8272235: G1: update outdated code root fixup

Reviewed-by: tschatzl, kbarrett

src/hotspot/share/gc/g1/g1CollectedHeap.cpp

@@ -3713,14 +3713,16 @@ void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* p
                                       num_workers,
                                       has_optional_evacuation_work);
     task_time = run_task_timed(&g1_par_task);
-    // Closing the inner scope will execute the destructor for the G1RootProcessor object.
-    // To extract its code root fixup time we measure total time of this scope and
-    // subtract from the time the WorkGang task took.
+    // Closing the inner scope will execute the destructor for the
+    // G1RootProcessor object. By subtracting the WorkGang task from the total
+    // time of this scope, we get the "NMethod List Cleanup" time. This list is
+    // constructed during "STW two-phase nmethod root processing", see more in
+    // nmethod.hpp
   }
   Tickspan total_processing = Ticks::now() - start_processing;
 
   p->record_initial_evac_time(task_time.seconds() * 1000.0);
-  p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
+  p->record_or_add_nmethod_list_cleanup_time((total_processing - task_time).seconds() * 1000.0);
 
   rem_set()->complete_evac_phase(has_optional_evacuation_work);
 }
@@ -3745,6 +3747,7 @@ public:
 };
 
 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) {
+  // To access the protected constructor/destructor
   class G1MarkScope : public MarkScope { };
 
   Tickspan task_time;
@@ -3754,12 +3757,12 @@ void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* pe
     G1MarkScope code_mark_scope;
     G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
     task_time = run_task_timed(&task);
-    // See comment in evacuate_collection_set() for the reason of the scope.
+    // See comment in evacuate_initial_collection_set() for the reason of the scope.
   }
   Tickspan total_processing = Ticks::now() - start_processing;
 
   G1GCPhaseTimes* p = phase_times();
-  p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
+  p->record_or_add_nmethod_list_cleanup_time((total_processing - task_time).seconds() * 1000.0);
 }
 
 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {

src/hotspot/share/gc/g1/g1GCPhaseTimes.cpp

@@ -154,7 +154,7 @@ G1GCPhaseTimes::G1GCPhaseTimes(STWGCTimer* gc_timer, uint max_gc_threads) :
 void G1GCPhaseTimes::reset() {
   _cur_collection_initial_evac_time_ms = 0.0;
   _cur_optional_evac_time_ms = 0.0;
-  _cur_collection_code_root_fixup_time_ms = 0.0;
+  _cur_collection_nmethod_list_cleanup_time_ms = 0.0;
   _cur_merge_heap_roots_time_ms = 0.0;
   _cur_optional_merge_heap_roots_time_ms = 0.0;
   _cur_prepare_merge_heap_roots_time_ms = 0.0;
@@ -448,7 +448,7 @@ double G1GCPhaseTimes::print_evacuate_initial_collection_set() const {
 }
 
 double G1GCPhaseTimes::print_post_evacuate_collection_set() const {
-  const double sum_ms = _cur_collection_code_root_fixup_time_ms +
+  const double sum_ms = _cur_collection_nmethod_list_cleanup_time_ms +
                         _recorded_preserve_cm_referents_time_ms +
                         _cur_ref_proc_time_ms +
                         (_weak_phase_times.total_time_sec() * MILLIUNITS) +
@@ -461,7 +461,7 @@ double G1GCPhaseTimes::print_post_evacuate_collection_set() const {
 
   info_time("Post Evacuate Collection Set", sum_ms);
 
-  debug_time("Code Roots Fixup", _cur_collection_code_root_fixup_time_ms);
+  debug_time("NMethod List Cleanup", _cur_collection_nmethod_list_cleanup_time_ms);
 
   debug_time_for_reference("Reference Processing", _cur_ref_proc_time_ms);
   _ref_phase_times.print_all_references(2, false);

src/hotspot/share/gc/g1/g1GCPhaseTimes.hpp

@@ -154,7 +154,7 @@ class G1GCPhaseTimes : public CHeapObj<mtGC> {
 
   double _cur_collection_initial_evac_time_ms;
   double _cur_optional_evac_time_ms;
-  double _cur_collection_code_root_fixup_time_ms;
+  double _cur_collection_nmethod_list_cleanup_time_ms;
 
   double _cur_merge_heap_roots_time_ms;
   double _cur_optional_merge_heap_roots_time_ms;
@@ -283,8 +283,8 @@ class G1GCPhaseTimes : public CHeapObj<mtGC> {
     _cur_optional_evac_time_ms += ms;
   }
 
-  void record_or_add_code_root_fixup_time(double ms) {
-    _cur_collection_code_root_fixup_time_ms += ms;
+  void record_or_add_nmethod_list_cleanup_time(double ms) {
+    _cur_collection_nmethod_list_cleanup_time_ms += ms;
   }
 
   void record_merge_heap_roots_time(double ms) {

test/hotspot/jtreg/gc/g1/TestGCLogMessages.java

@@ -156,6 +156,10 @@ public class TestGCLogMessages {
         // TLAB handling
         new LogMessageWithLevel("Prepare TLABs", Level.DEBUG),
         new LogMessageWithLevel("Resize TLABs", Level.DEBUG),
+
+        // NMethod List Cleanup
+        new LogMessageWithLevel("NMethod List Cleanup", Level.DEBUG),
+
         // Reference Processing
         new LogMessageWithLevel("Reference Processing", Level.DEBUG),
         // VM internal reference processing