Re: [Discuss-gnuradio] End-to-end delay question

[Eric Blossom]

On Mon, May 21, 2007 at 10:21:48PM -0400, Michael Dickens wrote:
> On May 21, 2007, at 3:04 PM, Eric Blossom wrote:
> >We have the capability to request real time scheduling (currently only
> >on systems that implment POSIX sched_setscheduler), but generally
> >avoid it by default, since folks have been known to frequently blow
> >their own feet off.
> 
> Looking at gnuradio-core/lib/src/runtime/gr_realtime.cc, it seems  
> that the running thread's scheduling is set to FIFO and the priority  
> is maximized.

The priority is set to the midpoint of the FIFO range, not maximized.

> If this is "all" that's being done, then this can be ports to
> pthread's (also supposedly POSIX), as on some BSD (and thus OSX)
> systems.  Instead of "sched_setscheduler" (which sets both the
> scheduling policy and priority), use "pthread_attr_setschedparam"
> and "pthread_attr_setschedpolicy".  I will look into it. - MLD

Michael, I don't think we want to be creating new threads just to try
to set real time scheduling.  I strongly suspect that if a pthread
implementation supports pthread_attr_setschedpolicy with SCHED_RR or
SCHED_FIFO, then they will also implement sched_setscheduler with
SCHED_RR or SCHED_FIFO.

Eric