I think that the new version of Dahdi Linux complete
dahdi-linux-complete-220.127.116.11 has a bug with Dahdi dummy, i have replicated this problem on both 32bit and 64bit systems running on Ubuntu 8.04, I have tried it with asterisk 1.4 and 1.6
Dahdi compiles fine but it appears that dahdi dummy doesn’t load 100% and a process called ksoftirqd constantly uses between 20% and 30% of the processor, stopping Dahdi causes the processor to revert back to normal.
Reverting back to dahdi-linux-complete-18.104.22.168 solved the problem.
I have a number of systems running on the problematic dahdi not using dahdi dummy, i.e. Digium or Sangoma cards and they seem to not have this problem, so it only occurs with dahdi dummy.