hashtable.hpp revision 12790:d6d7e5caf497
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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 34// This is a generic hashtable, designed to be used for the symbol 35// and string tables. 36// 37// It is implemented as an open hash table with a fixed number of buckets. 38// 39// %note: 40// - TableEntrys are allocated in blocks to reduce the space overhead. 41 42 43 44template <MEMFLAGS F> class BasicHashtableEntry : public CHeapObj<F> { 45 friend class VMStructs; 46private: 47 unsigned int _hash; // 32-bit hash for item 48 49 // Link to next element in the linked list for this bucket. EXCEPT 50 // bit 0 set indicates that this entry is shared and must not be 51 // unlinked from the table. Bit 0 is set during the dumping of the 52 // archive. Since shared entries are immutable, _next fields in the 53 // shared entries will not change. New entries will always be 54 // unshared and since pointers are align, bit 0 will always remain 0 55 // with no extra effort. 56 BasicHashtableEntry<F>* _next; 57 58 // Windows IA64 compiler requires subclasses to be able to access these 59protected: 60 // Entry objects should not be created, they should be taken from the 61 // free list with BasicHashtable.new_entry(). 62 BasicHashtableEntry() { ShouldNotReachHere(); } 63 // Entry objects should not be destroyed. They should be placed on 64 // the free list instead with BasicHashtable.free_entry(). 65 ~BasicHashtableEntry() { ShouldNotReachHere(); } 66 67public: 68 69 unsigned int hash() const { return _hash; } 70 void set_hash(unsigned int hash) { _hash = hash; } 71 unsigned int* hash_addr() { return &_hash; } 72 73 static BasicHashtableEntry<F>* make_ptr(BasicHashtableEntry<F>* p) { 74 return (BasicHashtableEntry*)((intptr_t)p & -2); 75 } 76 77 BasicHashtableEntry<F>* next() const { 78 return make_ptr(_next); 79 } 80 81 void set_next(BasicHashtableEntry<F>* next) { 82 _next = next; 83 } 84 85 BasicHashtableEntry<F>** next_addr() { 86 return &_next; 87 } 88 89 bool is_shared() const { 90 return ((intptr_t)_next & 1) != 0; 91 } 92 93 void set_shared() { 94 _next = (BasicHashtableEntry<F>*)((intptr_t)_next | 1); 95 } 96}; 97 98 99 100template <class T, MEMFLAGS F> class HashtableEntry : public BasicHashtableEntry<F> { 101 friend class VMStructs; 102private: 103 T _literal; // ref to item in table. 104 105public: 106 // Literal 107 T literal() const { return _literal; } 108 T* literal_addr() { return &_literal; } 109 void set_literal(T s) { _literal = s; } 110 111 HashtableEntry* next() const { 112 return (HashtableEntry*)BasicHashtableEntry<F>::next(); 113 } 114 HashtableEntry** next_addr() { 115 return (HashtableEntry**)BasicHashtableEntry<F>::next_addr(); 116 } 117}; 118 119 120 121template <MEMFLAGS F> class HashtableBucket : public CHeapObj<F> { 122 friend class VMStructs; 123private: 124 // Instance variable 125 BasicHashtableEntry<F>* _entry; 126 127#ifdef ASSERT 128private: 129 unsigned _hits; 130public: 131 unsigned hits() { return _hits; } 132 void count_hit() { _hits++; } 133#endif 134 135public: 136 // Accessing 137 void clear() { _entry = NULL; DEBUG_ONLY(_hits = 0); } 138 139 // The following methods use order access methods to avoid race 140 // conditions in multiprocessor systems. 141 BasicHashtableEntry<F>* get_entry() const; 142 void set_entry(BasicHashtableEntry<F>* l); 143 144 // The following method is not MT-safe and must be done under lock. 145 BasicHashtableEntry<F>** entry_addr() { return &_entry; } 146 147}; 148 149 150template <MEMFLAGS F> class BasicHashtable : public CHeapObj<F> { 151 friend class VMStructs; 152 153public: 154 BasicHashtable(int table_size, int entry_size); 155 BasicHashtable(int table_size, int entry_size, 156 HashtableBucket<F>* buckets, int number_of_entries); 157 158 // Sharing support. 