1 /* 2 * Copyright (c) 2018, 2019, 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_MEMORY_METASPACE_CHUNKTREE_HPP 26 #define SHARE_MEMORY_METASPACE_CHUNKTREE_HPP 27 28 #include "memory/allocation.hpp" 29 #include "memory/metaspace/abstractPool.hpp" 30 #include "memory/metaspace/chunkLevel.hpp" 31 #include "memory/metaspace/metachunk.hpp" 32 33 namespace metaspace { 34 35 // Chunks live in a binary tree. 36 // 37 38 class ChunkClosure { 39 public: 40 // Return false to cancel traversal. 41 virtual bool do_chunk(Metachunk* chunk) = 0; 42 }; 43 44 45 class ChunkTree : public CHeapObj<mtClass> { 46 47 typedef u2 ref_t; 48 49 // Root is either a direct pointer to a Metachunk* (in that case, a root chunk of max. size) 50 // or a pointer to a node. 51 ref_t _root; 52 53 struct btnode_t { 54 55 ref_t parent; 56 ref_t child[2]; 57 58 }; 59 60 typedef AbstractPool<btnode_t, ref_t> NodePoolType; 61 typedef AbstractPool<Metachunk, ref_t> ChunkPoolType; 62 NodePoolType _nodePool; 63 ChunkPoolType _chunkPool; 64 65 // The upper two bits of a reference encode information about it. 66 // bit 0,1: 00 - reference is a btnode_t 67 // 10 - reference is a free chunk 68 // 11 - reference is a chunk in use. 69 // This also means a reference has to get by with 14 bits. Which covers 16K, which is enough for both 70 // chunk headers and nodes within one root chunk area. 71 static const u2 highest_possible_index = (1 << 14) - 1; 72 static const u2 node_marker = 0; 73 static const u2 free_chunk_marker = 2; 74 static const u2 used_chunk_marker = 3; 75 76 static u2 get_raw_index_from_reference(ref_t ref) { return 0x3FFF & ref; } 77 static u2 get_info_from_reference(ref_t ref) { return 0xc000 & ref; } 78 79 static u2 encode_reference(u2 raw_idx, u2 info) { 80 assert(raw_idx <= highest_possible_index, "invalid index"); 81 return (info << 14) | raw_idx; 82 } 83 84 #ifdef ASSERT 85 static bool reference_is_node(ref_t ref) { return get_info_from_reference(ref) == node_marker; } 86 static bool reference_is_chunk(ref_t ref) { u2 i = get_info_from_reference(ref); return i == free_chunk_marker || i == used_chunk_marker; } 87 static bool reference_is_used_chunk(ref_t ref) { return get_info_from_reference(ref) == used_chunk_marker; } 88 89 void check_is_valid_node_ref(ref_t ref) { assert(resolve_reference_to_node(ref) != NULL, "invalid node ref"); } 90 void check_is_valid_chunk_ref(ref_t ref) { assert(resolve_reference_to_chunk(ref) != NULL, "invalid chunk ref"); } 91 void check_is_valid_ref(ref_t ref); 92 #endif 93 94 static bool reference_is_free_chunk(ref_t ref) { return get_info_from_reference(ref) == free_chunk_marker; } 95 96 // Given a reference we know to be a node, resolve it to the node pointer. 97 btnode_t* resolve_reference_to_node(ref_t ref) const { 98 assert(reference_is_node(ref), "Not a node ref"); 99 return _nodePool.elem_at_index(get_raw_index_from_reference(ref)); 100 } 101 102 // Allocate a new node. Node is uninitialized. 103 // Returns pointer to node, and reference in ref. 104 btnode_t* allocate_new_node() { 105 return _nodePool.allocate_element(); 106 } 107 108 // Given a node pointer, return its correctly encoded reference. 109 ref_t encode_reference_for_node(const btnode_t* n) const { 110 const u2 raw_idx = _nodePool.index_for_elem(n); 111 return encode_reference(raw_idx, node_marker); 112 } 113 114 // Release a node to the pool. 115 void release_node(btnode_t* n) { 116 _nodePool.return_element(n); 117 } 118 119 // Given a reference we know to be a chunk, resolve it to the chunk pointer. 120 Metachunk* resolve_reference_to_chunk(ref_t ref) const { 121 assert(reference_is_chunk(ref), "Not a chunk ref"); 122 return _chunkPool.elem_at_index(get_raw_index_from_reference(ref)); 123 } 124 125 // Allocate a new node. Node is uninitialized. 126 // Returns pointer to node, and reference in ref. 127 Metachunk* allocate_new_chunk() { 128 return _chunkPool.allocate_element(); 129 } 130 131 // Given a chunk pointer, return its correctly encoded reference. 132 ref_t encode_reference_for_chunk(Metachunk* c, bool is_free) const { 133 const u2 raw_idx = _chunkPool.index_for_elem(c); 134 return encode_reference(raw_idx, is_free ? free_chunk_marker : used_chunk_marker); 135 } 136 137 // Release a chunk to the pool. 138 void release_chunk(Metachunk* c) { 139 _chunkPool.return_element(c); 140 } 141 142 //// Helpers for tree traversal //// 143 144 class ConstChunkClosure; 145 bool iterate_chunks_helper(ref_t ref, ChunkClosure* cc) const; 146 147 #ifdef ASSERT 148 // Verify a life node (one which lives in the tree). 