1 /*
   2  * Copyright (c) 2012, 2013, 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 #ifndef SHARE_VM_MEMORY_METACHUNK_HPP
  25 #define SHARE_VM_MEMORY_METACHUNK_HPP
  26 
  27 #include "memory/allocation.hpp"
  28 #include "utilities/debug.hpp"
  29 #include "utilities/globalDefinitions.hpp"
  30 
  31 class VirtualSpaceNode;
  32 
  33 // Super class of Metablock and Metachunk to allow them to
  34 // be put on the FreeList and in the BinaryTreeDictionary.
  35 template <class T>
  36 class Metabase VALUE_OBJ_CLASS_SPEC {
  37   size_t _word_size;
  38   T*     _next;
  39   T*     _prev;
  40 
  41  protected:
  42   Metabase(size_t word_size) : _word_size(word_size), _next(NULL), _prev(NULL) {}
  43 
  44  public:
  45   T* next() const         { return _next; }
  46   T* prev() const         { return _prev; }
  47   void set_next(T* v)     { _next = v; assert(v != this, "Boom");}
  48   void set_prev(T* v)     { _prev = v; assert(v != this, "Boom");}
  49   void clear_next()       { set_next(NULL); }
  50   void clear_prev()       { set_prev(NULL); }
  51 
  52   size_t size() const volatile { return _word_size; }
  53   void set_size(size_t v) { _word_size = v; }
  54 
  55   void link_next(T* ptr)  { set_next(ptr); }
  56   void link_prev(T* ptr)  { set_prev(ptr); }
  57   void link_after(T* ptr) {
  58     link_next(ptr);
  59     if (ptr != NULL) ptr->link_prev((T*)this);
  60   }
  61 
  62   uintptr_t* end() const        { return ((uintptr_t*) this) + size(); }
  63 
  64   bool cantCoalesce() const     { return false; }
  65 
  66   // Debug support
  67 #ifdef ASSERT
  68   void* prev_addr() const { return (void*)&_prev; }
  69   void* next_addr() const { return (void*)&_next; }
  70   void* size_addr() const { return (void*)&_word_size; }
  71 #endif
  72   bool verify_chunk_in_free_list(T* tc) const { return true; }
  73   bool verify_par_locked() { return true; }
  74 
  75   void assert_is_mangled() const {/* Don't check "\*/}
  76 
  77   bool is_free()                 { return true; }
  78 };
  79 
  80 //  Metachunk - Quantum of allocation from a Virtualspace
  81 //    Metachunks are reused (when freed are put on a global freelist) and
  82 //    have no permanent association to a SpaceManager.
  83 
  84 //            +--------------+ <- end    --+       --+
  85 //            |              |             |         |
  86 //            |              |             | free    |
  87 //            |              |             |         |
  88 //            |              |             |         | size | capacity
  89 //            |              |             |         |
  90 //            |              | <- top   -- +         |
  91 //            |              |             |         |
  92 //            |              |             | used    |
  93 //            |              |             |         |
  94 //            |              |             |         |
  95 //            +--------------+ <- bottom --+       --+
  96 
  97 class Metachunk : public Metabase<Metachunk> {
  98   friend class TestMetachunk;
  99   // The VirtualSpaceNode containing this chunk.
 100   VirtualSpaceNode* _container;
 101 
 102   // Current allocation top.
 103   MetaWord* _top;
 104 
 105   DEBUG_ONLY(bool _is_tagged_free;)
 106 
 107   MetaWord* initial_top() const { return (MetaWord*)this + overhead(); }
 108   MetaWord* top() const         { return _top; }
 109 
 110  public:
 111   // Metachunks are allocated out of a MetadataVirtualSpace and
 112   // and use some of its space to describe itself (plus alignment
 113   // considerations).  Metadata is allocated in the rest of the chunk.
 114   // This size is the overhead of maintaining the Metachunk within
 115   // the space.
 116 
 117   // Alignment of each allocation in the chunks.
 118   static size_t object_alignment();
 119 
 120   // Size of the Metachunk header, including alignment.
 121   static size_t overhead();
 122 
 123   Metachunk(size_t word_size , VirtualSpaceNode* container);
 124 
 125   MetaWord* allocate(size_t word_size);
 126 
 127   VirtualSpaceNode* container() const { return _container; }
 128 
 129   MetaWord* bottom() const { return (MetaWord*) this; }
 130 
 131   // Reset top to bottom so chunk can be reused.
 132   void reset_empty() { _top = initial_top(); clear_next(); clear_prev(); }
 133   bool is_empty() { return _top == initial_top(); }
 134 
 135   // used (has been allocated)
 136   // free (available for future allocations)
 137   size_t word_size() const { return size(); }
 138   size_t used_word_size() const;
 139   size_t free_word_size() const;
 140 
 141 #ifdef ASSERT
 142   bool is_tagged_free() { return _is_tagged_free; }
 143   void set_is_tagged_free(bool v) { _is_tagged_free = v; }
 144 #endif
 145 
 146   bool contains(const void* ptr) { return bottom() <= ptr && ptr < _top; }
 147 
 148 #ifndef PRODUCT
 149   static const size_t metadata_chunk_initialize = 0xf7f7f7f7;
 150 
 151   void mangle(juint wordValue = metadata_chunk_initialize);
 152 #endif
 153 
 154   void print_on(outputStream* st) const;
 155   void verify();
 156 };
 157 
 158 // Metablock is the unit of allocation from a Chunk.
 159 //
 160 // A Metablock may be reused by its SpaceManager but are never moved between
 161 // SpaceManagers.  There is no explicit link to the Metachunk
 162 // from which it was allocated.  Metablock may be deallocated and
 163 // put on a freelist but the space is never freed, rather
 164 // the Metachunk it is a part of will be deallocated when it's
 165 // associated class loader is collected.
 166 
 167 class Metablock : public Metabase<Metablock> {
 168   friend class VMStructs;
 169  public:
 170   Metablock(size_t word_size) : Metabase<Metablock>(word_size) {}
 171 };
 172 
 173 #endif  // SHARE_VM_MEMORY_METACHUNK_HPP