This will pollute the data in the timer.  for each statsd metric that is skipped, the timer will be led to indicate that a really fast rollup occured.

I'm starting to doubt the usefulness of this timer, given that it is 1) now used by different kinds of rollup tasks and 2) can be short-cicuited.  Do you think we can get by tracking just calculation time (which is read + compute time) and and write time separately?