Specify the default metric by which the function list is sorted. The sort metric is the first metric in this list that matches a metric in any loaded experiment, subject to the following conditions:
If the entry in metric-spec has a visibility string of an exclamation point, !, the first metric whose name matches is used, regardless of whether it is visible.
If the entry in metric-spec has any other visibility string, the first visible metric whose name matches is used.
The syntax and use of the metric list is described in the section Metric Lists.
The default sort metric for the Callers-Callees list is the attributed metric corresponding to the default sort metric for the function list.