linuxaudio.org

Michael Ost wrote:

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> The higher priority threads in the system are:

> ...

> * IRQ8 (rtc) - FIFO/99

Why does this interrupt get such a high priority?

(Not that it matters as I don't expect it to be used at all ...)
> Are there issues with memory mapping, that can block other unrelated

quoted text
> threads?

Then you would have seen page faults.
> There do appear to be "involuntary context switches" (as reported by

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> getrusage) when the spikes happen. This makes it seem like the

> scheduler is interrupting our threads. But how do you figure out why

> that is happening?  [...]  All of the 5 processing threads are

> SCHED_RR/76. [...]  Are there just too danged many SCHED_RR threads

> fighting for two cores?

RR means Round Robin, i.e., all threads with the same priority get

an equal amount of CPU without much delay, so the scheduler has to

switch between them quite often.  RR is intended for threads that must

make some progress continuously.  (See "man sched_setscheduler" and

especially "man sched_rr_get_interval".)
If you want to run a thread until it has finished for now, use

SCHED_FIFO.
I assume it is your intention that all those threads have equal priority

(which means to the kernel "don't care which one of them gets executed

first").
Regards,

Clemens

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