Am having problems with nasty pops/glitches every 2-3 seconds running low-ish latency audio code on my Pi 3.
Pi 3, CPU scaling set to performance on all cores
Behringer UMA25s audio/midi interface (it's cheap, class-compliant, has audio+midi+keys+faders, and runs off batteries)
jackd2 using ALSA backend, headless mode, priority = 89 (can run it at 99 as root if need be), 3 buffers, 128 or 256 samples (running at 256 for now)
Portaudio v19 configured for jack
Raspbian jessie lite, with the various additional packages required for jack.
I've checked my portaudio code with an accurate timer - each callback cycle is reliably completing in 3000us or less. There aren't any syscalls, locks etc in my code which could potentially cause dropouts.
I've switched off the services listed on Jeremy's wiki page (haven't tried disabling wifi, which I suspect may be a culprit, though my Pi is running on a wired LAN anyway).
The 256-sample buffers I'm running are equivalent to 5800us at 44.1KHz, so the processing window ought in theory to be maybe 4500us max, assuming max. 75% system load.
Most of the time it's OK, with no XRUNs reported, but every second or two I get loud pops/clicks/dropouts.
Any suggestions as to what to look for? Make sure Wi-Fi is fully disabled? Try a different USB audio device? Something else?