hashtable.hpp revision 13169:09fbbd907028
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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 127public: 128 // Accessing 129 void clear() { _entry = NULL; } 130 131 // The following methods use order access methods to avoid race 132 // conditions in multiprocessor systems. 133 BasicHashtableEntry<F>* get_entry() const; 134 void set_entry(BasicHashtableEntry<F>* l); 135 136 // The following method is not MT-safe and must be done under lock. 137 BasicHashtableEntry<F>** entry_addr() { return &_entry; } 138 139}; 140 141 142template <MEMFLAGS F> class BasicHashtable : public CHeapObj<F> { 143 friend class VMStructs; 144 145public: 146 BasicHashtable(int table_size, int entry_size); 147 BasicHashtable(int table_size, int entry_size, 148 HashtableBucket<F>* buckets, int number_of_entries); 149 150 // Sharing support. 151 void copy_buckets(char** top, char* end); 152 void copy_table(char** top, char* end); 153 154 // Bucket handling 155 int hash_to_index(unsigned int full_hash) const { 156 int h = full_hash % _table_size; 157 assert(h >= 0 && h < _table_size, "Illegal hash value"); 158 return h; 159 } 160 161private: 162 // Instance variables 163 int _table_size; 164 HashtableBucket<F>* _buckets; 165 BasicHashtableEntry<F>* volatile _free_list; 166 char* _first_free_entry; 167 char* _end_block; 168 int _entry_size; 169 volatile int _number_of_entries; 170 171protected: 172 173 void initialize(int table_size, int entry_size, int number_of_entries); 174 175 // Accessor 176 int entry_size() const { return _entry_size; } 177 178 // The following method is MT-safe and may be used with caution. 179 BasicHashtableEntry<F>* bucket(int i) const; 180 181 // The following method is not MT-safe and must be done under lock. 182 BasicHashtableEntry<F>** bucket_addr(int i) { return _buckets[i].entry_addr(); } 183 184 // Attempt to get an entry from the free list 185 BasicHashtableEntry<F>* new_entry_free_list(); 186 187 // Table entry management 188 BasicHashtableEntry<F>* new_entry(unsigned int hashValue); 189 190 // Used when moving the entry to another table 191 // Clean up links, but do not add to free_list 192 void unlink_entry(BasicHashtableEntry<F>* entry) { 193 entry->set_next(NULL); 194 --_number_of_entries; 195 } 196 197 // Move over freelist and free block for allocation 198 void copy_freelist(BasicHashtable* src) { 199 _free_list = src->_free_list; 200 src->_free_list = NULL; 201 _first_free_entry = src->_first_free_entry; 202 src->_first_free_entry = NULL; 203 _end_block = src->_end_block; 204 src->_end_block = NULL; 205 } 206 207 // Free the buckets in this hashtable 208 void free_buckets(); 209 210 // Helper data structure containing context for the bucket entry unlink process, 211 // storing the unlinked buckets in a linked list. 212 // Also avoids the need to pass around these four members as parameters everywhere. 213 struct BucketUnlinkContext { 214 int _num_processed; 215 int _num_removed; 216 // Head and tail pointers for the linked list of removed entries. 217 BasicHashtableEntry<F>* _removed_head; 218 BasicHashtableEntry<F>* _removed_tail; 219 220 BucketUnlinkContext() : _num_processed(0), _num_removed(0), _removed_head(NULL), _removed_tail(NULL) { 221 } 222 223 void free_entry(BasicHashtableEntry<F>* entry); 224 }; 225 // Add of bucket entries linked together in the given context to the global free list. This method 226 // is mt-safe wrt. to other calls of this method. 