1 /*
2 * Copyright (c) 2003, 2017, 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_UTILITIES_HASHTABLE_HPP
26 #define SHARE_VM_UTILITIES_HASHTABLE_HPP
27
28 #include "classfile/classLoaderData.hpp"
29 #include "memory/allocation.hpp"
30 #include "oops/oop.hpp"
31 #include "oops/symbol.hpp"
32 #include "runtime/handles.hpp"
33 #include "utilities/tableStatistics.hpp"
34
35 // This is a generic hashtable, designed to be used for the symbol
36 // and string tables.
37 //
38 // It is implemented as an open hash table with a fixed number of buckets.
39 //
40 // %note:
41 // - TableEntrys are allocated in blocks to reduce the space overhead.
42
43
44
45 template <MEMFLAGS F> class BasicHashtableEntry : public CHeapObj<F> {
46 friend class VMStructs;
47 private:
48 unsigned int _hash; // 32-bit hash for item
49
50 // Link to next element in the linked list for this bucket. EXCEPT
51 // bit 0 set indicates that this entry is shared and must not be
52 // unlinked from the table. Bit 0 is set during the dumping of the
53 // archive. Since shared entries are immutable, _next fields in the
54 // shared entries will not change. New entries will always be
55 // unshared and since pointers are align, bit 0 will always remain 0
56 // with no extra effort.
57 BasicHashtableEntry<F>* _next;
58
59 // Windows IA64 compiler requires subclasses to be able to access these
60 protected:
61 // Entry objects should not be created, they should be taken from the
62 // free list with BasicHashtable.new_entry().
63 BasicHashtableEntry() { ShouldNotReachHere(); }
64 // Entry objects should not be destroyed. They should be placed on
65 // the free list instead with BasicHashtable.free_entry().
66 ~BasicHashtableEntry() { ShouldNotReachHere(); }
67
68 public:
69
70 unsigned int hash() const { return _hash; }
71 void set_hash(unsigned int hash) { _hash = hash; }
72 unsigned int* hash_addr() { return &_hash; }
73
74 static BasicHashtableEntry<F>* make_ptr(BasicHashtableEntry<F>* p) {
75 return (BasicHashtableEntry*)((intptr_t)p & -2);
76 }
77
78 BasicHashtableEntry<F>* next() const {
79 return make_ptr(_next);
80 }
81
82 void set_next(BasicHashtableEntry<F>* next) {
83 _next = next;
84 }
85
86 BasicHashtableEntry<F>** next_addr() {
87 return &_next;
88 }
89
90 bool is_shared() const {
91 return ((intptr_t)_next & 1) != 0;
92 }
93
94 void set_shared() {
95 _next = (BasicHashtableEntry<F>*)((intptr_t)_next | 1);
96 }
97 };
98
99
100
101 template <class T, MEMFLAGS F> class HashtableEntry : public BasicHashtableEntry<F> {
102 friend class VMStructs;
103 private:
104 T _literal; // ref to item in table.
105
106 public:
107 // Literal
108 T literal() const { return _literal; }
109 T* literal_addr() { return &_literal; }
110 void set_literal(T s) { _literal = s; }
111
112 HashtableEntry* next() const {
113 return (HashtableEntry*)BasicHashtableEntry<F>::next();
114 }
115 HashtableEntry** next_addr() {
116 return (HashtableEntry**)BasicHashtableEntry<F>::next_addr();
117 }
118 };
119
120
121
122 template <MEMFLAGS F> class HashtableBucket : public CHeapObj<F> {
123 friend class VMStructs;
124 private:
125 // Instance variable
126 BasicHashtableEntry<F>* _entry;
127
128 public:
129 // Accessing
130 void clear() { _entry = NULL; }
131
132 // The following methods use order access methods to avoid race
133 // conditions in multiprocessor systems.
134 BasicHashtableEntry<F>* get_entry() const;
135 void set_entry(BasicHashtableEntry<F>* l);
136
137 // The following method is not MT-safe and must be done under lock.
138 BasicHashtableEntry<F>** entry_addr() { return &_entry; }
139
140 };
141
142
143 template <MEMFLAGS F> class BasicHashtable : public CHeapObj<F> {
144 friend class VMStructs;
145
146 public:
147 BasicHashtable(int table_size, int entry_size);
148 BasicHashtable(int table_size, int entry_size,
149 HashtableBucket<F>* buckets, int number_of_entries);
150
151 // Sharing support.
152 size_t count_bytes_for_buckets();
153 size_t count_bytes_for_table();
154 void copy_buckets(char* top, char* end);
155 void copy_table(char* top, char* end);
156
157 // Bucket handling
158 int hash_to_index(unsigned int full_hash) const {
159 int h = full_hash % _table_size;
160 assert(h >= 0 && h < _table_size, "Illegal hash value");
161 return h;
162 }
163
164 private:
165 // Instance variables
166 int _table_size;
167 HashtableBucket<F>* _buckets;
168 BasicHashtableEntry<F>* volatile _free_list;
169 char* _first_free_entry;
170 char* _end_block;
171 int _entry_size;
172 volatile int _number_of_entries;
173
174 protected:
175
176 TableRateStatistics _stats_rate;
177
178 void initialize(int table_size, int entry_size, int number_of_entries);
179
180 // Accessor
181 int entry_size() const { return _entry_size; }
182
183 // The following method is MT-safe and may be used with caution.
184 BasicHashtableEntry<F>* bucket(int i) const;
185
186 // The following method is not MT-safe and must be done under lock.