159 void copy_buckets(char** top, char* end); 160 void copy_table(char** top, char* end); 161 162 // Bucket handling 163 int hash_to_index(unsigned int full_hash) const { 164 int h = full_hash % _table_size; 165 assert(h >= 0 && h < _table_size, "Illegal hash value"); 166 return h; 167 } 168 169 // Reverse the order of elements in each of the buckets. 170 void reverse(); 171 172private: 173 // Instance variables 174 int _table_size; 175 HashtableBucket<F>* _buckets; 176 BasicHashtableEntry<F>* volatile _free_list; 177 char* _first_free_entry; 178 char* _end_block; 179 int _entry_size; 180 volatile int _number_of_entries; 181 182protected: 183 184#ifdef ASSERT 185 bool _lookup_warning; 186 mutable int _lookup_count; 187 mutable int _lookup_length; 188 bool verify_lookup_length(double load, const char *table_name); 189#endif 190 191 void initialize(int table_size, int entry_size, int number_of_entries); 192 193 // Accessor 194 int entry_size() const { return _entry_size; } 195 196 // The following method is MT-safe and may be used with caution. 197 BasicHashtableEntry<F>* bucket(int i) const; 198 199 // The following method is not MT-safe and must be done under lock. 200 BasicHashtableEntry<F>** bucket_addr(int i) { return _buckets[i].entry_addr(); } 201 202 // Attempt to get an entry from the free list 203 BasicHashtableEntry<F>* new_entry_free_list(); 204 205 // Table entry management 206 BasicHashtableEntry<F>* new_entry(unsigned int hashValue); 207 208 // Used when moving the entry to another table 209 // Clean up links, but do not add to free_list 210 void unlink_entry(BasicHashtableEntry<F>* entry) { 211 entry->set_next(NULL); 212 --_number_of_entries; 213 } 214 215 // Move over freelist and free block for allocation 216 void copy_freelist(BasicHashtable* src) { 217 _free_list = src->_free_list; 218 src->_free_list = NULL; 219 _first_free_entry = src->_first_free_entry; 220 src->_first_free_entry = NULL; 221 _end_block = src->_end_block; 222 src->_end_block = NULL; 223 } 224 225 // Free the buckets in this hashtable 226 void free_buckets(); 227 228 // Helper data structure containing context for the bucket entry unlink process, 229 // storing the unlinked buckets in a linked list. 230 // Also avoids the need to pass around these four members as parameters everywhere. 231 struct BucketUnlinkContext { 232 int _num_processed; 233 int _num_removed; 234 // Head and tail pointers for the linked list of removed entries. 235 BasicHashtableEntry<F>* _removed_head; 236 BasicHashtableEntry<F>* _removed_tail; 237 238 BucketUnlinkContext() : _num_processed(0), _num_removed(0), _removed_head(NULL), _removed_tail(NULL) { 239 } 240 241 void free_entry(BasicHashtableEntry<F>* entry); 242 }; 243 // Add of bucket entries linked together in the given context to the global free list. This method 244 // is mt-safe wrt. to other calls of this method. 245 void bulk_free_entries(BucketUnlinkContext* context); 246public: 247 int table_size() { return _table_size; } 248 void set_entry(int index, BasicHashtableEntry<F>* entry); 249 250 void add_entry(int index, BasicHashtableEntry<F>* entry); 251 252 void free_entry(BasicHashtableEntry<F>* entry); 253 254 int number_of_entries() { return _number_of_entries; } 255 256 void verify() PRODUCT_RETURN; 257 258#ifdef ASSERT 259 void bucket_count_hit(int i) const { 260 _buckets[i].count_hit(); 261 } 262 unsigned bucket_hits(int i) const { 263 return _buckets[i].hits(); 264 } 265#endif 266}; 267 268 269template <class T, MEMFLAGS F> class Hashtable : public BasicHashtable<F> { 270 friend class VMStructs; 271 272public: 273 Hashtable(int table_size, int entry_size) 274 : BasicHashtable<F>(table_size, entry_size) { } 275 276 Hashtable(int