
CheckController is critical for speed

parse jobs: 1.5 usec per job + 20 usec

check exit stack: 2.7ms average, up to 10ms: this seems to be the
kernel scheduler putting pcontrol in the background every now and
again.  

with 1024 jobs and 4 machines, the jobs being sent to machines (should
take only 1 second, but timeouts add in delays) takes up the first few
seconds.  initially


*write this up, add some tests for timing... *