149 void verify_node(const btnode_t* n) const; 150 // Helper for verify() 151 void verify_helper(bool slow, ref_t ref, const MetaWord* p, int* num_chunks, int* num_nodes) const; 152 #endif 153 154 // Given a chunk c, split it once. 155 // 156 // The original chunk must not be part of a freelist. 157 // 158 // Returns pointer to the result chunk; updates the splinters array to return the splintered off chunk. 159 // 160 // Returns NULL if chunk cannot be split any further. 161 Metachunk* split_once(Metachunk* c, Metachunk* splinters[chklvl::NUM_CHUNK_LEVELS]); 162 163 // Given a chunk, attempt to merge it with its sibling if it is free. 164 // Returns pointer to the result chunk if successful, NULL otherwise. 165 // 166 // Returns number of merged chunks, by chunk level, in num_merged array. These numbers 167 // includes the original chunk. 168 // 169 // !!! Please note that if this method returns a non-NULL value, the 170 // original chunk will be invalid and should not be accessed anymore! !!! 171 Metachunk* merge_once(Metachunk* c, int num_merged[chklvl::NUM_CHUNK_LEVELS]); 172 173 public: 174 175 ChunkTree(); 176 virtual ~ChunkTree() {} 177 178 // Initialize: allocate a root node and a root chunk header; return the 179 // root chunk header. It will be partly initialized. 180 // Note: this just allocates a memory-less header; memory itself is allocated inside VirtualSpaceNode. 181 Metachunk* alloc_root_chunk_header(); 182 183 // Given a chunk c, split it recursively until you get a chunk of the given target_level. 184 // 185 // The original chunk must not be part of a freelist. 186 // 187 // Returns pointer to the result chunk; returns split off chunks in splinters array. 188 // 189 // Returns NULL if chunk cannot be split at least once. 190 Metachunk* split(chklvl_t target_level, Metachunk* c, Metachunk* splinters[chklvl::NUM_CHUNK_LEVELS]); 191 192 // Given a chunk, attempt to merge it recursively with its neighboring chunks. 193 // 194 // If successful (merged at least once), returns address of 195 // the merged chunk; NULL otherwise. 196 // 197 // The merged chunks are removed from their freelist; the number of merged chunks is 198 // returned, split by level, in num_merged array. Note that these numbers does not 199 // include the original chunk. 200 // 201 // !!! Please note that if this method returns a non-NULL value, the 202 // original chunk will be invalid and should not be accessed anymore! !!! 203 Metachunk* merge(Metachunk* c, int num_merged[chklvl::NUM_CHUNK_LEVELS]); 204 205 //// tree traversal //// 206 207 // Iterate over all nodes in this tree. Returns true for complete traversal, 208 // false if traversal was cancelled. 209 bool iterate_chunks(ChunkClosure* cc) const; 210 211 212 //// Debug stuff //// 213 214 // Verify tree. If base != NULL, it should point to the location assumed 215 // to be base of the first chunk. 216 DEBUG_ONLY(void verify(bool slow, const MetaWord* base) const;) 217 218 // Returns the footprint of this tree, in words. 219 size_t memory_footprint_words() const; 220 221 222 }; 223 224 225 /////////////////////// 226 // An C-heap allocated array of chunk trees. Used to describe fragmentation over a range of multiple root chunks. 227 class ChunkTreeArray { 228 229 const MetaWord* const _base; 230 const size_t _word_size; 231 232 ChunkTree** _arr; 233 int _num; 234 235 #ifdef ASSERT 236 void check_pointer(const MetaWord* p) const { 237 assert(p >= _base && p < _base + _word_size, "Invalid pointer"); 238 } 239 #endif 240 241 int index_by_address(const MetaWord* p) const { 242 DEBUG_ONLY(check_pointer(p);) 243 return (p - _base) / chklvl::MAX_CHUNK_WORD_SIZE; 244 } 245 246 public: 247 248 // Create an array of ChunkTree objects, all initialized to NULL, covering 249 // a given memory range. Memory range must be aligned to size of root chunks. 250 ChunkTreeArray(const MetaWord* base, size_t word_size); 251 252 ~ChunkTreeArray(); 253 254 // Given a memory address into the range the trees cover, return the corresponding 255 // tree. If none existed at this position, create it. 256 ChunkTree* get_tree_by_address(const MetaWord* p) const { 257 assert(p >= _base && p < _base + _word_size, "Invalid pointer"); 258 const int idx = index_by_address(p); 259 assert(idx >= 0 && idx < _num, "Invalid index"); 260 if (_arr[idx] == NULL) { 261 _arr[idx] = new ChunkTree(); 262 } 263 return _arr[idx]; 264 } 265 266 // Iterate over all nodes in all trees. Returns true for complete traversal, 267 // false if traversal was cancelled. 268 bool iterate_chunks(ChunkClosure* cc) const; 269 270 DEBUG_ONLY(void verify(bool slow) const;) 271 272 // Returns the footprint of all trees in this array, in words. 273 size_t memory_footprint_words() const; 274 275 }; 276 277 278 } // namespace metaspace 279 280 #endif // SHARE_MEMORY_METASPACE_CHUNKTREE_HPP