i’m currently testing my system if it works with jackd and ardour. It uses the 2.6.19 kernel with the realtime patch rt9 on Ubuntu 6.10 on AMD64 with dual Opteron 165. After fiddling with the priorities i got jackd to run stable.
When no client is attached jackd runs very stable, even during heavy system load (scons -j 6 plus 2 glxgears plus heavy network traffic) without xruns. Jackd reports between 5us and about 60us max latency.
But with ardour2 from current SVN there are problems when starting/stopping recordings and also randomly while recording with short buffers. (fresh project, one 8 channel track)
Jackd reports xruns of up to 0.1ms without system load. With system load (2x glxgears) xruns of mostly about 0.1ms but up to 2ms just by moving the mouse on the desktop.
To my understanding this shouldn’t happen because the soundprocessing should not be influenced by other events/processes.
Is there something in ardour that is known to cause these delays?
Can it be avoided by changing some of ardours threads priorities? (Currently jackd and the soundcard IRQs have FIFO with priority 95, which is above all others but the realtime clock and migration).