6578152: fill_region_with_object has usability and safety issues

Reviewed-by: apetrusenko, ysr

hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -2954,7 +2954,7 @@ public:
       // The object has been either evacuated or is dead. Fill it with a
       // dummy object.
       MemRegion mr((HeapWord*)obj, obj->size());
-      SharedHeap::fill_region_with_object(mr);
+      CollectedHeap::fill_with_object(mr);
       _cm->clearRangeBothMaps(mr);
     }
   }
@@ -3225,7 +3225,7 @@ void G1CollectedHeap::par_allocate_remaining_space(HeapRegion* r) {
     // Otherwise, try to claim it.
     block = r->par_allocate(free_words);
   } while (block == NULL);
-  SharedHeap::fill_region_with_object(MemRegion(block, free_words));
+  fill_with_object(block, free_words);
 }
 
 #define use_local_bitmaps         1
@@ -3619,9 +3619,8 @@ public:
       guarantee(alloc_buffer(purpose)->contains(obj + word_sz - 1),
                 "should contain whole object");
       alloc_buffer(purpose)->undo_allocation(obj, word_sz);
-    }
-    else {
-      SharedHeap::fill_region_with_object(MemRegion(obj, word_sz));
+    } else {
+      CollectedHeap::fill_with_object(obj, word_sz);
       add_to_undo_waste(word_sz);
     }
   }

hotspot/src/share/vm/gc_implementation/g1/heapRegionSeq.cpp

@@ -102,7 +102,7 @@ HeapRegionSeq::alloc_obj_from_region_index(int ind, size_t word_size) {
       HeapWord* tmp = hr->allocate(sz);
       assert(tmp != NULL, "Humongous allocation failure");
       MemRegion mr = MemRegion(tmp, sz);
-      SharedHeap::fill_region_with_object(mr);
+      CollectedHeap::fill_with_object(mr);
       hr->declare_filled_region_to_BOT(mr);
       if (i == first) {
         first_hr->set_startsHumongous();

hotspot/src/share/vm/gc_implementation/parNew/parGCAllocBuffer.cpp

@@ -51,14 +51,14 @@ void ParGCAllocBuffer::retire(bool end_of_gc, bool retain) {
   if (_retained) {
     // If the buffer had been retained shorten the previous filler object.
     assert(_retained_filler.end() <= _top, "INVARIANT");
-    SharedHeap::fill_region_with_object(_retained_filler);
+    CollectedHeap::fill_with_object(_retained_filler);
     // Wasted space book-keeping, otherwise (normally) done in invalidate()
     _wasted += _retained_filler.word_size();
     _retained = false;
   }
   assert(!end_of_gc || !_retained, "At this point, end_of_gc ==> !_retained.");
   if (_top < _hard_end) {
-    SharedHeap::fill_region_with_object(MemRegion(_top, _hard_end));
+    CollectedHeap::fill_with_object(_top, _hard_end);
     if (!retain) {
       invalidate();
     } else {
@@ -155,7 +155,7 @@ ParGCAllocBufferWithBOT::ParGCAllocBufferWithBOT(size_t word_sz,
 // modifying the _next_threshold state in the BOT.
 void ParGCAllocBufferWithBOT::fill_region_with_block(MemRegion mr,
                                                      bool contig) {
-  SharedHeap::fill_region_with_object(mr);
+  CollectedHeap::fill_with_object(mr);
   if (contig) {
     _bt.alloc_block(mr.start(), mr.end());
   } else {
@@ -171,7 +171,7 @@ HeapWord* ParGCAllocBufferWithBOT::allocate_slow(size_t word_sz) {
            "or else _true_end should be equal to _hard_end");
     assert(_retained, "or else _true_end should be equal to _hard_end");
     assert(_retained_filler.end() <= _top, "INVARIANT");
-    SharedHeap::fill_region_with_object(_retained_filler);
+    CollectedHeap::fill_with_object(_retained_filler);
     if (_top < _hard_end) {
       fill_region_with_block(MemRegion(_top, _hard_end), true);
     }
@@ -316,11 +316,9 @@ void ParGCAllocBufferWithBOT::retire(bool end_of_gc, bool retain) {
         while (_top <= chunk_boundary) {
           assert(pointer_delta(_hard_end, chunk_boundary) >= AlignmentReserve,
                  "Consequence of last card handling above.");
-          MemRegion chunk_portion(chunk_boundary, _hard_end);
-          _bt.BlockOffsetArray::alloc_block(chunk_portion.start(),
-                                            chunk_portion.end());
-          SharedHeap::fill_region_with_object(chunk_portion);
-          _hard_end = chunk_portion.start();
+          _bt.BlockOffsetArray::alloc_block(chunk_boundary, _hard_end);
+          CollectedHeap::fill_with_object(chunk_boundary, _hard_end);
+          _hard_end = chunk_boundary;
           chunk_boundary -= ChunkSizeInWords;
         }
         _end = _hard_end - AlignmentReserve;

