--- a/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Tue Oct 07 14:54:53 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Thu Oct 09 11:40:11 2014 +0200
@@ -131,7 +131,10 @@
   storage->set_mapping_changed_listener(&_listener);
 }
 
-void CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions) {
+void CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions, bool zero_filled) {
+  if (zero_filled) {
+    return;
+  }
   // We need to clear the bitmap on commit, removing any existing information.
   MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_region), num_regions * HeapRegion::GrainWords);
   _bm->clearRange(mr);

--- a/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.hpp	Tue Oct 07 14:54:53 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.hpp	Thu Oct 09 11:40:11 2014 +0200
@@ -127,7 +127,7 @@
 
   void set_bitmap(CMBitMap* bm) { _bm = bm; }
 
-  virtual void on_commit(uint start_idx, size_t num_regions);
+  virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 };
 
 class CMBitMap : public CMBitMapRO {

--- a/hotspot/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp	Tue Oct 07 14:54:53 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp	Thu Oct 09 11:40:11 2014 +0200
@@ -109,7 +109,7 @@
 
 class G1BlockOffsetSharedArrayMappingChangedListener : public G1MappingChangedListener {
  public:
-  virtual void on_commit(uint start_idx, size_t num_regions) {
+  virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
     // Nothing to do. The BOT is hard-wired to be part of the HeapRegion, and we cannot
     // retrieve it here since this would cause firing of several asserts. The code
     // executed after commit of a region already needs to do some re-initialization of

--- a/hotspot/src/share/vm/gc_implementation/g1/g1CardCounts.cpp	Tue Oct 07 14:54:53 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CardCounts.cpp	Thu Oct 09 11:40:11 2014 +0200
@@ -33,7 +33,10 @@
 
 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
 
-void G1CardCountsMappingChangedListener::on_commit(uint start_idx, size_t num_regions) {
+void G1CardCountsMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
+  if (zero_filled) {
+    return;
+  }
   MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_idx), num_regions * HeapRegion::GrainWords);
   _counts->clear_range(mr);
 }

--- a/hotspot/src/share/vm/gc_implementation/g1/g1CardCounts.hpp	Tue Oct 07 14:54:53 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CardCounts.hpp	Thu Oct 09 11:40:11 2014 +0200
@@ -42,7 +42,7 @@
  public:
   void set_cardcounts(G1CardCounts* counts) { _counts = counts; }
 
-  virtual void on_commit(uint start_idx, size_t num_regions);
+  virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 };
 
 // Table to track the number of times a card has been refined. Once

--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Tue Oct 07 14:54:53 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Thu Oct 09 11:40:11 2014 +0200
@@ -389,7 +389,9 @@
   OtherRegionsTable::invalidate(start_idx, num_regions);
 }
 
-void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions) {
+void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
+  // The from card cache is not the memory that is actually committed. So we cannot
+  // take advantage of the zero_filled parameter.
   reset_from_card_cache(start_idx, num_regions);
 }
 

--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Tue Oct 07 14:54:53 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Thu Oct 09 11:40:11 2014 +0200
@@ -172,7 +172,7 @@
  private:
   void reset_from_card_cache(uint start_idx, size_t num_regions);
  public:
-  virtual void on_commit(uint start_idx, size_t num_regions);
+  virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 };
 
 class G1CollectedHeap : public SharedHeap {

--- a/hotspot/src/share/vm/gc_implementation/g1/g1RegionToSpaceMapper.cpp	Tue Oct 07 14:54:53 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1RegionToSpaceMapper.cpp	Thu Oct 09 11:40:11 2014 +0200
@@ -69,7 +69,7 @@
   virtual void commit_regions(uintptr_t start_idx, size_t num_regions) {
     _storage.commit(start_idx * _pages_per_region, num_regions * _pages_per_region);
     _commit_map.set_range(start_idx, start_idx + num_regions);
-    fire_on_commit(start_idx, num_regions);
+    fire_on_commit(start_idx, num_regions, true);
   }
 
   virtual void uncommit_regions(uintptr_t start_idx, size_t num_regions) {
@@ -115,12 +115,14 @@
       assert(!_commit_map.at(i), err_msg("Trying to commit storage at region "INTPTR_FORMAT" that is already committed", i));
       uintptr_t idx = region_idx_to_page_idx(i);
       uint old_refcount = _refcounts.get_by_index(idx);
+      bool zero_filled = false;
       if (old_refcount == 0) {
         _storage.commit(idx, 1);
+        zero_filled = true;
       }
       _refcounts.set_by_index(idx, old_refcount + 1);
       _commit_map.set_bit(i);
-      fire_on_commit(i, 1);
+      fire_on_commit(i, 1, zero_filled);
     }
   }
 
@@ -139,9 +141,9 @@
   }
 };
 
-void G1RegionToSpaceMapper::fire_on_commit(uint start_idx, size_t num_regions) {
+void G1RegionToSpaceMapper::fire_on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
   if (_listener != NULL) {
-    _listener->on_commit(start_idx, num_regions);
+    _listener->on_commit(start_idx, num_regions, zero_filled);
   }
 }
 

--- a/hotspot/src/share/vm/gc_implementation/g1/g1RegionToSpaceMapper.hpp	Tue Oct 07 14:54:53 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1RegionToSpaceMapper.hpp	Thu Oct 09 11:40:11 2014 +0200
@@ -33,7 +33,9 @@
  public:
   // Fired after commit of the memory, i.e. the memory this listener is registered
   // for can be accessed.
-  virtual void on_commit(uint start_idx, size_t num_regions) = 0;
+  // Zero_filled indicates that the memory can be considered as filled with zero bytes
+  // when called.
+  virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled) = 0;
 };
 
 // Maps region based commit/uncommit requests to the underlying page sized virtual
@@ -51,7 +53,7 @@
 
   G1RegionToSpaceMapper(ReservedSpace rs, size_t commit_granularity, size_t region_granularity, MemoryType type);
 
-  void fire_on_commit(uint start_idx, size_t num_regions);
+  void fire_on_commit(uint start_idx, size_t num_regions, bool zero_filled);
  public:
   MemRegion reserved() { return _storage.reserved(); }
 

--- a/hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp	Tue Oct 07 14:54:53 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp	Thu Oct 09 11:40:11 2014 +0200
@@ -125,7 +125,8 @@
 }
 #endif
 
-void G1SATBCardTableLoggingModRefBSChangedListener::on_commit(uint start_idx, size_t num_regions) {
+void G1SATBCardTableLoggingModRefBSChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
+  // Default value for a clean card on the card table is -1. So we cannot take advantage of the zero_filled parameter.
   MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_idx), num_regions * HeapRegion::GrainWords);
   _card_table->clear(mr);
 }

--- a/hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.hpp	Tue Oct 07 14:54:53 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.hpp	Thu Oct 09 11:40:11 2014 +0200
@@ -136,7 +136,7 @@
 
   void set_card_table(G1SATBCardTableLoggingModRefBS* card_table) { _card_table = card_table; }
 
-  virtual void on_commit(uint start_idx, size_t num_regions);
+  virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 };
 
 // Adds card-table logging to the post-barrier.