RTEMS vs Linux : Performance analysis : Comments andSuggestions Please

[Joel Sherrill]

Ranjith Mukundan wrote:

> and i guess this is without the RT or RTAI patch?? as ralf indicated,
> please provide the details (kernel version, patches & patch levels used
> etc)..

Is caching on with the RTEMS BSP?

Ralf.. you are right.. I need to cut a 4.6.1.  There haven't
been any new 4.6.0 problems reported in the past coup[le of
weeks.

--joel
> -----Original Message-----
> From: Ralf Corsepius [mailto:ralf_corsepius at rtems.org] 
> Sent: Friday, March 19, 2004 4:20 PM
> To: sashti srinivasan
> Cc: RTEMS Users
> Subject: Re: RTEMS vs Linux : Performance analysis : Comments
> andSuggestions Please
> 
> 
> On Fri, 2004-03-19 at 10:47, sashti srinivasan wrote:
> 
>>Hello All,
>>
>>       Because of the full fledged support from the
>>list, I am now able to measure time accurately with 1
>>microsecond accuracy on PC386.  I have got some
>>figures of merit, based on this I want to improve the
>>performance of rtems.  Here are the results for
>>discussion.  This is a comparison between linux and
>>rtems on pc386 platform.  POSIX api is used for the
>>measurement and to the best possible extent same code
>>has been used in both. 
> 
> 
> More details, please.
> 
> How did you measure these figures?
> 
> Which CPU has been used?
> 
> Which compilers, which flags have been used to compile the Linux-Kernel,
> Linux-libc, Linux-application, RTEMS and your RTEMS application?
> 
> 
>> Please suggest some way of
>>improving the performance of rtems in these aspects.
> 
> Number one source of improvement for RTEMS: The compiler flags.
> There, choosing the appropriate set of flags can result into huge
> differences in performance.
> 
> 
>>(All Times are in microseconds : Average of some large
>>number of operations)
>>
>>                              Linux   RTEMS
>>       Time To Lock a Mutex =  0.12   0.30
>>     Time To Unlock a Mutex =  0.12   0.28
>>     Initialize a Semaphore =  0.31   0.99
>>        Destroy a Semaphore =  0.10   1.46
>>             Semaphore Wait =  0.20   0.24
>>             Semaphore Post =  0.19   0.31
> 
> 
> These figures are no actual surprize to me, because Linux pthread
> implementation is pretty low-level, lean and highly optimized for speed,
> while RTEMS's pthreads/posix implementation is a wrapper to RTEMS native
> mechanisms and therefore is comparatively heavy weighted.
> 
> 
>>     Thread Switching Time =  9.85   1.81
> 
> Note this figure above. mutexes and semaphores are only one side of the
> medal ;)
> 
> 
>>    Please suggest some ideas regarding improvement of
>>mutex and semaphore performance of rtems.
> 
> 
> Ralf
> 
> 
> 
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-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel at OARcorp.com                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
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