hotspot/src/share/vm/gc_implementation/parNew/parNewGeneration.cpp

@@ -201,7 +201,7 @@ void ParScanThreadState::undo_alloc_in_to_space(HeapWord* obj,
            "Should contain whole object.");
     to_space_alloc_buffer()->undo_allocation(obj, word_sz);
   } else {
-    SharedHeap::fill_region_with_object(MemRegion(obj, word_sz));
+    CollectedHeap::fill_with_object(obj, word_sz);
   }
 }
 

hotspot/src/share/vm/gc_implementation/parallelScavenge/psMarkSweep.cpp

@@ -389,7 +389,7 @@ bool PSMarkSweep::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
   // full GC.
   const size_t alignment = old_gen->virtual_space()->alignment();
   const size_t eden_used = eden_space->used_in_bytes();
-  const size_t promoted = (size_t)(size_policy->avg_promoted()->padded_average());
+  const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
   const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
   const size_t eden_capacity = eden_space->capacity_in_bytes();
 
@@ -416,16 +416,14 @@ bool PSMarkSweep::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
 
   // Fill the unused part of the old gen.
   MutableSpace* const old_space = old_gen->object_space();
-  MemRegion old_gen_unused(old_space->top(), old_space->end());
+  HeapWord* const unused_start = old_space->top();
+  size_t const unused_words = pointer_delta(old_space->end(), unused_start);
 
-  // If the unused part of the old gen cannot be filled, skip
-  // absorbing eden.
-  if (old_gen_unused.word_size() < SharedHeap::min_fill_size()) {
-    return false;
-  }
-
-  if (!old_gen_unused.is_empty()) {
-    SharedHeap::fill_region_with_object(old_gen_unused);
+  if (unused_words > 0) {
+    if (unused_words < CollectedHeap::min_fill_size()) {
+      return false;  // If the old gen cannot be filled, must give up.
+    }
+    CollectedHeap::fill_with_objects(unused_start, unused_words);
   }
 
   // Take the live data from eden and set both top and end in the old gen to
@@ -441,9 +439,8 @@ bool PSMarkSweep::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
 
   // Update the object start array for the filler object and the data from eden.
   ObjectStartArray* const start_array = old_gen->start_array();
-  HeapWord* const start = old_gen_unused.start();
-  for (HeapWord* addr = start; addr < new_top; addr += oop(addr)->size()) {
-    start_array->allocate_block(addr);
+  for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
+    start_array->allocate_block(p);
   }
 
   // Could update the promoted average here, but it is not typically updated at

hotspot/src/share/vm/gc_implementation/parallelScavenge/psMarkSweepDecorator.cpp

@@ -275,22 +275,9 @@ bool PSMarkSweepDecorator::insert_deadspace(size_t& allowed_deadspace_words,
                                             HeapWord* q, size_t deadlength) {
   if (allowed_deadspace_words >= deadlength) {
     allowed_deadspace_words -= deadlength;
-    oop(q)->set_mark(markOopDesc::prototype()->set_marked());
-    const size_t aligned_min_int_array_size =
-      align_object_size(typeArrayOopDesc::header_size(T_INT));
-    if (deadlength >= aligned_min_int_array_size) {
-      oop(q)->set_klass(Universe::intArrayKlassObj());
-      assert(((deadlength - aligned_min_int_array_size) * (HeapWordSize/sizeof(jint))) < (size_t)max_jint,
-                "deadspace too big for Arrayoop");
-      typeArrayOop(q)->set_length((int)((deadlength - aligned_min_int_array_size)
-                                            * (HeapWordSize/sizeof(jint))));
-    } else {
-      assert((int) deadlength == instanceOopDesc::header_size(),
-             "size for smallest fake dead object doesn't match");
-      oop(q)->set_klass(SystemDictionary::object_klass());
-    }
-    assert((int) deadlength == oop(q)->size(),
-           "make sure size for fake dead object match");
+    CollectedHeap::fill_with_object(q, deadlength);
+    oop(q)->set_mark(oop(q)->mark()->set_marked());
+    assert((int) deadlength == oop(q)->size(), "bad filler object size");
     // Recall that we required "q == compaction_top".
     return true;
   } else {

hotspot/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp

@@ -1308,8 +1308,7 @@ void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
     }
 #endif  // #ifdef _LP64
 
-    MemRegion region(obj_beg, obj_len);
-    SharedHeap::fill_region_with_object(region);
+    gc_heap()->fill_with_object(obj_beg, obj_len);
     _mark_bitmap.mark_obj(obj_beg, obj_len);
     _summary_data.add_obj(obj_beg, obj_len);
     assert(start_array(id) != NULL, "sanity");
@@ -1807,9 +1806,14 @@ bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_po
 
   // Fill the unused part of the old gen.
   MutableSpace* const old_space = old_gen->object_space();
-  MemRegion old_gen_unused(old_space->top(), old_space->end());
-  if (!old_gen_unused.is_empty()) {
-    SharedHeap::fill_region_with_object(old_gen_unused);
+  HeapWord* const unused_start = old_space->top();
+  size_t const unused_words = pointer_delta(old_space->end(), unused_start);
+
+  if (unused_words > 0) {
+    if (unused_words < CollectedHeap::min_fill_size()) {
+      return false;  // If the old gen cannot be filled, must give up.
+    }
+    CollectedHeap::fill_with_objects(unused_start, unused_words);
   }
 
