POSIX performance

[Alexander I. Shaykhrazeev]

Thanks for help. :-)
I have additional question about using C++ under RTEMS. Did somebody use 
C++ to create applications for RTEMS?
We have a task better to solve using C++ and mechanism of abstraction, 
but the task need great performance. All task must complete for 1 sec, task
called every 1 sec.
There are any profiler for RTEMS to see process on time diagram? (Such 
instrument was very useful on WindRiver Workbench)

Joel Sherrill wrote:
> Till Straumann wrote:
>
>> Alexander I. Shaykhrazeev wrote:
>>
>>> Did somebody check performance of POSIX semaphores and other 
>>> functions against RTEMS own?
>>>
>>
>> A while ago I compared vxworks, rtems and RT-linux regarding
>> interrupt and thread dispatching latency.
>> Both, rtems native and posix APIs were used.
>>
>> See
>>
>> http://www.slac.stanford.edu/econf/C011127/WEBI001.shtml
>>
>> Note, however, that the paper incorrectly reports poor pthread
>> performance under RTEMS. This was due to a programming error
>> (incorrect task priority assignment). A repeated test using with
>> the correct pthread priority yielded no significant difference in
>> performance between RTEMS native and pthreads (for the
>> latency benchmark - this was not a comprehensive comparison
>> of all features or primitives, however).
>>
> From a design viewpoint, there should be little difference between
> the POSIX and Classic API objects performance.  Many are
> based upon the same underlying SuperCore support and the API
> code is just a thin wrapper.
>
> + POSIX threads and Classic tasks are SuperCore threads
> + POSIX mutex --> SuperCore Mutex
> + POSIX semaphore --> SuperCore Semaphore
> + Classic Semaphore --> SuperCore Mutex or Semaphore
> + POSIX and Classic message queues are SuperCore message queues
>
> All blocking code is the same.  All delays/sleeps end up in the same 
> helper
> routines.
> The primary difference is going to be the overhead of translating the
> API into SuperCore calls -- which should be in the noise as far as
> differences.  The other thing to watch out for is semantic differences
> which means that one API might actually have more functionality
> required from what appears to be the same call.  For example,
> POSIX message queues allow for priority based messages and
> Classic API message queues are FIFO or LIFO.
>
> --joel
>
>> -- Till
>
>
>

-- 
Alexander I. Shaykhrazeev
Morion Inc.