Global scheduling in RTEMS

[Joel Sherrill]

On 4/23/2015 8:55 AM, Biermans Joeri wrote:
>
> Hey everyone,
>
>
> I'm a student at the University of Antwerp and I'm
>
> currently working on my master's project.
>
> My master's project is about the comparison
>
> of real-time multicore scheduling algorithms
>
> on embedded systems.
>
>
> I'm currently looking for an RTOS on which
>
> I can add a few global schedulers like G-EDF,
>
> G-RM, RM-US, EDF-US and EDF(k).
>
>
> I came across RTEMS and I have the following
>
> question about the OS:
>
>
> * Is it possible to globally schedule jobs of tasks
>
> in RTEMS? 
>
>
> (ie released/suspended jobs are placed
>
> into a global queue shared between all processors.
>
> The scheduler calculates their priority and decides
>
> on which m cores the m highest priority jobs should 
>
> run. Jobs can migrate between different cores.)
>
>
The answer is yes. RTEMS has a plugin for thread schedulers.
There are multiple uniprocessor and multicore schedulers plus
clustered scheduling.

None of the algorithms you listed are currently available as
SMP schedulers.  EDF is implemented as a uniprocessor scheduler.
It uses (or IMO abuses) thread priority for threads with a deadline.
There is a ticket filed to move the scheduler's notion of "priority"
into a per-thread scheduler specific structure. Currently, the
thread priority is overloaded to have a deadline which is out of
range for legal thread priorities.

There is a Scheduler Simulator which makes it possible to
implement and debug schedulers without hardware. I used
this on the SMP w/affinity and got the algorithm to 100%
test coverage although it did turn out I had tripped a bug
which didn't show up until on real hardware. It would be handy
for you.

I will email some slides on the current state of SMP from
a user perspective but the code itself is all in git and Doxygen
is available.  Please feel free to ask questions as needed.
>
> Thanks in advance.
>
>
> Kind regards,
>
> Joeri
>

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel.sherrill at OARcorp.com        On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
Support Available                (256) 722-9985

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