   // Take the live data from eden and set both top and end in the old gen to
@@ -1825,9 +1829,8 @@ bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_po
 
   // Update the object start array for the filler object and the data from eden.
   ObjectStartArray* const start_array = old_gen->start_array();
-  HeapWord* const start = old_gen_unused.start();
-  for (HeapWord* addr = start; addr < new_top; addr += oop(addr)->size()) {
-    start_array->allocate_block(addr);
+  for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
+    start_array->allocate_block(p);
   }
 
   // Could update the promoted average here, but it is not typically updated at

hotspot/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.hpp

@@ -1324,31 +1324,28 @@ inline void UpdateOnlyClosure::do_addr(HeapWord* addr)
   oop(addr)->update_contents(compaction_manager());
 }
 
-class FillClosure: public ParMarkBitMapClosure {
- public:
+class FillClosure: public ParMarkBitMapClosure
+{
+public:
   FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) :
     ParMarkBitMapClosure(PSParallelCompact::mark_bitmap(), cm),
-    _space_id(space_id),
-    _start_array(PSParallelCompact::start_array(space_id)) {
-    assert(_space_id == PSParallelCompact::perm_space_id ||
-           _space_id == PSParallelCompact::old_space_id,
+    _start_array(PSParallelCompact::start_array(space_id))
+  {
+    assert(space_id == PSParallelCompact::perm_space_id ||
+           space_id == PSParallelCompact::old_space_id,
            "cannot use FillClosure in the young gen");
-    assert(bitmap() != NULL, "need a bitmap");
-    assert(_start_array != NULL, "need a start array");
-  }
-
-  void fill_region(HeapWord* addr, size_t size) {
-    MemRegion region(addr, size);
-    SharedHeap::fill_region_with_object(region);
-    _start_array->allocate_block(addr);
   }
 
   virtual IterationStatus do_addr(HeapWord* addr, size_t size) {
-    fill_region(addr, size);
+    CollectedHeap::fill_with_objects(addr, size);
+    HeapWord* const end = addr + size;
+    do {
+      _start_array->allocate_block(addr);
+      addr += oop(addr)->size();
+    } while (addr < end);
     return ParMarkBitMap::incomplete;
   }
 
 private:
-  const PSParallelCompact::SpaceId _space_id;
-  ObjectStartArray* const          _start_array;
+  ObjectStartArray* const _start_array;
 };

hotspot/src/share/vm/gc_implementation/parallelScavenge/psPromotionManager.cpp

@@ -499,26 +499,15 @@ oop PSPromotionManager::copy_to_survivor_space(oop o, bool depth_first) {
       // We lost, someone else "owns" this object
       guarantee(o->is_forwarded(), "Object must be forwarded if the cas failed.");
 
-      // Unallocate the space used. NOTE! We may have directly allocated
-      // the object. If so, we cannot deallocate it, so we have to test!
+      // Try to deallocate the space.  If it was directly allocated we cannot
+      // deallocate it, so we have to test.  If the deallocation fails,
+      // overwrite with a filler object.
       if (new_obj_is_tenured) {
         if (!_old_lab.unallocate_object(new_obj)) {
-          // The promotion lab failed to unallocate the object.
-          // We need to overwrite the object with a filler that
-          // contains no interior pointers.
-          MemRegion mr((HeapWord*)new_obj, new_obj_size);
-          // Clean this up and move to oopFactory (see bug 4718422)
-          SharedHeap::fill_region_with_object(mr);
-        }
-      } else {
-        if (!_young_lab.unallocate_object(new_obj)) {
-          // The promotion lab failed to unallocate the object.
-          // We need to overwrite the object with a filler that
-          // contains no interior pointers.
-          MemRegion mr((HeapWord*)new_obj, new_obj_size);
-          // Clean this up and move to oopFactory (see bug 4718422)
-          SharedHeap::fill_region_with_object(mr);
+          CollectedHeap::fill_with_object((HeapWord*) new_obj, new_obj_size);
         }
+      } else if (!_young_lab.unallocate_object(new_obj)) {
+        CollectedHeap::fill_with_object((HeapWord*) new_obj, new_obj_size);
       }
 
       // don't update this before the unallocation!

