diff -r 1ebc2f316e45 -r 9162feb63c42 src/hotspot/share/gc/g1/g1RemSet.cpp
--- a/src/hotspot/share/gc/g1/g1RemSet.cpp	Fri Sep 06 15:13:38 2019 +0200
+++ b/src/hotspot/share/gc/g1/g1RemSet.cpp	Fri Sep 06 13:38:55 2019 -0400
@@ -42,6 +42,7 @@
 #include "gc/g1/heapRegionRemSet.inline.hpp"
 #include "gc/g1/sparsePRT.hpp"
 #include "gc/shared/gcTraceTime.inline.hpp"
+#include "gc/shared/ptrQueue.hpp"
 #include "gc/shared/suspendibleThreadSet.hpp"
 #include "jfr/jfrEvents.hpp"
 #include "memory/iterator.hpp"
@@ -1060,7 +1061,7 @@
       _scan_state(scan_state), _ct(g1h->card_table()), _cards_dirty(0), _cards_skipped(0)
     {}
 
-    bool do_card_ptr(CardValue* card_ptr, uint worker_i) {
+    void do_card_ptr(CardValue* card_ptr, uint worker_i) {
       // The only time we care about recording cards that
       // contain references that point into the collection set
       // is during RSet updating within an evacuation pause.
@@ -1084,7 +1085,6 @@
         // regions to clear the card table at the end during the prepare() phase.
         _cards_skipped++;
       }
-      return true;
     }
 
     size_t cards_dirty() const { return _cards_dirty; }
@@ -1093,17 +1093,37 @@
 
   HeapRegionClaimer _hr_claimer;
   G1RemSetScanState* _scan_state;
+  BufferNode::Stack _dirty_card_buffers;
   bool _initial_evacuation;
 
   volatile bool _fast_reclaim_handled;
 
+  void apply_closure_to_dirty_card_buffers(G1MergeLogBufferCardsClosure* cl, uint worker_id) {
+    G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
+    size_t buffer_size = dcqs.buffer_size();
+    while (BufferNode* node = _dirty_card_buffers.pop()) {
+      cl->apply_to_buffer(node, buffer_size, worker_id);
+      dcqs.deallocate_buffer(node);
+    }
+  }
+
 public:
   G1MergeHeapRootsTask(G1RemSetScanState* scan_state, uint num_workers, bool initial_evacuation) :
     AbstractGangTask("G1 Merge Heap Roots"),
     _hr_claimer(num_workers),
     _scan_state(scan_state),
+    _dirty_card_buffers(),
     _initial_evacuation(initial_evacuation),
-    _fast_reclaim_handled(false) { }
+    _fast_reclaim_handled(false)
+  {
+    if (initial_evacuation) {
+      G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
+      G1BufferNodeList buffers = dcqs.take_all_completed_buffers();
+      if (buffers._entry_count != 0) {
+        _dirty_card_buffers.prepend(*buffers._head, *buffers._tail);
+      }
+    }
+  }
 
   virtual void work(uint worker_id) {
     G1CollectedHeap* g1h = G1CollectedHeap::heap();
@@ -1158,7 +1178,7 @@
       G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::MergeLB, worker_id);
 
       G1MergeLogBufferCardsClosure cl(g1h, _scan_state);
-      g1h->iterate_dirty_card_closure(&cl, worker_id);
+      apply_closure_to_dirty_card_buffers(&cl, worker_id);
 
       p->record_thread_work_item(G1GCPhaseTimes::MergeLB, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeLBDirtyCards);
       p->record_thread_work_item(G1GCPhaseTimes::MergeLB, worker_id, cl.cards_skipped(), G1GCPhaseTimes::MergeLBSkippedCards);