Re: [Publicity] Draft blog post on the ARINC653 scheduler

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On mer, 2013-12-04 at 12:43 -0500, Nate Studer wrote:
> Dario,
> 
Hi Nate!

> It has been awhile, but I finally got a draft blog post giving some basic
> details about the background and algorithm of the ARINC653 scheduler together
> for your review.
> 
> http://blog.xen.org/?p=8453&preview=true
> 
So, first of all, thanks for doing this. Really!

I went through the post, and it already looks pretty good.

They're very minor issues but can you, perhaps, make the pictures a bit
bigger. It would be perfect if you could make them fit the width of the
text area of the blog. I see they're 300px right now... I think 450 or
500 would do.

Also, could you link to either an official specs of ARINC653 or, at
minimum, its Wikipedia page (or something similar)? Could this
"[EASA.2011/6 MULCORS - Use of Multicore Processors in airborne
systems]" be a hyperlink to (perhaps to this page
http://www.easa.europa.eu/safety-and-research/research-projects/large-aeroplanes.php
 or to whatever else you think it's best)?

> Any ideas on how to make the pictures look better are appreciated.
> 
Ok, here they are some more substantial thoughts and comments:

 - in the background, you mention how important isolation is in avionics
   systems and I think (also considering my background) I actually see
   it. Still, could you provide an example on what the various
   components needing to be isolated between each others are. It doesn't
   have to be 100% accurate, just give people an idea what kind of
   subsystems/software we're talking about. Also, what's the role of
   virtualization in that? I mean, I got that an ARINC scheduler
   guarantees strict temporal isolation, but, is using virt --and then
   having an ARINC scheduler in the hypervisor-- common or is an actual
   added value? Can the same be achieved by "just" an OS providing an
   ARINC scheduler and the different components being different
   processes? If no (i.e., if you think virt is actually better), why is
   that?

 - I see you never mention the fact that the scheduler has been
   implemented and is being maintained by DornerWorks. Well, we are an
   Open Source community, so it definitely does not matter much what
   company does the work but, in this case, I think it's a relevant
   piece of information. At least only as an historical note, I think
   I'd say that somewhere (perhaps linking here
http://dornerworks.com/news/2010/12/dornerworks-releases-prototype-arinc-653-hypervisor-to-open-source-community/
   or wherever you think it's appropriate).

 - Related to the above, I think it would be nice to have a few words
   about how and for what you have used it (up to what can be said in a
   post like this, of course). Even better (related to the first point),
   why Xen was chosen in the first place and it is being maintained. As
   you know, we're starting to see interest in embedded virtualization,
   and the view of an early adopter, like you are, on why Xen could be
   the right choice there would be *gold*, or at least so I think.

 - I see you mention "worst case running times" and I think people may
   ask *the* question: <<how in h%$l do you compute that?>>. However,
   this is probably a topic for another post, as giving details about
   this would be both too technical and too long... But personally, I'm
   really curious on whether you actually do that, and, if yes, how,
   especially with the hypervisor in your way! :-)

Again, I'm fine with the content as is... All I did above was sort of
thinking out loud. :-) So, if, for any reason, you don't like or don't
think any of the above is appropriate, just ignore me. :-)

Thanks again and Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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