hotspot/src/share/vm/gc_implementation/shared/mutableNUMASpace.cpp

@@ -76,8 +76,8 @@ void MutableNUMASpace::ensure_parsability() {
     MutableSpace *s = ls->space();
     if (s->top() < top()) { // For all spaces preceeding the one containing top()
       if (s->free_in_words() > 0) {
-        SharedHeap::fill_region_with_object(MemRegion(s->top(), s->end()));
         size_t area_touched_words = pointer_delta(s->end(), s->top());
+        CollectedHeap::fill_with_object(s->top(), area_touched_words);
 #ifndef ASSERT
         if (!ZapUnusedHeapArea) {
           area_touched_words = MIN2((size_t)align_object_size(typeArrayOopDesc::header_size(T_INT)),
@@ -686,11 +686,11 @@ void MutableNUMASpace::set_top(HeapWord* value) {
       // a minimal object; assuming that's not the last chunk in which case we don't care.
       if (i < lgrp_spaces()->length() - 1) {
         size_t remainder = pointer_delta(s->end(), value);
-        const size_t minimal_object_size = oopDesc::header_size();
-        if (remainder < minimal_object_size && remainder > 0) {
-          // Add a filler object of a minimal size, it will cross the chunk boundary.
-          SharedHeap::fill_region_with_object(MemRegion(value, minimal_object_size));
-          value += minimal_object_size;
+        const size_t min_fill_size = CollectedHeap::min_fill_size();
+        if (remainder < min_fill_size && remainder > 0) {
+          // Add a minimum size filler object; it will cross the chunk boundary.
+          CollectedHeap::fill_with_object(value, min_fill_size);
+          value += min_fill_size;
           assert(!s->contains(value), "Should be in the next chunk");
           // Restart the loop from the same chunk, since the value has moved
           // to the next one.

hotspot/src/share/vm/gc_interface/collectedHeap.cpp

@@ -30,12 +30,21 @@
 int CollectedHeap::_fire_out_of_memory_count = 0;
 #endif
 
+size_t CollectedHeap::_filler_array_max_size = 0;
+
 // Memory state functions.
 
-CollectedHeap::CollectedHeap() :
-  _reserved(), _barrier_set(NULL), _is_gc_active(false),
-  _total_collections(0), _total_full_collections(0),
-  _gc_cause(GCCause::_no_gc), _gc_lastcause(GCCause::_no_gc) {
+CollectedHeap::CollectedHeap()
+{
+  const size_t max_len = size_t(arrayOopDesc::max_array_length(T_INT));
+  const size_t elements_per_word = HeapWordSize / sizeof(jint);
+  _filler_array_max_size = align_object_size(filler_array_hdr_size() +
+                                             max_len * elements_per_word);
+
+  _barrier_set = NULL;
+  _is_gc_active = false;
+  _total_collections = _total_full_collections = 0;
+  _gc_cause = _gc_lastcause = GCCause::_no_gc;
   NOT_PRODUCT(_promotion_failure_alot_count = 0;)
   NOT_PRODUCT(_promotion_failure_alot_gc_number = 0;)
 
@@ -128,6 +137,95 @@ HeapWord* CollectedHeap::allocate_from_tlab_slow(Thread* thread, size_t size) {
   return obj;
 }
 
+size_t CollectedHeap::filler_array_hdr_size() {
+  return size_t(arrayOopDesc::header_size(T_INT));
+}
+
+size_t CollectedHeap::filler_array_min_size() {
+  return align_object_size(filler_array_hdr_size());
+}
+
+size_t CollectedHeap::filler_array_max_size() {
+  return _filler_array_max_size;
+}
+
+#ifdef ASSERT
+void CollectedHeap::fill_args_check(HeapWord* start, size_t words)
+{
+  assert(words >= min_fill_size(), "too small to fill");
+  assert(words % MinObjAlignment == 0, "unaligned size");
+  assert(Universe::heap()->is_in_reserved(start), "not in heap");
+  assert(Universe::heap()->is_in_reserved(start + words - 1), "not in heap");
+}
+
+void CollectedHeap::zap_filler_array(HeapWord* start, size_t words)
+{
+  if (ZapFillerObjects) {
+    Copy::fill_to_words(start + filler_array_hdr_size(),
+                        words - filler_array_hdr_size(), 0XDEAFBABE);
+  }
+}
+#endif // ASSERT
+
+void
+CollectedHeap::fill_with_array(HeapWord* start, size_t words)
+{
+  assert(words >= filler_array_min_size(), "too small for an array");
+  assert(words <= filler_array_max_size(), "too big for a single object");
+
+  const size_t payload_size = words - filler_array_hdr_size();
+  const size_t len = payload_size * HeapWordSize / sizeof(jint);
+
+  // Set the length first for concurrent GC.
+  ((arrayOop)start)->set_length((int)len);
+  post_allocation_setup_common(Universe::fillerArrayKlassObj(), start,
+                               words);
+  DEBUG_ONLY(zap_filler_array(start, words);)
+}
+
+void
+CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words)
+{
+  assert(words <= filler_array_max_size(), "too big for a single object");
+
+  if (words >= filler_array_min_size()) {
+    fill_with_array(start, words);
+  } else if (words > 0) {
+    assert(words == min_fill_size(), "unaligned size");
+    post_allocation_setup_common(SystemDictionary::object_klass(), start,
+                                 words);
+  }
+}
+
+void CollectedHeap::fill_with_object(HeapWord* start, size_t words)
+{
+  DEBUG_ONLY(fill_args_check(start, words);)
+  HandleMark hm;  // Free handles before leaving.
+  fill_with_object_impl(start, words);
+}
+
+void CollectedHeap::fill_with_objects(HeapWord* start, size_t words)
+{
+  DEBUG_ONLY(fill_args_check(start, words);)
+  HandleMark hm;  // Free handles before leaving.
+
+#ifdef LP64
+  // A single array can fill ~8G, so multiple objects are needed only in 64-bit.
+  // First fill with arrays, ensuring that any remaining space is big enough to
+  // fill.  The remainder is filled with a single object.
+  const size_t min = min_fill_size();
+  const size_t max = filler_array_max_size();
+  while (words > max) {
+    const size_t cur = words - max >= min ? max : max - min;
+    fill_with_array(start, cur);
+    start += cur;
+    words -= cur;
+  }
+#endif
+
+  fill_with_object_impl(start, words);
+}
+
 oop CollectedHeap::new_store_barrier(oop new_obj) {
   // %%% This needs refactoring.  (It was imported from the server compiler.)
   guarantee(can_elide_tlab_store_barriers(), "store barrier elision not supported");

