 | Hi Chris,
I've been looking at the examples and things are pretty spread out. Are
there specific things that I need to look for?
Here are my main questions:
How do I specify an earliest deadline first policy?
How do I specify such a deadline?
How do I deal with messages that have no deadline?
Thanks,
Jas
-----Original Message-----
From: Chris Gill [mailto:cdgill@cse.wustl.edu]
Sent: Friday, January 21, 2005 8:35 AM
To: Jaswinder S. Ahluwalia
Cc: schmidt@cs.wustl.edu; tao-users@cs.wustl.edu
Subject: RE: [tao-users] End To End QoS
Hi Jaswinder,
Please take a look at the examples, all of which use EDF, under
ACE_wrappers/TAO/orbsvcs/examples/RtEC/Federated_Kokyu/ in the
EC_DT_RTAS branch of the CVS repository.
Currently you'll need to use the tag EC_DT_RTAS to check out the branch
from our CVS repository, but we're working to get them merged into the
main trunk shortly.
That code is for a series of tests that also involved other things that
might be useful to you depending on the kinds of QoS you want to provide.
For example, Yuanfang did a lot of work on release guards, as described in
a paper that will appear at RTAS:
http://www.cse.wustl.edu/~cdgill/PDF/Zhang_comparison.pdf
BTW, Yuanfang recommended the chain_test example as the simplest one to
show the use of EDF with the EC.
Hope this helps,
Chris
--------------------------------------------------------------------------
Chris Gill, Assistant Professor Bryan 506
Department of Computer Science and Engineering (314) 935-7538
Campus Box 1045, Washington University cdgill@cse.wustl.edu
One Brookings Drive, St. Louis, MO 63130 www.cse.wustl.edu/~cdgill/
--------------------------------------------------------------------------
On Thu, 20 Jan 2005, Jaswinder S. Ahluwalia wrote:
> Hi Chris,
>
> Thanks for the reply. The information you provided is invaluable. There is
a
> side of me which would like to go through with the second option you have
> provided me. It seems far more interesting to me and is riddled with
> problems that intrigue me. However, I lost a few weeks of time because of
my
> grandmother's death and the first option seems much more practical. Not to
> mention, I already have a look up table built in that associates incoming
> messages with a particular sequence and its deadline and the fact that the
> second option is still a work in progress.
>
> So let's go ahead with the first option. Can you give me some guidance on
> how to implement such a policy? Where and how do I specify the deadlines?
> How do I set the policy earliest deadline first? Do I register all
messages
> or just the messages associated with sequences with deadlines? (Not all
> sequences have deadlines). How do I register such messages?
>
> Here is a line of code. As u can see, the rt_info structure is null.
>
>
> supplierPublications.insert( this->myEventSource,// Supplier's unique id
> *j, // Event type
> 0, // handle to the rt_info structure
> 1); // number of calls
>
>
> I greatly appreciate the help you're giving me.
>
> Thanks,
> Jas
>
> -----Original Message-----
> From: Chris Gill [mailto:cdgill@cse.wustl.edu]
> Sent: Thursday, January 20, 2005 2:05 PM
> To: Jaswinder S. Ahluwalia
> Cc: schmidt@cs.wustl.edu; tao-users@cs.wustl.edu
> Subject: Re: [tao-users] End To End QoS
>
> Hi Jas,
>
> Sorry again for the long delay responding - I've finally gotten back on
> top of things and am ready to rejoin the discussion.
>
> To catch back up on the discussion, if I understand correctly the diagram
> you sent shows that the "sequences" you're trying to schedule are
> partially ordered sets of messages, with constraints that could range
> anywhere from ensuring a total order (for example, a before b before c
> before d before e) to allowing any order whatsoever - is that right?
>
> Assuming I have the right picture, I see two ways to go about scheduling
> them:
>
> (1) The simplest way is to just have a deadline for the entire sequence
> (kept say in a table, indexed by the sequence id) and then schedule
> each message according to that deadline. That would ensure that any
> combination of messages contending to be scheduled that are from the
> same sequence would be treated equivalently. That would then let
> you implement sequence scheduling directly using EDF.
>
> (2) If you want to exploit what knowledge you do have (for example,
> registering supplier-consumer dependencies with the scheduler and
> then exporting that graph from the scheduler, or writing a new
> scheduling strategy that could reflect on those dependencies), you
> could take the more difficult route of expressing progress along a
> particular chain of dependencies in your messages and then using that
> information to enforce particular policies for the scheduling order of
> messages within a sequence.
>
> For example using the sequence example you gave earlier, if messages a
> and b have already been scheduled previously and then messages c and d
> arrive and are contending for scheduling, knowing that c was the end
> of a chain and d was the start of a chain within the overall sequence
> could be a key factor for how the scheduler should order c and d
> relative to each other.
>
> We've written a paper on this more selective kind of scheduling for
> the upcoming RTAS conference, which you can find at
>
> www.cse.wustl.edu/~venkita/publications/subramonianv_groupsched.pdf
>
> which shows that this kind of approach is useful for applications
> requiring more sophisticated scheduling decisions than are offered
> by simpler heuristics like EDF, RMS, etc. We are working toward a
> version of the middleware scheduler described there that is portable
> across OS platforms and is integrated into ACE and TAO, but that is
> still an ongoing background task at present.
>
> Hope this helps, and please let me know your thoughts on which of these
> two approaches best matches the needs of the application domain(s) you're
> planning to address.
>
> Thanks,
>
> Chris
>
> --------------------------------------------------------------------------
> Chris Gill, Assistant Professor Bryan 506
> Department of Computer Science and Engineering (314) 935-7538
> Campus Box 1045, Washington University cdgill@cse.wustl.edu
> One Brookings Drive, St. Louis, MO 63130 www.cse.wustl.edu/~cdgill/
> --------------------------------------------------------------------------
>
>
> On Tue, 18 Jan 2005, Jaswinder S. Ahluwalia wrote:
>
> > Hi Everyone,
> >
> > I was having a discussion regarding specifying and implementing
end-to-end
> > qos requirements in the real time event service. Mainly, it was Chris
who
> > was engaing in the discussion, but he left on vacation and two weeks ago
> my
> > grandmother passed away so I've been out of the country. I would like to
> > continue the discussion and get some help on how to have the rt event
> > service enforce a qos requirement on a sequence of messages. How do I
> > specify the timing requirement? How do I specify the dependencies? Etc.
> etc.
> >
> >
> > I look forward to your responses.
> >
> > Thanks,
> > Jas
> >
>
>
|
|
