8255232: G1: Make G1BiasedMappedArray freeable

Reviewed-by: ayang, kbarrett

src/hotspot/share/gc/g1/g1BiasedArray.cpp

@@ -26,11 +26,23 @@
 #include "gc/g1/g1BiasedArray.hpp"
 #include "memory/padded.inline.hpp"
 
+G1BiasedMappedArrayBase::G1BiasedMappedArrayBase() :
+  _alloc_base(NULL),
+  _base(NULL),
+  _length(0),
+  _biased_base(NULL),
+  _bias(0),
+  _shift_by(0) { }
+
+G1BiasedMappedArrayBase::~G1BiasedMappedArrayBase() {
+  FreeHeap(_alloc_base);
+}
+
 // Allocate a new array, generic version.
 address G1BiasedMappedArrayBase::create_new_base_array(size_t length, size_t elem_size) {
   assert(length > 0, "just checking");
   assert(elem_size > 0, "just checking");
-  return PaddedPrimitiveArray<u_char, mtGC>::create_unfreeable(length * elem_size);
+  return PaddedPrimitiveArray<u_char, mtGC>::create(length * elem_size, &_alloc_base);
 }
 
 #ifndef PRODUCT

src/hotspot/share/gc/g1/g1BiasedArray.hpp

@@ -25,17 +25,22 @@
 #ifndef SHARE_GC_G1_G1BIASEDARRAY_HPP
 #define SHARE_GC_G1_G1BIASEDARRAY_HPP
 
+#include "memory/allocation.hpp"
 #include "memory/memRegion.hpp"
 #include "utilities/debug.hpp"
 #include "utilities/powerOfTwo.hpp"
 
 // Implements the common base functionality for arrays that contain provisions
 // for accessing its elements using a biased index.
 // The element type is defined by the instantiating the template.
-class G1BiasedMappedArrayBase {
+class G1BiasedMappedArrayBase : public CHeapObj<mtGC> {
   friend class VMStructs;
+
+  void* _alloc_base;      // the address the unpadded array has been allocated to
+
 public:
   typedef size_t idx_t;
+
 protected:
   address _base;          // the real base address
   size_t _length;         // the length of the array
@@ -44,12 +49,10 @@ class G1BiasedMappedArrayBase {
   uint _shift_by;         // the amount of bits to shift right when mapping to an index of the array.
 
 protected:
-
-  G1BiasedMappedArrayBase() : _base(NULL), _length(0), _biased_base(NULL),
-    _bias(0), _shift_by(0) { }
+  G1BiasedMappedArrayBase();
 
   // Allocate a new array, generic version.
-  static address create_new_base_array(size_t length, size_t elem_size);
+  address create_new_base_array(size_t length, size_t elem_size);
 
   // Initialize the members of this class. The biased start address of this array
   // is the bias (in elements) multiplied by the element size.
@@ -90,8 +93,10 @@ class G1BiasedMappedArrayBase {
   void verify_biased_index_inclusive_end(idx_t biased_index) const PRODUCT_RETURN;
 
 public:
-   // Return the length of the array in elements.
-   size_t length() const { return _length; }
+  virtual ~G1BiasedMappedArrayBase();
+
+  // Return the length of the array in elements.
+  size_t length() const { return _length; }
 };
 
 // Array that provides biased access and mapping from (valid) addresses in the

src/hotspot/share/memory/padded.hpp

@@ -116,6 +116,7 @@ template <class T, MEMFLAGS flags, size_t alignment = DEFAULT_CACHE_LINE_SIZE>
 class PaddedPrimitiveArray {
  public:
   static T* create_unfreeable(size_t length);
+  static T* create(size_t length, void** alloc_base);
 };
 
 #endif // SHARE_MEMORY_PADDED_HPP

src/hotspot/share/memory/padded.inline.hpp

@@ -82,11 +82,18 @@ T** Padded2DArray<T, flags, alignment>::create_unfreeable(uint rows, uint column
 
 template <class T, MEMFLAGS flags, size_t alignment>
 T* PaddedPrimitiveArray<T, flags, alignment>::create_unfreeable(size_t length) {
+  void* temp;
+  return create(length, &temp);
+}
+
+template <class T, MEMFLAGS flags, size_t alignment>
+T* PaddedPrimitiveArray<T, flags, alignment>::create(size_t length, void** alloc_base) {
   // Allocate a chunk of memory large enough to allow for some alignment.
   void* chunk = AllocateHeap(length * sizeof(T) + alignment, flags);
 
   memset(chunk, 0, length * sizeof(T) + alignment);
 
+  *alloc_base = chunk;
   return (T*)align_up(chunk, alignment);
 }