hotspot/src/share/vm/gc_interface/collectedHeap.hpp

@@ -47,6 +47,9 @@ class CollectedHeap : public CHeapObj {
   static int       _fire_out_of_memory_count;
 #endif
 
+  // Used for filler objects (static, but initialized in ctor).
+  static size_t _filler_array_max_size;
+
  protected:
   MemRegion _reserved;
   BarrierSet* _barrier_set;
@@ -119,6 +122,21 @@ class CollectedHeap : public CHeapObj {
   // Clears an allocated object.
   inline static void init_obj(HeapWord* obj, size_t size);
 
+  // Filler object utilities.
+  static inline size_t filler_array_hdr_size();
+  static inline size_t filler_array_min_size();
+  static inline size_t filler_array_max_size();
+
+  DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
+  DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words);)
+
+  // Fill with a single array; caller must ensure filler_array_min_size() <=
+  // words <= filler_array_max_size().
+  static inline void fill_with_array(HeapWord* start, size_t words);
+
+  // Fill with a single object (either an int array or a java.lang.Object).
+  static inline void fill_with_object_impl(HeapWord* start, size_t words);
+
   // Verification functions
   virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
     PRODUCT_RETURN;
@@ -294,6 +312,27 @@ class CollectedHeap : public CHeapObj {
   // The boundary between a "large" and "small" array of primitives, in words.
   virtual size_t large_typearray_limit() = 0;
 
+  // Utilities for turning raw memory into filler objects.
+  //
+  // min_fill_size() is the smallest region that can be filled.
+  // fill_with_objects() can fill arbitrary-sized regions of the heap using
+  // multiple objects.  fill_with_object() is for regions known to be smaller
+  // than the largest array of integers; it uses a single object to fill the
+  // region and has slightly less overhead.
+  static size_t min_fill_size() {
+    return size_t(align_object_size(oopDesc::header_size()));
+  }
+
+  static void fill_with_objects(HeapWord* start, size_t words);
+
+  static void fill_with_object(HeapWord* start, size_t words);
+  static void fill_with_object(MemRegion region) {
+    fill_with_object(region.start(), region.word_size());
+  }
+  static void fill_with_object(HeapWord* start, HeapWord* end) {
+    fill_with_object(start, pointer_delta(end, start));
+  }
+
   // Some heaps may offer a contiguous region for shared non-blocking
   // allocation, via inlined code (by exporting the address of the top and
   // end fields defining the extent of the contiguous allocation region.)

hotspot/src/share/vm/gc_interface/collectedHeap.inline.hpp

@@ -34,7 +34,6 @@ void CollectedHeap::post_allocation_setup_common(KlassHandle klass,
 void CollectedHeap::post_allocation_setup_no_klass_install(KlassHandle klass,
                                                            HeapWord* objPtr,
                                                            size_t size) {
-
   oop obj = (oop)objPtr;
 
   assert(obj != NULL, "NULL object pointer");
@@ -44,9 +43,6 @@ void CollectedHeap::post_allocation_setup_no_klass_install(KlassHandle klass,
     // May be bootstrapping
     obj->set_mark(markOopDesc::prototype());
   }
-
-  // support low memory notifications (no-op if not enabled)
-  LowMemoryDetector::detect_low_memory_for_collected_pools();
 }
 
 void CollectedHeap::post_allocation_install_obj_klass(KlassHandle klass,
@@ -65,6 +61,9 @@ void CollectedHeap::post_allocation_install_obj_klass(KlassHandle klass,
 
