--- a/src/hotspot/share/gc/g1/g1SATBMarkQueueSet.cpp	Tue Aug 14 10:42:00 2018 +0800
+++ b/src/hotspot/share/gc/g1/g1SATBMarkQueueSet.cpp	Tue Aug 14 00:15:56 2018 -0400
@@ -23,8 +23,24 @@
  */
 
 #include "precompiled.hpp"
+#include "gc/g1/g1CollectedHeap.inline.hpp"
 #include "gc/g1/g1SATBMarkQueueSet.hpp"
 #include "gc/g1/g1ThreadLocalData.hpp"
+#include "gc/g1/heapRegion.hpp"
+#include "gc/g1/satbMarkQueue.hpp"
+#include "oops/oop.hpp"
+#include "utilities/debug.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+G1SATBMarkQueueSet::G1SATBMarkQueueSet() : _g1h(NULL) {}
+
+void G1SATBMarkQueueSet::initialize(G1CollectedHeap* g1h,
+                                    Monitor* cbl_mon, Mutex* fl_lock,
+                                    int process_completed_threshold,
+                                    Mutex* lock) {
+  SATBMarkQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, lock);
+  _g1h = g1h;
+}
 
 void G1SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
   G1ThreadLocalData::satb_mark_queue(t).handle_zero_index();
@@ -33,3 +49,77 @@
 SATBMarkQueue& G1SATBMarkQueueSet::satb_queue_for_thread(JavaThread* const t) const{
   return G1ThreadLocalData::satb_mark_queue(t);
 }
+
+// Return true if a SATB buffer entry refers to an object that
+// requires marking.
+//
+// The entry must point into the G1 heap.  In particular, it must not
+// be a NULL pointer.  NULL pointers are pre-filtered and never
+// inserted into a SATB buffer.
+//
+// An entry that is below the NTAMS pointer for the containing heap
+// region requires marking. Such an entry must point to a valid object.
+//
+// An entry that is at least the NTAMS pointer for the containing heap
+// region might be any of the following, none of which should be marked.
+//
+// * A reference to an object allocated since marking started.
+//   According to SATB, such objects are implicitly kept live and do
+//   not need to be dealt with via SATB buffer processing.
+//
+// * A reference to a young generation object. Young objects are
+//   handled separately and are not marked by concurrent marking.
+//
+// * A stale reference to a young generation object. If a young
+//   generation object reference is recorded and not filtered out
+//   before being moved by a young collection, the reference becomes
+//   stale.
+//
+// * A stale reference to an eagerly reclaimed humongous object.  If a
+//   humongous object is recorded and then reclaimed, the reference
+//   becomes stale.
+//
+// The stale reference cases are implicitly handled by the NTAMS
+// comparison. Because of the possibility of stale references, buffer
+// processing must be somewhat circumspect and not assume entries
+// in an unfiltered buffer refer to valid objects.
+
+static inline bool requires_marking(const void* entry, G1CollectedHeap* g1h) {
+  // Includes rejection of NULL pointers.
+  assert(g1h->is_in_reserved(entry),
+         "Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry));
+
+  HeapRegion* region = g1h->heap_region_containing(entry);
+  assert(region != NULL, "No region for " PTR_FORMAT, p2i(entry));
+  if (entry >= region->next_top_at_mark_start()) {
+    return false;
+  }
+
+  assert(oopDesc::is_oop(oop(entry), true /* ignore mark word */),
+         "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry));
+
+  return true;
+}
+
+static inline bool discard_entry(const void* entry, G1CollectedHeap* g1h) {
+  return !requires_marking(entry, g1h) || g1h->is_marked_next((oop)entry);
+}
+
+// Workaround for not yet having std::bind.
+class G1SATBMarkQueueFilterFn {
+  G1CollectedHeap* _g1h;
+
+public:
+  G1SATBMarkQueueFilterFn(G1CollectedHeap* g1h) : _g1h(g1h) {}
+
+  // Return true if entry should be filtered out (removed), false if
+  // it should be retained.
+  bool operator()(const void* entry) const {
+    return discard_entry(entry, _g1h);
+  }
+};
+
+void G1SATBMarkQueueSet::filter(SATBMarkQueue* queue) {
+  assert(_g1h != NULL, "SATB queue set not initialized");
+  apply_filter(G1SATBMarkQueueFilterFn(_g1h), queue);
+}