Add new performance counters

[hkaiser]

I think we should add counters for what I called phase duration and task length in my paper. Right now we have idle_rate = 1-(exec_total/tfunc_total) * 10000 [.01%]:

phase_duration = exec_total / cumulative_phases [ns]
task_length = exec_total / phases [ns]

so the flags for cumulative counts and idle_rate would both have to be turned on for this to work

Also, I’m wondering if we should be able to reset certain counters for intervals. I’m thinking that if I measure these on an interval basis right now it would be accumulative and it would be useful to reset them for that interval. This would be something we can consider and do later if it is feasible.

[hkaiser]

That has been fixed by merging #1289