1 /*
2 * Copyright (c) 2001, 2008, 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 /*
26 * A binary tree based search structure for free blocks.
27 * This is currently used in the Concurrent Mark&Sweep implementation.
28 */
29
30 // A TreeList is a FreeList which can be used to maintain a
31 // binary tree of free lists.
32
33 class TreeChunk;
34 class BinaryTreeDictionary;
35 class AscendTreeCensusClosure;
36 class DescendTreeCensusClosure;
37 class DescendTreeSearchClosure;
38
39 class TreeList: public FreeList {
40 friend class TreeChunk;
41 friend class BinaryTreeDictionary;
42 friend class AscendTreeCensusClosure;
43 friend class DescendTreeCensusClosure;
44 friend class DescendTreeSearchClosure;
45
46 protected:
47 TreeList* parent() const { return _parent; }
48 TreeList* left() const { return _left; }
49 TreeList* right() const { return _right; }
50
51 // Accessors for links in tree.
52
53 void setLeft(TreeList* tl) {
54 _left = tl;
55 if (tl != NULL)
56 tl->setParent(this);
57 }
58 void setRight(TreeList* tl) {
59 _right = tl;
60 if (tl != NULL)
61 tl->setParent(this);
62 }
63 void setParent(TreeList* tl) { _parent = tl; }
64
65 void clearLeft() { _left = NULL; }
66 void clearRight() { _right = NULL; }
67 void clearParent() { _parent = NULL; }
68 void initialize() { clearLeft(); clearRight(), clearParent(); }
69
70 // For constructing a TreeList from a Tree chunk or
71 // address and size.
72 static TreeList* as_TreeList(TreeChunk* tc);
73 static TreeList* as_TreeList(HeapWord* addr, size_t size);
74
75 // Returns the head of the free list as a pointer to a TreeChunk.
76 TreeChunk* head_as_TreeChunk();
77
78 // Returns the first available chunk in the free list as a pointer
79 // to a TreeChunk.
80 TreeChunk* first_available();
81
82 // Returns the block with the largest heap address amongst
83 // those in the list for this size; potentially slow and expensive,
84 // use with caution!
85 TreeChunk* largest_address();
86
87 // removeChunkReplaceIfNeeded() removes the given "tc" from the TreeList.
88 // If "tc" is the first chunk in the list, it is also the
89 // TreeList that is the node in the tree. removeChunkReplaceIfNeeded()
90 // returns the possibly replaced TreeList* for the node in
91 // the tree. It also updates the parent of the original
92 // node to point to the new node.
93 TreeList* removeChunkReplaceIfNeeded(TreeChunk* tc);
94 // See FreeList.
95 void returnChunkAtHead(TreeChunk* tc);
96 void returnChunkAtTail(TreeChunk* tc);
97 };
98
99 // A TreeChunk is a subclass of a FreeChunk that additionally
100 // maintains a pointer to the free list on which it is currently
101 // linked.
102 // A TreeChunk is also used as a node in the binary tree. This
103 // allows the binary tree to be maintained without any additional
104 // storage (the free chunks are used). In a binary tree the first
105 // chunk in the free list is also the tree node. Note that the
106 // TreeChunk has an embedded TreeList for this purpose. Because
107 // the first chunk in the list is distinguished in this fashion
108 // (also is the node in the tree), it is the last chunk to be found
109 // on the free list for a node in the tree and is only removed if
110 // it is the last chunk on the free list.
111
112 class TreeChunk : public FreeChunk {
113 friend class TreeList;
114 TreeList* _list;
115 TreeList _embedded_list; // if non-null, this chunk is on _list
116 protected:
117 TreeList* embedded_list() const { return (TreeList*) &_embedded_list; }
118 void set_embedded_list(TreeList* v) { _embedded_list = *v; }
119 public:
120 TreeList* list() { return _list; }
121 void set_list(TreeList* v) { _list = v; }
122 static TreeChunk* as_TreeChunk(FreeChunk* fc);
123 // Initialize fields in a TreeChunk that should be
124 // initialized when the TreeChunk is being added to
125 // a free list in the tree.
126 void initialize() { embedded_list()->initialize(); }
127
128 // debugging
129 void verifyTreeChunkList() const;
130 };
131
132 const size_t MIN_TREE_CHUNK_SIZE = sizeof(TreeChunk)/HeapWordSize;
133
134 class BinaryTreeDictionary: public FreeBlockDictionary {
135 friend class VMStructs;
136 bool _splay;
137 size_t _totalSize;
138 size_t _totalFreeBlocks;
139 TreeList* _root;
140
141 // private accessors
142 bool splay() const { return _splay; }
143 void set_splay(bool v) { _splay = v; }
144 size_t totalSize() const { return _totalSize; }
145 void set_totalSize(size_t v) { _totalSize = v; }
146 virtual void inc_totalSize(size_t v);
147 virtual void dec_totalSize(size_t v);
148 size_t totalFreeBlocks() const { return _totalFreeBlocks; }
149 void set_totalFreeBlocks(size_t v) { _totalFreeBlocks = v; }
150 TreeList* root() const { return _root; }
151 void set_root(TreeList* v) { _root = v; }
152
153 // Remove a chunk of size "size" or larger from the tree and
154 // return it. If the chunk
155 // is the last chunk of that size, remove the node for that size
156 // from the tree.
