--- a/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp	Thu Dec 18 13:59:59 2008 -0800
+++ b/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp	Fri Dec 19 12:15:34 2008 -0800
@@ -726,7 +726,7 @@
   size_t live_to_left = bitmap->live_words_in_range(search_start, oop(addr));
 
   result += partial_obj_size + live_to_left;
-  assert(result <= addr, "object cannot move to the right");
+  DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result);)
   return result;
 }
 
@@ -1473,8 +1473,52 @@
 }
 
 void
+PSParallelCompact::provoke_split_fill_survivor(SpaceId id)
+{
+  if (total_invocations() % (ParallelOldGCSplitInterval * 3) != 0) {
+    return;
+  }
+
+  MutableSpace* const space = _space_info[id].space();
+  if (space->is_empty()) {
+    HeapWord* b = space->bottom();
+    HeapWord* t = b + space->capacity_in_words() / 2;
+    space->set_top(t);
+    if (ZapUnusedHeapArea) {
+      space->set_top_for_allocations();
+    }
+
+    size_t obj_len = 8;
+    while (b + obj_len <= t) {
+      CollectedHeap::fill_with_object(b, obj_len);
+      mark_bitmap()->mark_obj(b, obj_len);
+      summary_data().add_obj(b, obj_len);
+      b += obj_len;
+      obj_len = (obj_len & 0x18) + 8; // 8 16 24 32 8 16 24 32 ...
+    }
+    if (b < t) {
+      // The loop didn't completely fill to t (top); adjust top downward.
+      space->set_top(b);
+      if (ZapUnusedHeapArea) {
+        space->set_top_for_allocations();
+      }
+    }
+
+    HeapWord** nta = _space_info[id].new_top_addr();
+    bool result = summary_data().summarize(_space_info[id].split_info(),
+                                           space->bottom(), space->top(), NULL,
+                                           space->bottom(), space->end(), nta);
+    assert(result, "space must fit into itself");
+  }
+}
+
+void
 PSParallelCompact::provoke_split(bool & max_compaction)
 {
+  if (total_invocations() % ParallelOldGCSplitInterval != 0) {
+    return;
+  }
+
   const size_t region_size = ParallelCompactData::RegionSize;
   ParallelCompactData& sd = summary_data();
 
@@ -1587,6 +1631,12 @@
     assert(result, "space must fit into itself");
     _space_info[i].set_dense_prefix(space->bottom());
   }
+
+#ifndef PRODUCT
+  if (ParallelOldGCSplitALot) {
+    provoke_split_fill_survivor(to_space_id);
+  }
+#endif // #ifndef PRODUCT
 }
 
 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
@@ -1794,9 +1844,7 @@
   }
 #ifndef PRODUCT
   if (ParallelOldGCSplitALot && old_space_total_live < old_capacity) {
-    if (total_invocations() % ParallelOldGCSplitInterval == 0) {
-      provoke_split(maximum_compaction);
-    }
+    provoke_split(maximum_compaction);
   }
 #endif // #ifndef PRODUCT
 
@@ -1828,14 +1876,6 @@
                                           new_top_addr);
       assert(done, "space must fit into old gen");
 
-      // XXX - this is necessary because decrement_destination_counts() tests
-      // source_region() to determine if a region will be filled.  Probably
-      // better to pass src_space->new_top() into decrement_destination_counts
-      // and test that instead.
-      //
-      // Clear the source_region field for each region in the space.
-      clear_source_region(space->bottom(), _space_info[id].new_top());
-
       // Reset the new_top value for the space.
       _space_info[id].set_new_top(space->bottom());
     } else if (live > 0) {
@@ -1854,7 +1894,6 @@
       dst_space_id = SpaceId(id);
       dst_space_end = space->end();
       new_top_addr = _space_info[id].new_top_addr();
-      HeapWord* const clear_end = _space_info[id].new_top();
       NOT_PRODUCT(summary_phase_msg(dst_space_id,
                                     space->bottom(), dst_space_end,
                                     SpaceId(id), next_src_addr, space->top());)
@@ -1865,13 +1904,6 @@
                                      new_top_addr);
       assert(done, "space must fit when compacted into itself");
       assert(*new_top_addr <= space->top(), "usage should not grow");
-
-      // XXX - this should go away.  See comments above.
-      //
-      // Clear the source_region field in regions at the end of the space that
-      // will not be filled.
-      HeapWord* const clear_beg = _summary_data.region_align_up(*new_top_addr);
-      clear_source_region(clear_beg, clear_end);
     }
   }
 
