[Jackit-devel] Re: fc2, xorg, 2.6.x, scheduling latency peaks

[Fernando Pablo Lopez-Lezcano]

> > > Aha! I think you are on to something! I double checked the priority of
> > > the jack clients and _they_ are not getting SCHED_FIFO!! They should be
> > > getting that priority from the jack server but they are not (and the
> > > jack server is not complaining at all so no error is being raised).
> > > Probably some change in glibc, I would think... 
> 
> I had begun to notice some of this, too.  But, I hadn't figured out
> what was going on. 

I have been banging my head on walls for a while trying to find out what
was causing the xruns...

> > Just confirmed this with a first preliminary hack (and test). Jack
> > creates new threads and to do that it sets up a pthread_attr_t struct
> > and uses pthread_attr_setschedpolicy and pthread_attr_setscope to set
> > the scheduling policy (and also sets the priority) in the struct. Then
> > pthread_create is called (with that struct as an argument) and the
> > thread is created. But the thread created is _not_ SCHED_FIFO and there
> > is no error return. If _after_ the thread is created I double check the
> > scheduling policy and use pthread_setschedparam to again set it to
> > SCHED_FIFO then the thread changes to SCHED_FIFO... go figure...
> 
> Is this only with NPTL or on any 2.6.6 system?

I have only tested on FC2 and 2.6.6. I presume this means NPTL. 
-- Fernando