Re: [Xen-devel] Should we mark RTDS as supported feature from experimental feature?

[Meng Xu <xumengpanda@xxxxxxxxx>]

>> The feature document template has been put together:
>> http://lists.xenproject.org/archives/html/xen-devel/2015-08/msg01929.html
>>
>> And there are feature documents in tree already.
>>
>> Actually, writing one for RTDS would be a rather interesting and useful
>> thing to do, IMO! :-)
>
> I think it would be helpful to try to spell out what we think are the
> criteria for marking RTDS non-experimental.  Reading your e-mail, Dario,
> I might infer the following criteria:
>
> 1. New event-driven code spends most of a full release cycle in the tree
> being tested
> 2. Better tests in osstest (which ones?)
> 3. A feature doc

I agree with the above three items.

> 4. A work-conserving mode

I think we need to consider the item 4 carefully. Work-conserving mode
is not a must for real-time schedulers and it is not the main
purpose/goal of the RTDS scheduler.

>
> #3 definitely sounds like a good idea.  #1 is probably reasonable.
>
> I don't think #4 should be a blocker; we have plenty of work-conserving
> schedulers. :-)

Exactly.. Actually, work-conserving feature is not a top property for
real-time applications. The resource sharing issues, interacted with
the scheduler, are more important than the work-conserving "issue" for
complex non-independent real-time applications.

>
> Regarding #2, did you have specific tests in mind?

I've been thinking about how to confirm the correctness of (RTDS)
schedulers. It is actually quite challenging to prove the scheduler is
correct.

I'm thinking what the goal of the tests is? It will determine how the
scheduler should be tested, IMHO.
There are three possible goals in increasing difficulty:
(1) Make sure the scheduler won't crash the system, or
(2) make sure the performance of the scheduler is correct, or
(3) prove the scheduler is correct?

Which one are we talking about here? (maybe item 1?)

Thanks,

Meng

-----------
Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania
http://www.cis.upenn.edu/~mengxu/

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