 // Support for jvmti and dtrace
 inline void post_allocation_notify(KlassHandle klass, oop obj) {
+  // support low memory notifications (no-op if not enabled)
+  LowMemoryDetector::detect_low_memory_for_collected_pools();
+
   // support for JVMTI VMObjectAlloc event (no-op if not enabled)
   JvmtiExport::vm_object_alloc_event_collector(obj);
 

hotspot/src/share/vm/includeDB_gc

@@ -28,21 +28,22 @@ collectedHeap.cpp                       collectedHeap.hpp
 collectedHeap.cpp                       collectedHeap.inline.hpp
 collectedHeap.cpp                       init.hpp
 collectedHeap.cpp                       oop.inline.hpp
+collectedHeap.cpp                       systemDictionary.hpp
 collectedHeap.cpp                       thread_<os_family>.inline.hpp
 
 collectedHeap.hpp                       allocation.hpp
 collectedHeap.hpp                       barrierSet.hpp
 collectedHeap.hpp                       gcCause.hpp
 collectedHeap.hpp                       handles.hpp
-collectedHeap.hpp			perfData.hpp
+collectedHeap.hpp                       perfData.hpp
 collectedHeap.hpp                       safepoint.hpp
 
 collectedHeap.inline.hpp                arrayOop.hpp
 collectedHeap.inline.hpp                collectedHeap.hpp
 collectedHeap.inline.hpp                copy.hpp
 collectedHeap.inline.hpp                jvmtiExport.hpp
-collectedHeap.inline.hpp		            lowMemoryDetector.hpp
-collectedHeap.inline.hpp		            sharedRuntime.hpp
+collectedHeap.inline.hpp                lowMemoryDetector.hpp
+collectedHeap.inline.hpp                sharedRuntime.hpp
 collectedHeap.inline.hpp                thread.hpp
 collectedHeap.inline.hpp                threadLocalAllocBuffer.inline.hpp
 collectedHeap.inline.hpp                universe.hpp

hotspot/src/share/vm/memory/sharedHeap.cpp

@@ -248,46 +248,6 @@ void SharedHeap::ref_processing_init() {
   perm_gen()->ref_processor_init();
 }
 
-void SharedHeap::fill_region_with_object(MemRegion mr) {
-  // Disable the posting of JVMTI VMObjectAlloc events as we
-  // don't want the filling of tlabs with filler arrays to be
-  // reported to the profiler.
-  NoJvmtiVMObjectAllocMark njm;
-
-  // Disable low memory detector because there is no real allocation.
-  LowMemoryDetectorDisabler lmd_dis;
-
-  // It turns out that post_allocation_setup_array takes a handle, so the
-  // call below contains an implicit conversion.  Best to free that handle
-  // as soon as possible.
-  HandleMark hm;
-
-  size_t word_size = mr.word_size();
-  size_t aligned_array_header_size =
-    align_object_size(typeArrayOopDesc::header_size(T_INT));
-
-  if (word_size >= aligned_array_header_size) {
-    const size_t array_length =
-      pointer_delta(mr.end(), mr.start()) -
-      typeArrayOopDesc::header_size(T_INT);
-    const size_t array_length_words =
-      array_length * (HeapWordSize/sizeof(jint));
-    post_allocation_setup_array(Universe::intArrayKlassObj(),
-                                mr.start(),
-                                mr.word_size(),
-                                (int)array_length_words);
-#ifdef ASSERT
-    HeapWord* elt_words = (mr.start() + typeArrayOopDesc::header_size(T_INT));
-    Copy::fill_to_words(elt_words, array_length, 0xDEAFBABE);
-#endif
-  } else {
-    assert(word_size == (size_t)oopDesc::header_size(), "Unaligned?");
-    post_allocation_setup_obj(SystemDictionary::object_klass(),
-                              mr.start(),
-                              mr.word_size());
-  }
-}
-
 // Some utilities.
 void SharedHeap::print_size_transition(outputStream* out,
                                        size_t bytes_before,

hotspot/src/share/vm/memory/sharedHeap.hpp

@@ -108,14 +108,6 @@ public:
 
   void set_perm(PermGen* perm_gen) { _perm_gen = perm_gen; }
 
-  // A helper function that fills a region of the heap with
-  // with a single object.
-  static void fill_region_with_object(MemRegion mr);
-
-  // Minimum garbage fill object size
-  static size_t min_fill_size()          { return (size_t)align_object_size(oopDesc::header_size()); }
-  static size_t min_fill_size_in_bytes() { return min_fill_size() * HeapWordSize; }
-
   // This function returns the "GenRemSet" object that allows us to scan
   // generations; at least the perm gen, possibly more in a fully
   // generational heap.

hotspot/src/share/vm/memory/space.cpp

@@ -409,19 +409,9 @@ bool CompactibleSpace::insert_deadspace(size_t& allowed_deadspace_words,
                                         HeapWord* q, size_t deadlength) {
   if (allowed_deadspace_words >= deadlength) {
     allowed_deadspace_words -= deadlength;
-    oop(q)->set_mark(markOopDesc::prototype()->set_marked());
-    const size_t min_int_array_size = typeArrayOopDesc::header_size(T_INT);
-    if (deadlength >= min_int_array_size) {
-      oop(q)->set_klass(Universe::intArrayKlassObj());
-      typeArrayOop(q)->set_length((int)((deadlength - min_int_array_size)
-                                            * (HeapWordSize/sizeof(jint))));
-    } else {
-      assert((int) deadlength == instanceOopDesc::header_size(),
-             "size for smallest fake dead object doesn't match");
-      oop(q)->set_klass(SystemDictionary::object_klass());
-    }
-    assert((int) deadlength == oop(q)->size(),
-           "make sure size for fake dead object match");
+    CollectedHeap::fill_with_object(q, deadlength);
+    oop(q)->set_mark(oop(q)->mark()->set_marked());
+    assert((int) deadlength == oop(q)->size(), "bad filler object size");
     // Recall that we required "q == compaction_top".
     return true;
   } else {

