1 /*
   2  * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_MEMORY_HEAP_HPP
  26 #define SHARE_VM_MEMORY_HEAP_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "runtime/virtualspace.hpp"
  30 
  31 // Blocks
  32 
  33 class HeapBlock VALUE_OBJ_CLASS_SPEC {
  34   friend class VMStructs;
  35 
  36  public:
  37   struct Header {
  38     size_t  _length;                             // the length in segments
  39     bool    _used;                               // Used bit
  40   };
  41 
  42  protected:
  43   union {
  44     Header _header;
  45     int64_t _padding[ (sizeof(Header) + sizeof(int64_t)-1) / sizeof(int64_t) ];
  46                         // pad to 0 mod 8
  47   };
  48 
  49  public:
  50   // Initialization
  51   void initialize(size_t length)                 { _header._length = length; set_used(); }
  52 
  53   // Accessors
  54   void* allocated_space() const                  { return (void*)(this + 1); }
  55   size_t length() const                          { return _header._length; }
  56 
  57   // Used/free
  58   void set_used()                                { _header._used = true; }
  59   void set_free()                                { _header._used = false; }
  60   bool free()                                    { return !_header._used; }
  61 };
  62 
  63 class FreeBlock: public HeapBlock {
  64   friend class VMStructs;
  65  protected:
  66   FreeBlock* _link;
  67 
  68  public:
  69   // Initialization
  70   void initialize(size_t length)             { HeapBlock::initialize(length); _link= NULL; }
  71 
  72   // Merging
  73   void set_length(size_t l)                  { _header._length = l; }
  74 
  75   // Accessors
  76   FreeBlock* link() const                    { return _link; }
  77   void set_link(FreeBlock* link)             { _link = link; }
  78 };
  79 
  80 class CodeHeap : public CHeapObj<mtCode> {
  81   friend class VMStructs;
  82  private:
  83   VirtualSpace _memory;                          // the memory holding the blocks
  84   VirtualSpace _segmap;                          // the memory holding the segment map
  85 
  86   size_t       _number_of_committed_segments;
  87   size_t       _number_of_reserved_segments;
  88   size_t       _segment_size;
  89   int          _log2_segment_size;
  90 
  91   size_t       _next_segment;
  92 
  93   FreeBlock*   _freelist;
  94   size_t       _freelist_segments;               // No. of segments in freelist
  95 
  96   // Helper functions
  97   size_t   size_to_segments(size_t size) const { return (size + _segment_size - 1) >> _log2_segment_size; }
  98   size_t   segments_to_size(size_t number_of_segments) const { return number_of_segments << _log2_segment_size; }
  99 
 100   size_t   segment_for(void* p) const            { return ((char*)p - _memory.low()) >> _log2_segment_size; }
 101   HeapBlock* block_at(size_t i) const            { return (HeapBlock*)(_memory.low() + (i << _log2_segment_size)); }
 102 
 103   void  mark_segmap_as_free(size_t beg, size_t end);
 104   void  mark_segmap_as_used(size_t beg, size_t end);
 105 
 106   // Freelist management helpers
 107   FreeBlock* following_block(FreeBlock *b);
 108   void insert_after(FreeBlock* a, FreeBlock* b);
 109   void merge_right (FreeBlock* a);
 110 
 111   // Toplevel freelist management
 112   void add_to_freelist(HeapBlock *b);
 113   FreeBlock* search_freelist(size_t length, bool is_critical);
 114 
 115   // Iteration helpers
 116   void*      next_free(HeapBlock* b) const;
 117   HeapBlock* first_block() const;
 118   HeapBlock* next_block(HeapBlock* b) const;
 119   HeapBlock* block_start(void* p) const;
 120 
 121   // to perform additional actions on creation of executable code
 122   void on_code_mapping(char* base, size_t size);
 123 
 124  public:
 125   CodeHeap();
 126 
 127   // Heap extents
 128   bool  reserve(size_t reserved_size, size_t committed_size, size_t segment_size);
 129   void  release();                               // releases all allocated memory
 130   bool  expand_by(size_t size);                  // expands commited memory by size
 131   void  shrink_by(size_t size);                  // shrinks commited memory by size
 132   void  clear();                                 // clears all heap contents
 133 
 134   // Memory allocation
 135   void* allocate  (size_t size, bool is_critical);  // allocates a block of size or returns NULL
 136   void  deallocate(void* p);                     // deallocates a block
 137 
 138   // Attributes
 139   char* low_boundary() const                     { return _memory.low_boundary (); }
 140   char* high() const                             { return _memory.high(); }
 141   char* high_boundary() const                    { return _memory.high_boundary(); }
 142 
 143   bool  contains(const void* p) const            { return low_boundary() <= p && p < high(); }
 144   void* find_start(void* p) const;              // returns the block containing p or NULL
 145   size_t alignment_unit() const;                // alignment of any block
 146   size_t alignment_offset() const;              // offset of first byte of any block, within the enclosing alignment unit
 147   static size_t header_size();                  // returns the header size for each heap block
 148 
 149   // Iteration
 150 
 151   // returns the first block or NULL
 152   void* first() const       { return next_free(first_block()); }
 153   // returns the next block given a block p or NULL
 154   void* next(void* p) const { return next_free(next_block(block_start(p))); }
 155 
 156   // Statistics
 157   size_t capacity() const;
 158   size_t max_capacity() const;
 159   size_t allocated_capacity() const;
 160   size_t unallocated_capacity() const            { return max_capacity() - allocated_capacity(); }
 161 
 162 private:
 163   size_t heap_unallocated_capacity() const;
 164 
 165 public:
 166   // Debugging
 167   void verify();
 168   void print()  PRODUCT_RETURN;
 169 };
 170 
 171 #endif // SHARE_VM_MEMORY_HEAP_HPP