RTEMS 4.11 runs slower as RTEMS 4.88 on a monoprocessor?

Joel Sherrill joel at rtems.org
Fri May 27 15:07:57 UTC 2016

On Fri, May 27, 2016 at 10:00 AM, Thibaud Backenstrass <
thibaud.backenstrass at phelma.grenoble-inp.fr> wrote:

> Hello,
> I made a comparison of the timing performances of both RTEMS 4.8 and RTEMS
> 4.11 using the exact same application. Basically, the application creates
> and starts a few tasks, then stops them almost immediately. It also
> includes a timing observation service to know how much time each operation
> requires.
> Both RTEMS 4.8 and 4.11 are build with networking, POSIX API and Ada
> support. The application is built the same way and executed under the TSIM
> simulator for SPARC/LEON3, using only one processor.
> I noticed that the execution of my application under RTEMS 4.11 is at
> least 10% slower than under RTEMS 4.8.0 and I am wondering:
> - did the build options (and especially the optimization options) changed
> between RTEMS 4.8 and RTEMS 4.11?
> - is the gcc compiler 4.9.4 less “efficient” than the version 4.2.0 used
> to build RTEMS 4.8.0?
> - is RTEMS 4.11 slower due to the fact that is supports multiprocessor
> (SMP) and that the structures (semaphores, ...) are more time consuming,
> even on a monoprocessor?
All of those are possibilities but I would lean to the third option more.

Is this a C or Ada test?

Can you run the timing tests on both versions so we can see what
operations themselves have gotten slower?

> Or what could be the reasons why RTEMS 4.11 runs slower than RTEMS 4.8 on
> a monoprocessor?
> Thanks in advance for your suggestions and ideas!
> *Thibaud BACKENSTRASS* <thibaud.backenstrass at phelma.grenoble-inp.fr>
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