hotspot/src/share/vm/memory/tenuredGeneration.cpp

@@ -387,7 +387,7 @@ void TenuredGeneration::par_promote_alloc_undo(int thread_num,
               "should contain whole object");
     buf->undo_allocation(obj, word_sz);
   } else {
-    SharedHeap::fill_region_with_object(MemRegion(obj, word_sz));
+    CollectedHeap::fill_with_object(obj, word_sz);
   }
 }
 

hotspot/src/share/vm/memory/threadLocalAllocBuffer.cpp

@@ -100,8 +100,7 @@ void ThreadLocalAllocBuffer::accumulate_statistics() {
 void ThreadLocalAllocBuffer::make_parsable(bool retire) {
   if (end() != NULL) {
     invariants();
-    MemRegion mr(top(), hard_end());
-    SharedHeap::fill_region_with_object(mr);
+    CollectedHeap::fill_with_object(top(), hard_end());
 
     if (retire || ZeroTLAB) {  // "Reset" the TLAB
       set_start(NULL);

hotspot/src/share/vm/memory/universe.cpp

@@ -49,16 +49,17 @@ klassOop Universe::_constantPoolKlassObj              = NULL;
 klassOop Universe::_constantPoolCacheKlassObj         = NULL;
 klassOop Universe::_compiledICHolderKlassObj          = NULL;
 klassOop Universe::_systemObjArrayKlassObj            = NULL;
-oop Universe::_int_mirror                             =  NULL;
-oop Universe::_float_mirror                           =  NULL;
-oop Universe::_double_mirror                          =  NULL;
-oop Universe::_byte_mirror                            =  NULL;
-oop Universe::_bool_mirror                            =  NULL;
-oop Universe::_char_mirror                            =  NULL;
-oop Universe::_long_mirror                            =  NULL;
-oop Universe::_short_mirror                           =  NULL;
-oop Universe::_void_mirror                            =  NULL;
-oop Universe::_mirrors[T_VOID+1]                      =  { NULL /*, NULL...*/ };
+klassOop Universe::_fillerArrayKlassObj               = NULL;
+oop Universe::_int_mirror                             = NULL;
+oop Universe::_float_mirror                           = NULL;
+oop Universe::_double_mirror                          = NULL;
+oop Universe::_byte_mirror                            = NULL;
+oop Universe::_bool_mirror                            = NULL;
+oop Universe::_char_mirror                            = NULL;
+oop Universe::_long_mirror                            = NULL;
+oop Universe::_short_mirror                           = NULL;
+oop Universe::_void_mirror                            = NULL;
+oop Universe::_mirrors[T_VOID+1]                      = { NULL /*, NULL...*/ };
 oop Universe::_main_thread_group                      = NULL;
 oop Universe::_system_thread_group                    = NULL;
 typeArrayOop Universe::_the_empty_byte_array          = NULL;
@@ -126,6 +127,7 @@ void Universe::system_classes_do(void f(klassOop)) {
   f(instanceKlassKlassObj());
   f(constantPoolKlassObj());
   f(systemObjArrayKlassObj());
+  f(fillerArrayKlassObj());
 }
 
 void Universe::oops_do(OopClosure* f, bool do_all) {
@@ -180,6 +182,7 @@ void Universe::oops_do(OopClosure* f, bool do_all) {
   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);
@@ -257,16 +260,17 @@ void Universe::genesis(TRAPS) {
         _typeArrayKlassObjs[T_INT]     = _intArrayKlassObj;
         _typeArrayKlassObjs[T_LONG]    = _longArrayKlassObj;
 
-        _methodKlassObj         = methodKlass::create_klass(CHECK);
-        _constMethodKlassObj    = constMethodKlass::create_klass(CHECK);
-        _methodDataKlassObj     = methodDataKlass::create_klass(CHECK);
+        _methodKlassObj             = methodKlass::create_klass(CHECK);
+        _constMethodKlassObj        = constMethodKlass::create_klass(CHECK);
+        _methodDataKlassObj         = methodDataKlass::create_klass(CHECK);
         _constantPoolKlassObj       = constantPoolKlass::create_klass(CHECK);
         _constantPoolCacheKlassObj  = constantPoolCacheKlass::create_klass(CHECK);
 
