It would be valuable to measure cpu time consumed by an operation, both as it's running and rolled up by user (to measure resource consumption by a particular user). We could potentially expose this via currentOp, via server status metrics or perhaps in a custom agg pipeline (if by user).

On linux pthread_getcpuclockid() offers a way to access cpu time consumed by a particular thread relatively easily. In turn, we could capture time at opCtx creation, then store the delta on each call to opCtx->checkForInterrupt, then flush the final value into the user level roll up at opCtx destruction.