@@ -3051,19 +3083,34 @@
 }
 
 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
+                                                     SpaceId src_space_id,
                                                      size_t beg_region,
                                                      HeapWord* end_addr)
 {
   ParallelCompactData& sd = summary_data();
+
+#ifdef ASSERT
+  MutableSpace* const src_space = _space_info[src_space_id].space();
+  HeapWord* const beg_addr = sd.region_to_addr(beg_region);
+  assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
+         "src_space_id does not match beg_addr");
+  assert(src_space->contains(end_addr) || end_addr == src_space->end(),
+         "src_space_id does not match end_addr");
+#endif // #ifdef ASSERT
+
   RegionData* const beg = sd.region(beg_region);
-  HeapWord* const end_addr_aligned_up = sd.region_align_up(end_addr);
-  RegionData* const end = sd.addr_to_region_ptr(end_addr_aligned_up);
-  size_t cur_idx = beg_region;
-  for (RegionData* cur = beg; cur < end; ++cur, ++cur_idx) {
+  RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
+
+  // Regions up to new_top() are enqueued if they become available.
+  HeapWord* const new_top = _space_info[src_space_id].new_top();
+  RegionData* const enqueue_end =
+    sd.addr_to_region_ptr(sd.region_align_up(new_top));
+
+  for (RegionData* cur = beg; cur < end; ++cur) {
     assert(cur->data_size() > 0, "region must have live data");
     cur->decrement_destination_count();
-    if (cur_idx <= cur->source_region() && cur->available() && cur->claim()) {
-      cm->save_for_processing(cur_idx);
+    if (cur < enqueue_end && cur->available() && cur->claim()) {
+      cm->save_for_processing(sd.region(cur));
     }
   }
 }
@@ -3178,7 +3225,8 @@
     HeapWord* const old_src_addr = closure.source();
     closure.copy_partial_obj();
     if (closure.is_full()) {
-      decrement_destination_counts(cm, src_region_idx, closure.source());
+      decrement_destination_counts(cm, src_space_id, src_region_idx,
+                                   closure.source());
       region_ptr->set_deferred_obj_addr(NULL);
       region_ptr->set_completed();
       return;
@@ -3187,7 +3235,7 @@
     HeapWord* const end_addr = sd.region_align_down(closure.source());
     if (sd.region_align_down(old_src_addr) != end_addr) {
       // The partial object was copied from more than one source region.
-      decrement_destination_counts(cm, src_region_idx, end_addr);
+      decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
 
       // Move to the next source region, possibly switching spaces as well.  All
       // args except end_addr may be modified.
@@ -3227,19 +3275,21 @@
       region_ptr->set_deferred_obj_addr(closure.destination());
       status = closure.copy_until_full(); // copies from closure.source()
 
-      decrement_destination_counts(cm, src_region_idx, closure.source());
+      decrement_destination_counts(cm, src_space_id, src_region_idx,
+                                   closure.source());
       region_ptr->set_completed();
       return;
     }
 
     if (status == ParMarkBitMap::full) {
-      decrement_destination_counts(cm, src_region_idx, closure.source());
+      decrement_destination_counts(cm, src_space_id, src_region_idx,
+                                   closure.source());
       region_ptr->set_deferred_obj_addr(NULL);
       region_ptr->set_completed();
       return;
     }
 
-    decrement_destination_counts(cm, src_region_idx, end_addr);
+    decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
 
     // Move to the next source region, possibly switching spaces as well.  All
     // args except end_addr may be modified.
@@ -3318,7 +3368,7 @@
 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
 {
   if (source() != destination()) {
-    assert(source() > destination(), "must copy to the left");
+    DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
     Copy::aligned_conjoint_words(source(), destination(), words_remaining());
   }
   update_state(words_remaining());
@@ -3339,7 +3389,7 @@
   // This test is necessary; if omitted, the pointer updates to a partial object
   // that crosses the dense prefix boundary could be overwritten.
   if (source() != destination()) {
-    assert(source() > destination(), "must copy to the left");
+    DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
     Copy::aligned_conjoint_words(source(), destination(), words);
   }
   update_state(words);
@@ -3364,7 +3414,7 @@
   }
 
   if (destination() != source()) {
-    assert(destination() < source(), "must copy to the left");
+    DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
     Copy::aligned_conjoint_words(source(), destination(), words);
   }
 

--- a/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.hpp	Thu Dec 18 13:59:59 2008 -0800
+++ b/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.hpp	Fri Dec 19 12:15:34 2008 -0800
@@ -978,6 +978,10 @@
   // Include the new objects in the summary data.
   static void summarize_new_objects(SpaceId id, HeapWord* start);
 
+  // Add live objects to a survivor space since it's rare that both survivors
+  // are non-empty.
+  static void provoke_split_fill_survivor(SpaceId id);
+
   // Add live objects and/or choose the dense prefix to provoke splitting.
   static void provoke_split(bool & maximum_compaction);
 #endif
@@ -1154,8 +1158,10 @@
                                 HeapWord* end_addr);
 
   // Decrement the destination count for each non-empty source region in the
-  // range [beg_region, region(region_align_up(end_addr))).
+  // range [beg_region, region(region_align_up(end_addr))).  If the destination
+  // count for a region goes to 0 and it needs to be filled, enqueue it.
   static void decrement_destination_counts(ParCompactionManager* cm,
+                                           SpaceId src_space_id,
                                            size_t beg_region,
                                            HeapWord* end_addr);
 
