--- old/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	2020-07-15 16:23:40.831745918 +0800
+++ new/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	2020-07-15 16:23:40.567745909 +0800
@@ -89,6 +89,7 @@
 #include "logging/log.hpp"
 #include "memory/allocation.hpp"
 #include "memory/iterator.hpp"
+#include "memory/heapInspection.hpp"
 #include "memory/resourceArea.hpp"
 #include "memory/universe.hpp"
 #include "oops/access.inline.hpp"
@@ -161,9 +162,13 @@
   reset_from_card_cache(start_idx, num_regions);
 }
 
-Tickspan G1CollectedHeap::run_task(AbstractGangTask* task) {
-  Ticks start = Ticks::now();
+void G1CollectedHeap::run_task(AbstractGangTask* task) {
   workers()->run_task(task, workers()->active_workers());
+}
+
+Tickspan G1CollectedHeap::run_task_timed(AbstractGangTask* task) {
+  Ticks start = Ticks::now();
+  run_task(task);
   return Ticks::now() - start;
 }
 
@@ -3700,7 +3705,7 @@
 
   {
     G1PrepareEvacuationTask g1_prep_task(this);
-    Tickspan task_time = run_task(&g1_prep_task);
+    Tickspan task_time = run_task_timed(&g1_prep_task);
 
     phase_times()->record_register_regions(task_time.seconds() * 1000.0,
                                            g1_prep_task.humongous_total(),
@@ -3850,7 +3855,7 @@
   {
     G1RootProcessor root_processor(this, num_workers);
     G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers);
-    task_time = run_task(&g1_par_task);
+    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.
@@ -3889,7 +3894,7 @@
   {
     G1MarkScope code_mark_scope;
     G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
-    task_time = run_task(&task);
+    task_time = run_task_timed(&task);
     // See comment in evacuate_collection_set() for the reason of the scope.
   }
   Tickspan total_processing = Ticks::now() - start_processing;
@@ -4916,3 +4921,27 @@
 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
   return _g1mm->memory_pools();
 }
+
+class G1ParallelObjectIterator : public ParallelObjectIterator {
+private:
+  G1CollectedHeap*  _heap;
+  HeapRegionClaimer _claimer;
+
+public:
+  G1ParallelObjectIterator(uint thread_num) :
+      _heap(G1CollectedHeap::heap()),
+      _claimer(thread_num == 0 ? G1CollectedHeap::heap()->workers()->active_workers() : thread_num) {}
+
+  virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
+    _heap->object_iterate_parallel(cl, worker_id, &_claimer);
+  }
+};
+
+ParallelObjectIterator* G1CollectedHeap::parallel_object_iterator(uint thread_num) {
+  return new G1ParallelObjectIterator(thread_num);
+}
+
+void G1CollectedHeap::object_iterate_parallel(ObjectClosure* cl, uint worker_id, HeapRegionClaimer* claimer) {
+  IterateObjectClosureRegionClosure blk(cl);
+  heap_region_par_iterate_from_worker_offset(&blk, claimer, worker_id);
+}