1 /*
   2  * Copyright (c) 2012, 2018, 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.
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   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
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  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
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  24 #ifndef SHARE_VM_MEMORY_METACHUNK_HPP
  25 #define SHARE_VM_MEMORY_METACHUNK_HPP
  26 
  27 #include "memory/metaspace/metabase.hpp"
  28 #include "memory/metaspace/metaspaceCommon.hpp"
  29 #include "utilities/debug.hpp"
  30 #include "utilities/globalDefinitions.hpp"
  31 
  32 class MetachunkTest;
  33 
  34 namespace metaspace {
  35 namespace internals {
  36 
  37 class VirtualSpaceNode;
  38 
  39 //  Metachunk - Quantum of allocation from a Virtualspace
  40 //    Metachunks are reused (when freed are put on a global freelist) and
  41 //    have no permanent association to a SpaceManager.
  42 
  43 //            +--------------+ <- end    --+       --+
  44 //            |              |             |         |
  45 //            |              |             | free    |
  46 //            |              |             |         |
  47 //            |              |             |         | size | capacity
  48 //            |              |             |         |
  49 //            |              | <- top   -- +         |
  50 //            |              |             |         |
  51 //            |              |             | used    |
  52 //            |              |             |         |
  53 //            |              |             |         |
  54 //            +--------------+ <- bottom --+       --+
  55 
  56 enum ChunkOrigin {
  57   // Chunk normally born (via take_from_committed)
  58   origin_normal = 1,
  59   // Chunk was born as padding chunk
  60   origin_pad = 2,
  61   // Chunk was born as leftover chunk in VirtualSpaceNode::retire
  62   origin_leftover = 3,
  63   // Chunk was born as result of a merge of smaller chunks
  64   origin_merge = 4,
  65   // Chunk was born as result of a split of a larger chunk
  66   origin_split = 5,
  67 
  68   origin_minimum = origin_normal,
  69   origin_maximum = origin_split,
  70   origins_count = origin_maximum + 1
  71 };
  72 
  73 inline bool is_valid_chunkorigin(ChunkOrigin origin) {
  74   return origin == origin_normal ||
  75     origin == origin_pad ||
  76     origin == origin_leftover ||
  77     origin == origin_merge ||
  78     origin == origin_split;
  79 }
  80 
  81 class Metachunk : public Metabase<Metachunk> {
  82 
  83   friend class ::MetachunkTest;
  84 
  85   // The VirtualSpaceNode containing this chunk.
  86   VirtualSpaceNode* const _container;
  87 
  88   // Current allocation top.
  89   MetaWord* _top;
  90 
  91   // A 32bit sentinel for debugging purposes.
  92   enum { CHUNK_SENTINEL = 0x4d4554EF,  // "MET"
  93          CHUNK_SENTINEL_INVALID = 0xFEEEEEEF
  94   };
  95 
  96   uint32_t _sentinel;
  97 
  98   const ChunkIndex _chunk_type;
  99   const bool _is_class;
 100   // Whether the chunk is free (in freelist) or in use by some class loader.
 101   bool _is_tagged_free;
 102 
 103   ChunkOrigin _origin;
 104   int _use_count;
 105 
 106   MetaWord* initial_top() const { return (MetaWord*)this + overhead(); }
 107   MetaWord* top() const         { return _top; }
 108 
 109  public:
 110   // Metachunks are allocated out of a MetadataVirtualSpace and
 111   // and use some of its space to describe itself (plus alignment
 112   // considerations).  Metadata is allocated in the rest of the chunk.
 113   // This size is the overhead of maintaining the Metachunk within
 114   // the space.
 115 
 116   // Alignment of each allocation in the chunks.
 117   static size_t object_alignment();
 118 
 119   // Size of the Metachunk header, in words, including alignment.
 120   static size_t overhead();
 121 
 122   Metachunk(ChunkIndex chunktype, bool is_class, size_t word_size, VirtualSpaceNode* container);
 123 
 124   MetaWord* allocate(size_t word_size);
 125 
 126   VirtualSpaceNode* container() const { return _container; }
 127 
 128   MetaWord* bottom() const { return (MetaWord*) this; }
 129 
 130   // Reset top to bottom so chunk can be reused.
 131   void reset_empty() { _top = initial_top(); clear_next(); clear_prev(); }
 132   bool is_empty() { return _top == initial_top(); }
 133 
 134   // used (has been allocated)
 135   // free (available for future allocations)
 136   size_t word_size() const { return size(); }
 137   size_t used_word_size() const;
 138   size_t free_word_size() const;
 139 
 140   bool is_tagged_free() { return _is_tagged_free; }
 141   void set_is_tagged_free(bool v) { _is_tagged_free = v; }
 142 
 143   bool contains(const void* ptr) { return bottom() <= ptr && ptr < _top; }
 144 
 145   void print_on(outputStream* st) const;
 146 
 147   bool is_valid_sentinel() const        { return _sentinel == CHUNK_SENTINEL; }
 148   void remove_sentinel()                { _sentinel = CHUNK_SENTINEL_INVALID; }
 149 
 150   int get_use_count() const             { return _use_count; }
 151   void inc_use_count()                  { _use_count ++; }
 152 
 153   ChunkOrigin get_origin() const        { return _origin; }
 154   void set_origin(ChunkOrigin orig)     { _origin = orig; }
 155 
 156   ChunkIndex get_chunk_type() const     { return _chunk_type; }
 157   bool is_class() const                 { return _is_class; }
 158 
 159   DEBUG_ONLY(void mangle(juint word_value);)
 160   DEBUG_ONLY(void verify() const;)
 161 
 162 };
 163 
 164 
 165 // Helper function that does a bunch of checks for a chunk.
 166 DEBUG_ONLY(void do_verify_chunk(Metachunk* chunk);)
 167 
 168 // Given a Metachunk, update its in-use information (both in the
 169 // chunk and the occupancy map).
 170 void do_update_in_use_info_for_chunk(Metachunk* chunk, bool inuse);
 171 
 172 } // namespace metaspace
 173 } // namespace internals
 174 
 175 #endif  // SHARE_VM_MEMORY_METACHUNK_HPP