187 BasicHashtableEntry<F>** bucket_addr(int i) { return _buckets[i].entry_addr(); }
188
189 // Attempt to get an entry from the free list
190 BasicHashtableEntry<F>* new_entry_free_list();
191
192 // Table entry management
193 BasicHashtableEntry<F>* new_entry(unsigned int hashValue);
194
195 // Used when moving the entry to another table
196 // Clean up links, but do not add to free_list
197 void unlink_entry(BasicHashtableEntry<F>* entry) {
198 entry->set_next(NULL);
199 --_number_of_entries;
200 }
201
202 // Move over freelist and free block for allocation
203 void copy_freelist(BasicHashtable* src) {
204 _free_list = src->_free_list;
205 src->_free_list = NULL;
206 _first_free_entry = src->_first_free_entry;
207 src->_first_free_entry = NULL;
208 _end_block = src->_end_block;
209 src->_end_block = NULL;
210 }
211
212 // Free the buckets in this hashtable
213 void free_buckets();
214
215 // Helper data structure containing context for the bucket entry unlink process,
216 // storing the unlinked buckets in a linked list.
217 // Also avoids the need to pass around these four members as parameters everywhere.
218 struct BucketUnlinkContext {
219 int _num_processed;
220 int _num_removed;
221 // Head and tail pointers for the linked list of removed entries.
222 BasicHashtableEntry<F>* _removed_head;
223 BasicHashtableEntry<F>* _removed_tail;
224
225 BucketUnlinkContext() : _num_processed(0), _num_removed(0), _removed_head(NULL), _removed_tail(NULL) {
226 }
227
228 void free_entry(BasicHashtableEntry<F>* entry);
229 };
230 // Add of bucket entries linked together in the given context to the global free list. This method
231 // is mt-safe wrt. to other calls of this method.
232 void bulk_free_entries(BucketUnlinkContext* context);
233 public:
234 int table_size() const { return _table_size; }
235 void set_entry(int index, BasicHashtableEntry<F>* entry);
236
237 void add_entry(int index, BasicHashtableEntry<F>* entry);
238
239 void free_entry(BasicHashtableEntry<F>* entry);
240
241 int number_of_entries() const { return _number_of_entries; }
242
243 bool resize(int new_size);
244
245 template <class T> void verify_table(const char* table_name) PRODUCT_RETURN;
246 };
247
248
249 template <class T, MEMFLAGS F> class Hashtable : public BasicHashtable<F> {
250 friend class VMStructs;
251
252 public:
253 Hashtable(int table_size, int entry_size)
254 : BasicHashtable<F>(table_size, entry_size) { }
255
256 Hashtable(int table_size, int entry_size,
257 HashtableBucket<F>* buckets, int number_of_entries)
258 : BasicHashtable<F>(table_size, entry_size, buckets, number_of_entries) { }
259
260 // Debugging
261 void print() PRODUCT_RETURN;
262
263 unsigned int compute_hash(const Symbol* name) const {
264 return (unsigned int) name->identity_hash();
265 }
266
267 int index_for(const Symbol* name) const {
268 return this->hash_to_index(compute_hash(name));
269 }
270
271 TableStatistics statistics_calculate(T (*literal_load_barrier)(HashtableEntry<T, F>*) = NULL);
272 void print_table_statistics(outputStream* st, const char *table_name, T (*literal_load_barrier)(HashtableEntry<T, F>*) = NULL);
273
274 protected:
275
276 // Table entry management
277 HashtableEntry<T, F>* new_entry(unsigned int hashValue, T obj);
278 // Don't create and use freelist of HashtableEntry.
279 HashtableEntry<T, F>* allocate_new_entry(unsigned int hashValue, T obj);
280
281 // The following method is MT-safe and may be used with caution.
282 HashtableEntry<T, F>* bucket(int i) const {
283 return (HashtableEntry<T, F>*)BasicHashtable<F>::bucket(i);
284 }
285
286 // The following method is not MT-safe and must be done under lock.
287 HashtableEntry<T, F>** bucket_addr(int i) {
288 return (HashtableEntry<T, F>**)BasicHashtable<F>::bucket_addr(i);
289 }
290 };
291
292 template <class T, MEMFLAGS F> class RehashableHashtable : public Hashtable<T, F> {
293 friend class VMStructs;
294 protected:
295
296 enum {
297 rehash_count = 100,
298 rehash_multiple = 60
299 };
300
301 // Check that the table is unbalanced
302 bool check_rehash_table(int count);
303
304 public:
305 RehashableHashtable(int table_size, int entry_size)
306 : Hashtable<T, F>(table_size, entry_size) { }
307
308 RehashableHashtable(int table_size, int entry_size,
309 HashtableBucket<F>* buckets, int number_of_entries)
310 : Hashtable<T, F>(table_size, entry_size, buckets, number_of_entries) { }
311
312
313 // Function to move these elements into the new table.
314 void move_to(RehashableHashtable<T, F>* new_table);
315 static bool use_alternate_hashcode();
316 static juint seed();
317
318 private:
319 static juint _seed;
320 };
321
322 template <class T, MEMFLAGS F> juint RehashableHashtable<T, F>::_seed = 0;
323 template <class T, MEMFLAGS F> juint RehashableHashtable<T, F>::seed() { return _seed; };
324 template <class T, MEMFLAGS F> bool RehashableHashtable<T, F>::use_alternate_hashcode() { return _seed != 0; };
325
326 #endif // SHARE_VM_UTILITIES_HASHTABLE_HPP