[pulseaudio-discuss] Why only selected modules try to acquire realtime priority?

[Colin Guthrie]

'Twas brillig, and marcin at saepia.net at 20/06/11 14:55 did gyre and gimble:
> Hi,
> 
> I am trying to figure out why PulseAudio daemon drops a few samples
> from time to time.
> 
> I got a few null sinks combined with each other by loopbacks. Then my
> applications gather sound from their .monitors. Sounds simple.
> 
> I quickly came to idea that running PulseAudio in RT mode could help.
> I encountered a lot of problems, because:
> - my PA daemons are started at the boot time (but as normal users!)
> and start-stop-daemon know nothing about /etc/security/limits.conf, so
> I got troubles with setting limits for them without setting RT limits
> for the whole system,
> - PA daemon tries to communicate to rtkit and rtkit tries to
> communicate to PolicyKit which becomes the next dependency for me
> etc...
> 
> During the process I started to investigate pulseaudio & rtkit source
> code and I found something strange.
> 
> e.g. combine module tries to acquire realtime priority during thread
> initialization:
> 
> static void thread_func(void *userdata) {
>     struct userdata *u = userdata;
> 
>     pa_assert(u);
> 
>     pa_log_debug("Thread starting up");
> 
>     if (u->core->realtime_scheduling)
>         pa_make_realtime(u->core->realtime_priority+1);
> 
>     pa_thread_mq_install(&u->thread_mq);
> 
> 
> while e.g. NULL sink doesn't:
> 
> static void thread_func(void *userdata) {
>     struct userdata *u = userdata;
> 
>     pa_assert(u);
> 
>     pa_log_debug("Thread starting up");
> 
>     pa_thread_mq_install(&u->thread_mq);
> 
> 
> 
> What is the reason for that?
> 
> For me, it means that even if I solve all problems mentioned above, my
> NULL sinks still wouldn't be using realtime scheduler policy?
> 
> Shouldn't it be fixed?

Probably this is just because no one has had a reason for this
before.... it's certainly worth thinking about if it does solve your
problem.

Col



-- 

Colin Guthrie
gmane(at)colin.guthr.ie
http://colin.guthr.ie/

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