--- old/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	2020-04-25 20:53:28.723348913 +0800
+++ new/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	2020-04-25 20:53:28.559349414 +0800
@@ -87,6 +87,7 @@
 #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"
@@ -4978,3 +4979,27 @@
 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);
+}