--- old/src/hotspot/share/gc/g1/g1RemSet.cpp	2019-11-20 14:56:57.826667540 +0100
+++ new/src/hotspot/share/gc/g1/g1RemSet.cpp	2019-11-20 14:56:57.484656955 +0100
@@ -927,6 +927,8 @@
     uint _merged_fine;
     uint _merged_coarse;
 
+    size_t _cards_dirty;
+
     // Returns if the region contains cards we need to scan. If so, remember that
     // region in the current set of dirty regions.
     bool remember_if_interesting(uint const region_idx) {
@@ -942,7 +944,8 @@
       _ct(G1CollectedHeap::heap()->card_table()),
       _merged_sparse(0),
       _merged_fine(0),
-      _merged_coarse(0) { }
+      _merged_coarse(0),
+      _cards_dirty(0) { }
 
     void next_coarse_prt(uint const region_idx) {
       if (!remember_if_interesting(region_idx)) {
@@ -952,7 +955,7 @@
       _merged_coarse++;
 
       size_t region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion;
-      _ct->mark_region_dirty(region_base_idx, HeapRegion::CardsPerRegion);
+      _cards_dirty += _ct->mark_region_dirty(region_base_idx, HeapRegion::CardsPerRegion);
       _scan_state->set_chunk_region_dirty(region_base_idx);
     }
 
@@ -966,7 +969,7 @@
       size_t const region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion;
       BitMap::idx_t cur = bm->get_next_one_offset(0);
       while (cur != bm->size()) {
-        _ct->mark_clean_as_dirty(region_base_idx + cur);
+        _cards_dirty += _ct->mark_clean_as_dirty(region_base_idx + cur);
         _scan_state->set_chunk_dirty(region_base_idx + cur);
         cur = bm->get_next_one_offset(cur + 1);
       }
@@ -982,7 +985,7 @@
       size_t const region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion;
       for (uint i = 0; i < num_cards; i++) {
         size_t card_idx = region_base_idx + cards[i];
-        _ct->mark_clean_as_dirty(card_idx);
+        _cards_dirty += _ct->mark_clean_as_dirty(card_idx);
         _scan_state->set_chunk_dirty(card_idx);
       }
     }
@@ -1001,6 +1004,8 @@
     size_t merged_sparse() const { return _merged_sparse; }
     size_t merged_fine() const { return _merged_fine; }
     size_t merged_coarse() const { return _merged_coarse; }
+
+    size_t cards_dirty() const { return _cards_dirty; }
   };
 
   // Visitor for the remembered sets of humongous candidate regions to merge their
@@ -1046,6 +1051,8 @@
     size_t merged_sparse() const { return _cl.merged_sparse(); }
     size_t merged_fine() const { return _cl.merged_fine(); }
     size_t merged_coarse() const { return _cl.merged_coarse(); }
+
+    size_t cards_dirty() const { return _cl.cards_dirty(); }
   };
 
   // Visitor for the log buffer entries to merge them into the card table.
@@ -1147,6 +1154,7 @@
       p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_sparse(), G1GCPhaseTimes::MergeRSMergedSparse);
       p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_fine(), G1GCPhaseTimes::MergeRSMergedFine);
       p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_coarse(), G1GCPhaseTimes::MergeRSMergedCoarse);
+      p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeRSDirtyCards);
     }
 
     // Merge remembered sets of current candidates.
@@ -1158,6 +1166,7 @@
       p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_sparse(), G1GCPhaseTimes::MergeRSMergedSparse);
       p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_fine(), G1GCPhaseTimes::MergeRSMergedFine);
       p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_coarse(), G1GCPhaseTimes::MergeRSMergedCoarse);
+      p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeRSDirtyCards);
     }
 
     // Apply closure to log entries in the HCC.