157 TreeChunk* getChunkFromTree(size_t size, Dither dither, bool splay);
158 // Return a list of the specified size or NULL from the tree.
159 // The list is not removed from the tree.
160 TreeList* findList (size_t size) const;
161 // Remove this chunk from the tree. If the removal results
162 // in an empty list in the tree, remove the empty list.
163 TreeChunk* removeChunkFromTree(TreeChunk* tc);
164 // Remove the node in the trees starting at tl that has the
165 // minimum value and return it. Repair the tree as needed.
166 TreeList* removeTreeMinimum(TreeList* tl);
167 void semiSplayStep(TreeList* tl);
168 // Add this free chunk to the tree.
169 void insertChunkInTree(FreeChunk* freeChunk);
170 public:
171 void verifyTree() const;
172 // verify that the given chunk is in the tree.
173 bool verifyChunkInFreeLists(FreeChunk* tc) const;
174 private:
175 void verifyTreeHelper(TreeList* tl) const;
176 static size_t verifyPrevFreePtrs(TreeList* tl);
177
178 // Returns the total number of chunks in the list.
179 size_t totalListLength(TreeList* tl) const;
180 // Returns the total number of words in the chunks in the tree
181 // starting at "tl".
182 size_t totalSizeInTree(TreeList* tl) const;
183 // Returns the sum of the square of the size of each block
184 // in the tree starting at "tl".
185 double sum_of_squared_block_sizes(TreeList* const tl) const;
186 // Returns the total number of free blocks in the tree starting
187 // at "tl".
188 size_t totalFreeBlocksInTree(TreeList* tl) const;
189 size_t numFreeBlocks() const;
190 size_t treeHeight() const;
191 size_t treeHeightHelper(TreeList* tl) const;
192 size_t totalNodesInTree(TreeList* tl) const;
193 size_t totalNodesHelper(TreeList* tl) const;
194
195 public:
196 // Constructor
197 BinaryTreeDictionary(MemRegion mr, bool splay = false);
198
199 // Reset the dictionary to the initial conditions with
200 // a single free chunk.
201 void reset(MemRegion mr);
202 void reset(HeapWord* addr, size_t size);
203 // Reset the dictionary to be empty.
204 void reset();
205
206 // Return a chunk of size "size" or greater from
207 // the tree.
208 // want a better dynamic splay strategy for the future.
209 FreeChunk* getChunk(size_t size, Dither dither) {
210 verify_par_locked();
211 FreeChunk* res = getChunkFromTree(size, dither, splay());
212 assert(res == NULL || res->isFree(),
213 "Should be returning a free chunk");
214 return res;
215 }
216
217 void returnChunk(FreeChunk* chunk) {
218 verify_par_locked();
219 insertChunkInTree(chunk);
220 }
221
222 void removeChunk(FreeChunk* chunk) {
223 verify_par_locked();
224 removeChunkFromTree((TreeChunk*)chunk);
225 assert(chunk->isFree(), "Should still be a free chunk");
226 }
227
228 size_t maxChunkSize() const;
229 size_t totalChunkSize(debug_only(const Mutex* lock)) const {
230 debug_only(
231 if (lock != NULL && lock->owned_by_self()) {
232 assert(totalSizeInTree(root()) == totalSize(),
233 "_totalSize inconsistency");
234 }
235 )
236 return totalSize();
237 }
238
239 size_t minSize() const {
240 return MIN_TREE_CHUNK_SIZE;
241 }
242
243 double sum_of_squared_block_sizes() const {
244 return sum_of_squared_block_sizes(root());
245 }
246
247 FreeChunk* find_chunk_ends_at(HeapWord* target) const;
248
249 // Find the list with size "size" in the binary tree and update
250 // the statistics in the list according to "split" (chunk was
251 // split or coalesce) and "birth" (chunk was added or removed).
252 void dictCensusUpdate(size_t size, bool split, bool birth);
253 // Return true if the dictionary is overpopulated (more chunks of
254 // this size than desired) for size "size".
255 bool coalDictOverPopulated(size_t size);
256 // Methods called at the beginning of a sweep to prepare the
257 // statistics for the sweep.
258 void beginSweepDictCensus(double coalSurplusPercent,
259 float inter_sweep_current,
260 float inter_sweep_estimate,
261 float intra_sweep_estimate);
262 // Methods called after the end of a sweep to modify the
263 // statistics for the sweep.
264 void endSweepDictCensus(double splitSurplusPercent);
265 // Return the largest free chunk in the tree.
266 FreeChunk* findLargestDict() const;
267 // Accessors for statistics
268 void setTreeSurplus(double splitSurplusPercent);
269 void setTreeHints(void);
270 // Reset statistics for all the lists in the tree.
271 void clearTreeCensus(void);
272 // Print the statistcis for all the lists in the tree. Also may
273 // print out summaries.
274 void printDictCensus(void) const;
275 void print_free_lists(outputStream* st) const;
276
277 // For debugging. Returns the sum of the _returnedBytes for
278 // all lists in the tree.
279 size_t sumDictReturnedBytes() PRODUCT_RETURN0;
280 // Sets the _returnedBytes for all the lists in the tree to zero.
281 void initializeDictReturnedBytes() PRODUCT_RETURN;
282 // For debugging. Return the total number of chunks in the dictionary.
283 size_t totalCount() PRODUCT_RETURN0;
284
285 void reportStatistics() const;
286
287 void verify() const;
288 };