rpc2, debugger: Fix comments around goroutine grouping (#3374)

service/debugger/debugger.go

@@ -1669,9 +1669,16 @@ func formatLoc(loc proc.Location) string {
 	return fmt.Sprintf("%s:%d in %s", loc.File, loc.Line, fnname)
 }
 
-// GroupGoroutines divides goroutines in gs into groups as specified by groupBy and groupByArg.
-// A maximum of maxGoroutinesPerGroup are saved in each group, but the total
-// number of goroutines in each group is recorded.
+// GroupGoroutines divides goroutines in gs into groups as specified by
+// group.{GroupBy,GroupByKey}. A maximum of group.MaxGroupMembers are saved in
+// each group, but the total number of goroutines in each group is recorded. If
+// group.MaxGroups is set, then at most that many groups are returned. If some
+// groups end up being dropped because of this limit, the tooManyGroups return
+// value is set.
+//
+// The first return value represents the goroutines that have been included in
+// one of the returned groups (subject to the MaxGroupMembers and MaxGroups
+// limits). The second return value represents the groups.
 func (d *Debugger) GroupGoroutines(gs []*proc.G, group *api.GoroutineGroupingOptions) ([]*proc.G, []api.GoroutineGroup, bool) {
 	if group.GroupBy == api.GoroutineFieldNone {
 		return gs, nil, false

service/rpc2/server.go

@@ -657,7 +657,7 @@ type ListGoroutinesOut struct {
 // be grouped with the specified criterion.
 // If the value of arg.GroupBy is GoroutineLabel goroutines will
 // be grouped by the value of the label with key GroupByKey.
-// For each group a maximum of MaxExamples example goroutines are
+// For each group a maximum of MaxGroupMembers example goroutines are
 // returned, as well as the total number of goroutines in the group.
 func (s *RPCServer) ListGoroutines(arg ListGoroutinesIn, out *ListGoroutinesOut) error {
 	//TODO(aarzilli): if arg contains a running goroutines filter (not negated)