[mythtv] Re: Re: Scheduler behavior, why?

Anduin Withers awithers at anduin.com
Sun Feb 13 03:07:44 UTC 2005


> I think I need to reiterate some of the goals from when the scheduler
> was written.  I thought these were made pretty clear then and are
> captured in the documentation Bruce has written.

I try to read most of -dev, still it takes a bit of digging and derivation
to arrive at how the scheduler works even with the documentation. Especially
regarding behavior that some of us may have foolishly become accustomed to.

> First, above all else, the behavior must be deterministic.  The
> scheduler is run many times and the results can't change just because
> something comes out of the database in a different order.

How many times do I have to hear deterministic before someone realizes that
what I want (and what was there, at least in this aspect) isn't
non-deterministic?

> Maybe there
> are other ways, but to me this implies having specific rules to break
> priority ties when they occur.

In this case some of the rules are simply applied too soon. My issue was
with the order of operation not with your design goals.

> Now, that all being said, I think the SchedMoveHigher behavior can be
> extended to automatically apply to programs of equal priority without
> violating the above goals.  The attached patch attempts to do this for
> anyone who wants to test it.

I think you've done a good job with the scheduler, this is the only case
I've encountered where I disliked what it did by default.

> To anyone unsatisfied with this, they're
> welcome to submit patches or write their own scheduler.

If the expected result of raising an issue is a thread like this one, I
imagine something like that will be the only satisfactory path remaining. I
don't want to write a scheduler (mostly I don't want to maintain one, and
put up with people like me poking at it), I don't want to break your
scheduler, I also don't want you and Mr. Markey to act like I insulted your
lineage. I was fully prepared to send a patch once I had established I
wasn't alone in my confusion/desire/had some inkling I'd be headed down the
right path.

> Now, that all being said, I think the SchedMoveHigher behavior can be
> extended to automatically apply to programs of equal priority without
> violating the above goals.  The attached patch attempts to do this for
> anyone who wants to test it.

Thank you.

-- 
Anduin Withers



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