table_size, int entry_size, 277 HashtableBucket<F>* buckets, int number_of_entries) 278 : BasicHashtable<F>(table_size, entry_size, buckets, number_of_entries) { } 279 280 // Debugging 281 void print() PRODUCT_RETURN; 282 283 // Reverse the order of elements in each of the buckets. Hashtable 284 // entries which refer to objects at a lower address than 'boundary' 285 // are separated from those which refer to objects at higher 286 // addresses, and appear first in the list. 287 void reverse(void* boundary = NULL); 288 289protected: 290 291 unsigned int compute_hash(Symbol* name) { 292 return (unsigned int) name->identity_hash(); 293 } 294 295 int index_for(Symbol* name) { 296 return this->hash_to_index(compute_hash(name)); 297 } 298 299 // Table entry management 300 HashtableEntry<T, F>* new_entry(unsigned int hashValue, T obj); 301 302 // The following method is MT-safe and may be used with caution. 303 HashtableEntry<T, F>* bucket(int i) const { 304 return (HashtableEntry<T, F>*)BasicHashtable<F>::bucket(i); 305 } 306 307 // The following method is not MT-safe and must be done under lock. 308 HashtableEntry<T, F>** bucket_addr(int i) { 309 return (HashtableEntry<T, F>**)BasicHashtable<F>::bucket_addr(i); 310 } 311 312}; 313 314template <class T, MEMFLAGS F> class RehashableHashtable : public Hashtable<T, F> { 315 protected: 316 317 enum { 318 rehash_count = 100, 319 rehash_multiple = 60 320 }; 321 322 // Check that the table is unbalanced 323 bool check_rehash_table(int count); 324 325 public: 326 RehashableHashtable(int table_size, int entry_size) 327 : Hashtable<T, F>(table_size, entry_size) { } 328 329 RehashableHashtable(int table_size, int entry_size, 330 HashtableBucket<F>* buckets, int number_of_entries) 331 : Hashtable<T, F>(table_size, entry_size, buckets, number_of_entries) { } 332 333 334 // Function to move these elements into the new table. 335 void move_to(RehashableHashtable<T, F>* new_table); 336 static bool use_alternate_hashcode() { return _seed != 0; } 337 static juint seed() { return _seed; } 338 339 static int literal_size(Symbol *symbol); 340 static int literal_size(oop oop); 341 342 // The following two are currently not used, but are needed anyway because some 343 // C++ compilers (MacOS and Solaris) force the instantiation of 344 // Hashtable<ConstantPool*, mtClass>::dump_table() even though we never call this function 345 // in the VM code. 346 static int literal_size(ConstantPool *cp) {Unimplemented(); return 0;} 347 static int literal_size(Klass *k) {Unimplemented(); return 0;} 348 349 void dump_table(outputStream* st, const char *table_name); 350 351 private: 352 static juint _seed; 353}; 354 355 356// Versions of hashtable where two handles are used to compute the index. 357 358template <class T, MEMFLAGS F> class TwoOopHashtable : public Hashtable<T, F> { 359 friend class VMStructs; 360protected: 361 TwoOopHashtable(int table_size, int entry_size) 362 : Hashtable<T, F>(table_size, entry_size) {} 363 364 TwoOopHashtable(int table_size, int entry_size, HashtableBucket<F>* t, 365 int number_of_entries) 366 : Hashtable<T, F>(table_size, entry_size, t, number_of_entries) {} 367 368public: 369 unsigned int compute_hash(const Symbol* name, const ClassLoaderData* loader_data) const { 370 unsigned int name_hash = name->identity_hash(); 371 // loader is null with CDS 372 assert(loader_data != NULL || UseSharedSpaces || DumpSharedSpaces, 373 "only allowed with shared spaces"); 374 unsigned int loader_hash = loader_data == NULL ? 0 : loader_data->identity_hash(); 375 return name_hash ^ loader_hash; 376 } 377 378 int index_for(Symbol* name, ClassLoaderData* loader_data) { 379 return this->hash_to_index(compute_hash(name, loader_data)); 380 } 381}; 382 383#endif // SHARE_VM_UTILITIES_HASHTABLE_HPP 384