Choice of the API for RTEMS v4.8 as a future partition OS for a new LEON compatible open source hypervisor

Joel Sherrill joel.sherrill at
Thu Jan 29 18:11:35 UTC 2009

Ralf Corsepius wrote:
> Metge Jean-Jacques wrote:
>> Hi,
>> Could anybody provide general comparative information between RTEMS API
>> and POSIX API for the v4.8 branch, in terms of :
>> - performances
The performance is going to be comparable within the
bounds of the functionality required by comparable APIs.
All are implemented in terms of SuperCore objects.  Classic
tasks and POSIX threads are all instances of SuperCore threads.
So performance differences should be only in the API adapting
to the SuperCore services.
>> - maturity
I answered this question for someone else last week.

The space community has done their various validation
efforts on the Classic API.   I think this is because it
meets their need and generally Classic API applications
can be slightly smaller executables.  That is important to

The RTEMS POSIX API implementation has been there at least
10 years and the RTEMS test coverage is comparable between
Classic and POSIX APIs.  From my perspective, their maturity is

If you want to contribute to or sponsor improving test coverage,
then please contact me.  We want the standard test suite to
get as close as possible to covering 100% of the source code.
I think this would be valuable to the ESA community long term
and something they should sponsor the core RTEMS developers
to do.

>> In a more general way, any feeback on POSIX API of RTEMS v4.8 will be
>> highly appreciated.
> I would not choose rtems-4.8 for a new project, because it's in "deep 
> freeze maintenance" - i.e. more dead than alive.
> That said, depending on your schedule/time constraints, I'd would choose 
> 4.9 or even RTEMS CVS.
Agreed.  You should try to stay with a recent version.

> Ralf
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Joel Sherrill, Ph.D.             Director of Research & Development
joel.sherrill at        On-Line Applications Research
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