the shared file time_by_slowest metric doesn't distinguish metadata and i/o time
Reported by Huong Luu.
This is the most accurate metric for estimating performance for globally shared files, but it lumps both metadata and I/O transfer into the same measurement.
Ideally we would break down the two categories to help with analysis. This would require a library change, log format change, and utility change. The current log file does not contain this level of detail.