@@ -1230,6 +1236,8 @@
 #endif  // #ifndef PRODUCT
 
 #ifdef  ASSERT
+  // Sanity check the new location of a word in the heap.
+  static inline void check_new_location(HeapWord* old_addr, HeapWord* new_addr);
   // Verify that all the regions have been emptied.
   static void verify_complete(SpaceId space_id);
 #endif  // #ifdef ASSERT
@@ -1397,6 +1405,15 @@
   }
 }
 
+#ifdef ASSERT
+inline void
+PSParallelCompact::check_new_location(HeapWord* old_addr, HeapWord* new_addr)
+{
+  assert(old_addr >= new_addr || space_id(old_addr) != space_id(new_addr),
+         "must move left or to a different space");
+}
+#endif // ASSERT
+
 class MoveAndUpdateClosure: public ParMarkBitMapClosure {
  public:
   inline MoveAndUpdateClosure(ParMarkBitMap* bitmap, ParCompactionManager* cm,

--- a/src/share/vm/gc_interface/collectedHeap.cpp	Thu Dec 18 13:59:59 2008 -0800
+++ b/src/share/vm/gc_interface/collectedHeap.cpp	Fri Dec 19 12:15:34 2008 -0800
@@ -178,8 +178,7 @@
 
   // Set the length first for concurrent GC.
   ((arrayOop)start)->set_length((int)len);
-  post_allocation_setup_common(Universe::fillerArrayKlassObj(), start,
-                               words);
+  post_allocation_setup_common(Universe::intArrayKlassObj(), start, words);
   DEBUG_ONLY(zap_filler_array(start, words);)
 }
 

--- a/src/share/vm/memory/universe.cpp	Thu Dec 18 13:59:59 2008 -0800
+++ b/src/share/vm/memory/universe.cpp	Fri Dec 19 12:15:34 2008 -0800
@@ -49,7 +49,6 @@
 klassOop Universe::_constantPoolCacheKlassObj         = NULL;
 klassOop Universe::_compiledICHolderKlassObj          = NULL;
 klassOop Universe::_systemObjArrayKlassObj            = NULL;
-klassOop Universe::_fillerArrayKlassObj               = NULL;
 oop Universe::_int_mirror                             = NULL;
 oop Universe::_float_mirror                           = NULL;
 oop Universe::_double_mirror                          = NULL;
@@ -127,7 +126,6 @@
   f(instanceKlassKlassObj());
   f(constantPoolKlassObj());
   f(systemObjArrayKlassObj());
-  f(fillerArrayKlassObj());
 }
 
 void Universe::oops_do(OopClosure* f, bool do_all) {
@@ -182,7 +180,6 @@
   f->do_oop((oop*)&_constantPoolCacheKlassObj);
   f->do_oop((oop*)&_compiledICHolderKlassObj);
   f->do_oop((oop*)&_systemObjArrayKlassObj);
-  f->do_oop((oop*)&_fillerArrayKlassObj);
   f->do_oop((oop*)&_the_empty_byte_array);
   f->do_oop((oop*)&_the_empty_short_array);
   f->do_oop((oop*)&_the_empty_int_array);
@@ -268,7 +265,6 @@
 
         _compiledICHolderKlassObj   = compiledICHolderKlass::create_klass(CHECK);
         _systemObjArrayKlassObj     = objArrayKlassKlass::cast(objArrayKlassKlassObj())->allocate_system_objArray_klass(CHECK);
-        _fillerArrayKlassObj        = typeArrayKlass::create_klass(T_INT, sizeof(jint), "<filler>", CHECK);
 
         _the_empty_byte_array       = oopFactory::new_permanent_byteArray(0, CHECK);
         _the_empty_short_array      = oopFactory::new_permanent_shortArray(0, CHECK);

--- a/src/share/vm/memory/universe.hpp	Thu Dec 18 13:59:59 2008 -0800
+++ b/src/share/vm/memory/universe.hpp	Fri Dec 19 12:15:34 2008 -0800
@@ -133,7 +133,6 @@
   static klassOop _constantPoolCacheKlassObj;
   static klassOop _compiledICHolderKlassObj;
   static klassOop _systemObjArrayKlassObj;
-  static klassOop _fillerArrayKlassObj;
 
   // Known objects in the VM
 
@@ -266,7 +265,6 @@
   static klassOop constantPoolCacheKlassObj()         { return _constantPoolCacheKlassObj; }
   static klassOop compiledICHolderKlassObj()          { return _compiledICHolderKlassObj;  }
   static klassOop systemObjArrayKlassObj()            { return _systemObjArrayKlassObj;    }
-  static klassOop fillerArrayKlassObj()               { return _fillerArrayKlassObj;       }
 
   // Known objects in tbe VM
   static oop int_mirror()                   { return check_mirror(_int_mirror);