JACK and ZynAddSubFX Survive Intense Thrashing!
I wrote a program with a serious memory leak, and filled up my 512MB RAM and 1GB swap. My computer, falcon, was in serious thrashing mode. The red led was on solid, X was completely unresponsive (characters I typed in my xterm showed up about 10 minutes later). Even my laptop's network connection was unresponsive (because falcon is my router here)
While I was debating as to why the Out-Of-Memory killer hadn't reaped my runaway process yet, I got curious as to whether JACK would work at all. So I reached over and pressed some keys on my MIDI keyboard (ZynAddSubFX was running, as it usually is), and sure enough Zyn came sounding through loud and clear. In fact, I couldn't hear a single XRUN. It was as if the computer was as idle as could be. I was seriously impressed.
Impressed, but not overly surprised. I did ask for this after all. I have
2.6.13 with Ingo Molnar's realtime-preempt patch, and rtlimits configured
properly. jackd runs at priority 65, and my sound card at priority 99. I have
the realtime-preempt patch configured at PREEMPT_DESKTOP, because I've had
stability issues with PREEMPT_RT. PREEMPT_DESKTOP has been solid though, I
have a 33-day uptime, and I use falcon heavily.
I won't go into the details again on how to get where I am, because the information in the last paragraph coupled with tapas' excellent instructions for realtime preemption and rtlimits are all you need.
One last statistic, in case you still don't believe me. That thrashing session started about an hour ago and lasted about half an hour. Here's the screenshot from qjackctl:
