real time question : RR vs FF?

Victor henri nadaeck at
Sun May 1 08:54:18 PDT 2011

Hello Stefan and thank you for your answer

> > It was quite easy to find...
> > In the 'testrtpool.c' file, in the 'default-push' function, I just had to
> > replace "SCHED_RR" by "SCHED_FIFO"
> > On the other hand, 'param.sched_priority' is set to to 50, which can be changed
> > also according to the priority one wants to give to the process;
> I hope you have a good reason for using SCHED_FIFO. 1st I hope you understand
> that you will only get scheduling priority, I you are not running fast enough,
> this is *not* the solution

My app is very demanding since it involves realtime (and very fast) analysis and display of the data's. Although my machine is powerfull enough, I suppose that on machine that are not powerfull enough, this could cause lock up.

. 2nd I hope you understand the dangers of SCHED_FIFO
> vs. SCHED_RR.

As far as I know, the  main difference is that the SCHED_FIFO cannot be prempted 
unless another process of higher priority shows up in the execution 
queue; and
SCHED_RR can be preempted by a time quantum... 

I apreciate your warning and get back to the RR policy for now and investigate more. Indeed it may be more safe.

Thank you so much for sharing


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