linuxaudio.org

On Thu, 18.06.09 14:49, Paul Davis (paul@linuxaudiosystems.com) wrote:
> > So, to map this to JACK, I would prefer if jack_cycle_wait() would

quoted text
> > also exist in a non-blocking variant. i.e. something that can return 0

> > if there's nothing to process, but doesn't necessarily wait.

>

> that's not possible. the thread has to be ready to respond to the

> start of the JACK process cycle with RT-friendly timing.

> thats why "do_my_other_work_if_there_is_any()" is still under RT

> constraints *AND* needs to be designed knowing that

> it may be stealing processor time from other parts of the process

> cycle.

In PA's ALSA module we use snd_pcm_avail() for this: only if it is

below a certain threshold we process those private events. If it is

not, then we go back to IO directly, assuming that it is too risky

trying to dispatch another event.
On Jack we have jack_frames_since_cycle_start(), would it be

considered an ugly hack if I use that to implement a similar logic?
for (;;) {

    n = jack_client_wait()

    process(n);

    jack_cycle_signal();

    while (jack_frames_since_cycle_start() < threshold)

        process_one_of_my_private_event();

}
Just ugly? Or *too* ugly? Is jack_frames_since_cycle_start() costly?
Lennart
--

Lennart Poettering                        Red Hat, Inc.

lennart [at] poettering [dot] net

http://0pointer.net/lennart/           GnuPG 0x1A015CC4

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