Re: Need help to measure and tune the latency in Linux RT

On 04/30/2013 03:27 AM, Ashoka K wrote:
> Hi,
>
> I have an embedded system running 2.6.33 cross compiled for ARM OMAP
> with 1 GHZ uni-processor system.

A project I am working on is using the same vintage kernel with RT 
patches applied, though on DaVinci (omap l138).

I, myself, however, have not dealt with any of that work, but I will ask 
the other developer if he has any suggestions.


>
> The application has many threads and processes (around 15 total). In
> that 1 thread is time critical and must run every interval confiurable
> as 2, 4 or 8 milli sec etc. There is another thread which transfers
> Images to a FTP or to HMI etc, whoever requested the image.
> With this image transfer enabled my critical process misses the
> deadline and timesout. This critical thread is at RR priority 50. I
> used a HR timer thread with RR pri 55 to wakeup the critical thread
> every 1 milli sec to do the job.
> If image transfer is enabled i see that real time thread misses deadlines.
>
> All traffic is flowing on common ethernet connection. Does it affect
> in any way ?
>
> How to find out where the kernel is waiting or delaying to schedule
> the critical thread even though it is at higher RR priority. How to
> measure the latency ?
>
> I am trying to use Oprofile tool, but got some error in cross
> compiling. Doesn't these tools add their own latency to the original
> problem ?
>
> Any tools ? which one is better. Please provide your input on this.
>
>
> Regards
> Ashoka.  K
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