[ECOS] Thread activation disturbed by lower priority threads]

Alois Z. alois@gmx.at
Tue Aug 7 14:02:00 GMT 2007


Hi, 

as I got no response to me questions (see below) I may have to add a few things for clarification.

First of all I'm running an an AT91M5580A processor (thy phytec board). I changed the ecos settings so that the timer tick is now 1ms. The reason for this is that I need such a small tick for my application. Does this anyhow influence the scheduling algorithm. Are there settings that need to be adjusted appart from denominator, nominator and timesclice value?

I did more measurements and found out that the timer DSR is really stable. even more stable than on some other systems (non ecos) I'm using. The problem is that the time between posting on the semaphore (the thread is waiting on) until the thread starts executing  is varying largly. It seems that it is prolonged by other execution elements. And this even when the thread under question is the thread with the highest priority.

would be great if this clearifies my problem a little bit more.

Thanks,
Alois

Hi,

In a larger project I have a problem when doing a timed activation of threads.

In the timer alarm handler I check if any thread is ready for activation and post on a semaphore the thread is waiting for.

This works fine when I have only one or two such timed threads the activation jitter of the thread (i.e. the jitter when the threads starts its execution) is ok. But when I add more threads this jitter grows tremendously. Each thread has an own priority. And event the thread with with the highest priority (in my case 2) has this large jitter (more than half of the cycle time).

Is there a way to improve the behavior of the activation. Do I the timed activation the wrong way. Can I improve the timing behavior of the scheduler through the real-time clock settings.

By the way I use the multilevel scheduler.

Thanks,
Alois



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