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

[marcin at saepia.net]

Great! Please, could you commit the attached patch?

m.



2011/6/20 Colin Guthrie <gmane at colin.guthr.ie>:
> '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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