?

That's up to the user.

> How do you explain why LIFO choice is there in the first place
> if it has no advantages?

It's already been explained:  LIFO is fast and dirt-simple.

> For example, the "array" choice for DSR queue does have an
> excuse as being interrupts-disable-free, and it has an excuse
> of not being the default as it has potential problems with
> missing DSRs. What's an excuse for keeping LIFO choice?

The most important excuse is not changing things for people who
have working systems.  I don't care how much you want FIFO DSR
scheduling -- you don't get to force it down my throat.

> The only one I see is backward compatibility, but due to the
> fact that eCos never specified exact order of DSRs it
> shouldn't matter.

Lots of things that shouldn't matter do.  Don't arbitrarily
force changes on everybody just to make a tiny minority happy.
I'm all for allowing that minority to add another DSR
scheduling option if they want.  I'm _not_ for allow them to
force that change on everybody else.

-- 
Grant Edwards                   grante             Yow!  Put FIVE DOZEN red
                                  at               GIRDLES in each CIRCULAR
                               visi.com            OPENING!!

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