[LAU] Crackles in audio - how to troubleshoot ?

[jonetsu at teksavvy.com]

Hello,

Suddenly the audio started crackling.  I was listening to a youtube
tutorial (firefox) and it started.  Bitwig and Renoise were running but
not playing anything.  I looked at  the log files (syslog, kern) nothing
relevant.  Card is 10101LT.

jackd runs at about 10.3ms latency (last time I checked using
jack_iodelay), so it run as:

/usr/bin/jackd --sync -T -P95 -ndefault -dalsa -dhw:M1010LT -r44100
-p128 -n2

scaling_gouvernor all set to performance.  Interrupt prio looks OK:

  PID CLS RTPRIO  NI PRI %CPU STAT COMMAND
  436 FF      90   - 130  1.6 S    irq/18-snd_ice1
   47 FF      50   -  90  0.0 S    irq/9-acpi

limits audio.conf is:

@audio   -  rtprio     95
@audio   -  memlock    unlimited

Interrupts servicing for all 4 CPUs (i5) :

  0:  IR-IO-APIC-edge      i8042
  4:  IR-IO-APIC-edge    
  8:  IR-IO-APIC-edge      rtc0
  9:  IR-IO-APIC-fasteoi   acpi
 12:  IR-IO-APIC-edge      i8042
 18:  IR-IO-APIC-fasteoi   snd_ice1712

jackd and pulse processes:

 /usr/bin/pulseaudio --start --log-target=syslog

 [pulseaudio] <defunct>

 /usr/bin/jackd -T -ndefault --sync -T -P95 -ndefault -dalsa
 -dhw:M1010LT -r44100 -p128 -n2

The pa zombie was there way before the crackling started.  Not sure if
this is related.

The pulseaudio jackd sink is active and can be seen in qjackctl.

So it seems OK.  But the audio is full of crackles.  In firefox, as
well as Bitwig and Renoise when now something is played.  Of course,
when the machine was started some audio was played in both Bitwig and
Renoise and it was fine.  Then I watched a youtube tutorial and bam,
after maybe 15 minutes, all audio output is full of crackling.

Since the log files shows nothing.  How is troubleshooting information
gathered ?  There should be some SW system component that can be
probed, somwthing that could be observed.  - or is it that the 1010LT
is going awry ?  Can this happen at all ?

Thanks for suggestions and comments !

Cheers.