--- old/src/hotspot/share/gc/g1/g1RemSet.hpp	2019-11-18 17:32:50.113581076 +0100
+++ new/src/hotspot/share/gc/g1/g1RemSet.hpp	2019-11-18 17:32:49.673578894 +0100
@@ -100,12 +100,13 @@
   // Prepare for and cleanup after scanning the heap roots. Must be called
   // once before and after in sequential code.
   void prepare_for_scan_heap_roots();
-  // Prepare region for scanning.
-  void prepare_region_for_scanning(HeapRegion* region);
   // Cleans the card table from temporary duplicate detection information.
   void cleanup_after_scan_heap_roots();
   // Prepares the given region for heap root scanning.
   void prepare_for_scan_heap_roots(uint region_idx);
+  // Creates a snapshot of the current _top values at the start of collection to
+  // filter out card marks that we do not want to scan.
+  void prepare_region_for_scan(HeapRegion* region);
 
   // Do work for regions in the current increment of the collection set, scanning
   // non-card based (heap) roots.