         _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_byte_array       = oopFactory::new_permanent_byteArray(0, CHECK);
         _the_empty_short_array      = oopFactory::new_permanent_shortArray(0, CHECK);
         _the_empty_int_array        = oopFactory::new_permanent_intArray(0, CHECK);
         _the_empty_system_obj_array = oopFactory::new_system_objArray(0, CHECK);
@@ -274,7 +278,6 @@ void Universe::genesis(TRAPS) {
         _the_array_interfaces_array = oopFactory::new_system_objArray(2, CHECK);
         _vm_exception               = oopFactory::new_symbol("vm exception holder", CHECK);
       } else {
-
         FileMapInfo *mapinfo = FileMapInfo::current_info();
         char* buffer = mapinfo->region_base(CompactingPermGenGen::md);
         void** vtbl_list = (void**)buffer;

hotspot/src/share/vm/memory/universe.hpp

@@ -92,6 +92,7 @@ class LatestMethodOopCache : public CommonMethodOopCache {
 
 
 class Universe: AllStatic {
+  // Ugh.  Universe is much too friendly.
   friend class MarkSweep;
   friend class oopDesc;
   friend class ClassLoader;
@@ -132,6 +133,7 @@ class Universe: AllStatic {
   static klassOop _constantPoolCacheKlassObj;
   static klassOop _compiledICHolderKlassObj;
   static klassOop _systemObjArrayKlassObj;
+  static klassOop _fillerArrayKlassObj;
 
   // Known objects in the VM
 
@@ -264,6 +266,7 @@ class Universe: AllStatic {
   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);

hotspot/src/share/vm/oops/arrayOop.hpp

@@ -96,19 +96,20 @@ class arrayOopDesc : public oopDesc {
       : typesize_in_bytes/HeapWordSize);
   }
 
-  // This method returns the  maximum length that can passed into
-  // typeArrayOop::object_size(scale, length, header_size) without causing an
-  // overflow. We substract an extra 2*wordSize to guard against double word
-  // alignments.  It gets the scale from the type2aelembytes array.
+  // Return the maximum length of an array of BasicType.  The length can passed
+  // to typeArrayOop::object_size(scale, length, header_size) without causing an
+  // overflow.
   static int32_t max_array_length(BasicType type) {
     assert(type >= 0 && type < T_CONFLICT, "wrong type");
     assert(type2aelembytes(type) != 0, "wrong type");
-    // We use max_jint, since object_size is internally represented by an 'int'
-    // This gives us an upper bound of max_jint words for the size of the oop.
-    int32_t max_words = (max_jint - header_size(type) - 2);
-    int elembytes = type2aelembytes(type);
-    jlong len = ((jlong)max_words * HeapWordSize) / elembytes;
-    return (len > max_jint) ? max_jint : (int32_t)len;
-  }
+    const int bytes_per_element = type2aelembytes(type);
+    if (bytes_per_element < HeapWordSize) {
+      return max_jint;
+    }
 
+    const int32_t max_words = align_size_down(max_jint, MinObjAlignment);
+    const int32_t max_element_words = max_words - header_size(type);
+    const int32_t words_per_element = bytes_per_element >> LogHeapWordSize;
+    return max_element_words / words_per_element;
+  }
 };

hotspot/src/share/vm/oops/typeArrayKlass.cpp

@@ -36,13 +36,14 @@ bool typeArrayKlass::compute_is_subtype_of(klassOop k) {
   return element_type() == tak->element_type();
 }
 
-klassOop typeArrayKlass::create_klass(BasicType type, int scale, TRAPS) {
+klassOop typeArrayKlass::create_klass(BasicType type, int scale,
+                                      const char* name_str, TRAPS) {
   typeArrayKlass o;
 
   symbolHandle sym(symbolOop(NULL));
   // bootstrapping: don't create sym if symbolKlass not created yet
-  if (Universe::symbolKlassObj() != NULL) {
-    sym = oopFactory::new_symbol_handle(external_name(type), CHECK_NULL);
+  if (Universe::symbolKlassObj() != NULL && name_str != NULL) {
+    sym = oopFactory::new_symbol_handle(name_str, CHECK_NULL);
   }
   KlassHandle klassklass (THREAD, Universe::typeArrayKlassKlassObj());
 

hotspot/src/share/vm/oops/typeArrayKlass.hpp

@@ -39,7 +39,11 @@ class typeArrayKlass : public arrayKlass {
 
   // klass allocation
   DEFINE_ALLOCATE_PERMANENT(typeArrayKlass);
-  static klassOop create_klass(BasicType type, int scale, TRAPS);
+  static klassOop create_klass(BasicType type, int scale, const char* name_str,
+                               TRAPS);
+  static inline klassOop create_klass(BasicType type, int scale, TRAPS) {
+    return create_klass(type, scale, external_name(type), CHECK_NULL);
+  }
 
   int oop_size(oop obj) const;
   int klass_oop_size() const  { return object_size(); }

hotspot/src/share/vm/runtime/globals.hpp

@@ -625,6 +625,9 @@ class CommandLineFlags {
   develop(bool, CheckZapUnusedHeapArea, false,                              \
           "Check zapping of unused heap space")                             \
                                                                             \
+  develop(bool, ZapFillerObjects, trueInDebug,                              \
+          "Zap filler objects with 0xDEAFBABE")                             \
+                                                                            \
   develop(bool, PrintVMMessages, true,                                      \
           "Print vm messages on console")                                   \
                                                                             \