8349836: G1: Improve group prediction log message

Reviewed-by: ayang, iwalulya

Author: Thomas Schatzl

src/hotspot/share/gc/g1/g1CollectionSetCandidates.cpp

@@ -102,19 +102,23 @@ double G1CSetCandidateGroup::predict_group_total_time_ms() const {
   double merge_scan_time_ms = p->predict_merge_scan_time(card_rs_length);
   double non_young_other_time_ms = p->predict_non_young_other_time_ms(length());
 
-  log_trace(gc, ergo, cset) ("Prediction for group with %u regions, card_rs_length %zu, merge_scan_time %.2fms, code_root_scan_time_ms %.2fms, evac_time_ms %.2fms, other_time %.2fms, bytes_to_cop %zu",
+  double total_time_ms = merge_scan_time_ms +
+                         predict_code_root_scan_time_ms +
+                         predicted_copy_time_ms +
+                         non_young_other_time_ms;
+
+  log_trace(gc, ergo, cset) ("Prediction for group %u (%u regions): total_time %.2fms card_rs_length %zu merge_scan_time %.2fms code_root_scan_time_ms %.2fms evac_time_ms %.2fms other_time %.2fms bytes_to_copy %zu",
+                             group_id(),
                              length(),
+                             total_time_ms,
                              card_rs_length,
                              merge_scan_time_ms,
                              predict_code_root_scan_time_ms,
                              predicted_copy_time_ms,
                              non_young_other_time_ms,
                              predict_bytes_to_copy);
 
-  return merge_scan_time_ms +
-         predict_code_root_scan_time_ms +
-         predicted_copy_time_ms +
-         non_young_other_time_ms;
+  return total_time_ms;
 }
 
 int G1CSetCandidateGroup::compare_gc_efficiency(G1CSetCandidateGroup** gr1, G1CSetCandidateGroup** gr2) {