[Jack-Devel] Fwd: connecting to JACKD2 with low buffer sizes

[Christopher Obbard]

Hi Guys,

Running jack with a small buffer (-p64 -n2), and connecting with any
client causes issues.
With higher buffer sizes, all is OK.

This is on an ARM embedded system, with a single core 1MHz processor.
I've set the cpu governor to performance.

I have a custom compiled 4.14 kernel with omap2plus_defconfig with the
following config settings:
> CONFIG_PREEMPT_VOLUNTARY=y
> HZ_100=y
> CONFIG_NO_HZ_IDLE=y

$ jackd -R -P95 -dalsa -dhw:0 -r48000 -p64 -n2
> JackPosixProcessSync::LockedTimedWait error usec = 5000000 err = Connection timed out
> Driver is not running
> Cannot create new client
> CheckSize error size = 32 Size() = 12
> CheckRead error
> CheckSize error size = -1 Size() = 4
> CheckRead error
> CheckSize error size = 0 Size() = 12
> CheckRead error


Also, with higher buffer sizes sometimes I get xruns. After enabling
alsa debugging, the error is:
> ALSA: PCM: [Q] Lost interrupts?: (stream=0, delta=221, new_hw_ptr=181343, old_hw_ptr=181122)

Loosing the FIFO interrupts doesn't seem like a great thing.........


I _think_ the issue is to do with the kernel scheduling, but this why
I ask the experts :-).
Can anyone suggest any kernel settings that will improve my situation?


Many thanks,

Chris