Help needed: VCVrack high CPU usage on Linux

Running Vcv Rack and the multi core experimental FreeRack on Windows for a while now on my HP all in one pc without problems. Now I installed both on my Mint Linux system which is quite fast 32gb ram 6 core fast cpu. Nvidia 660 graphics. Running Rack or FreeRack shows me that even mults take up about 40 to 50 ms. Had to switch to FreeRack adding additional cpus for even simple patches. Don’t think it’s gpu because resizing and zooming in Rack is much faster than on my hp windows pc and running only in a small window does not influence the high cpu consumption. Does anyone has an idea what is causing this?
Regards Dieter

To give a little bit more information. It looks like that EVERY module takes about 40mS base load without doing much, even mults.

in linux its all about proper jack, governor and realtime prio settings - i’m using vcvrack with surprisingly good results even on small arm boards with proper tuning ( here are some settings to give you a start:

  • use jack and allow realtime prio for it
  • use the “threadirq” kernel option if it works for you (on some systems jack was strangly hanging with it on other systems it works flawlessly)
  • if it works, then: systemctl stop irqbalance
  • some kernel settings (maybe google for the details):
echo never > /sys/kernel/mm/transparent_hugepage/enabled
echo 524288 > /proc/sys/fs/inotify/max_user_watches
echo 1 > /sys/module/processor/parameters/ignore_ppc
# get the max_possible_frequency from cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
for i in /sys/devices/system/cpu/cpu?/cpufreq/scaling_max_freq ; do
  echo max_possible_frequency > $i
for i in /sys/devices/system/cpu/cpu?/cpufreq/scaling_governor ; do
  echo performance > $i
chmod a+r /dev/rtc0
chmod a+r /dev/hpetsysctl -w kernel.sched_rt_runtime_us=-1
  • maybe start vcvrack with realtime prio as well: chrt 20 Rack
  • use two threads if one is not enough (more make no real sense)
  • use low screen refresh rates (for me it works well with 15hz in vcvrack)
  • lower sample rates are better than higher (32khz is better than 44.1khz is better than 48khz etc.)

i think this should give you enough things to try out … let me know if it works out for you

best wishes - hexdump