227 void bulk_free_entries(BucketUnlinkContext* context); 228public: 229 int table_size() { return _table_size; } 230 void set_entry(int index, BasicHashtableEntry<F>* entry); 231 232 void add_entry(int index, BasicHashtableEntry<F>* entry); 233 234 void free_entry(BasicHashtableEntry<F>* entry); 235 236 int number_of_entries() { return _number_of_entries; } 237 238 template <class T> void verify_table(const char* table_name) PRODUCT_RETURN; 239}; 240 241 242template <class T, MEMFLAGS F> class Hashtable : public BasicHashtable<F> { 243 friend class VMStructs; 244 245public: 246 Hashtable(int table_size, int entry_size) 247 : BasicHashtable<F>(table_size, entry_size) { } 248 249 Hashtable(int table_size, int entry_size, 250 HashtableBucket<F>* buckets, int number_of_entries) 251 : BasicHashtable<F>(table_size, entry_size, buckets, number_of_entries) { } 252 253 // Debugging 254 void print() PRODUCT_RETURN; 255 256protected: 257 258 unsigned int compute_hash(Symbol* name) { 259 return (unsigned int) name->identity_hash(); 260 } 261 262 int index_for(Symbol* name) { 263 return this->hash_to_index(compute_hash(name)); 264 } 265 266 // Table entry management 267 HashtableEntry<T, F>* new_entry(unsigned int hashValue, T obj); 268 269 // The following method is MT-safe and may be used with caution. 270 HashtableEntry<T, F>* bucket(int i) const { 271 return (HashtableEntry<T, F>*)BasicHashtable<F>::bucket(i); 272 } 273 274 // The following method is not MT-safe and must be done under lock. 275 HashtableEntry<T, F>** bucket_addr(int i) { 276 return (HashtableEntry<T, F>**)BasicHashtable<F>::bucket_addr(i); 277 } 278 279}; 280 281template <class T, MEMFLAGS F> class RehashableHashtable : public Hashtable<T, F> { 282 friend class VMStructs; 283 protected: 284 285 enum { 286 rehash_count = 100, 287 rehash_multiple = 60 288 }; 289 290 // Check that the table is unbalanced 291 bool check_rehash_table(int count); 292 293 public: 294 RehashableHashtable(int table_size, int entry_size) 295 : Hashtable<T, F>(table_size, entry_size) { } 296 297 RehashableHashtable(int table_size, int entry_size, 298 HashtableBucket<F>* buckets, int number_of_entries) 299 : Hashtable<T, F>(table_size, entry_size, buckets, number_of_entries) { } 300 301 302 // Function to move these elements into the new table. 303 void move_to(RehashableHashtable<T, F>* new_table); 304 static bool use_alternate_hashcode() { return _seed != 0; } 305 static juint seed() { return _seed; } 306 307 static int literal_size(Symbol *symbol); 308 static int literal_size(oop oop); 309 310 // The following two are currently not used, but are needed anyway because some 311 // C++ compilers (MacOS and Solaris) force the instantiation of 312 // Hashtable<ConstantPool*, mtClass>::dump_table() even though we never call this function 313 // in the VM code. 314 static int literal_size(ConstantPool *cp) {Unimplemented(); return 0;} 315 static int literal_size(Klass *k) {Unimplemented(); return 0;} 316 317 void dump_table(outputStream* st, const char *table_name); 318 319 private: 320 static juint _seed; 321}; 322 323 324// Versions of hashtable where two handles are used to compute the index. 325 326template <class T, MEMFLAGS F> class TwoOopHashtable : public Hashtable<T, F> { 327 friend class VMStructs; 328protected: 329 TwoOopHashtable(int table_size, int entry_size) 330 : Hashtable<T, F>(table_size, entry_size) {} 331 332 TwoOopHashtable(int table_size, int entry_size, HashtableBucket<F>* t, 333 int number_of_entries) 334 : Hashtable<T, F>(table_size, entry_size, t, number_of_entries) {} 335 336public: 337 unsigned int compute_hash(const Symbol* name, const ClassLoaderData* loader_data) const { 338 unsigned int name_hash = name->identity_hash(); 339 // loader is null with CDS 340 assert(loader_data != NULL || UseSharedSpaces || DumpSharedSpaces, 341 "only allowed with shared spaces"); 342 unsigned int loader_hash = loader_data == NULL ? 0 : loader_data->identity_hash(); 343 return name_hash ^ loader_hash; 344 } 345 346 int index_for(Symbol* name, ClassLoaderData* loader_data) { 347 return this->hash_to_index(compute_hash(name, loader_data)); 348 } 349}; 350 351#endif // SHARE_VM_UTILITIES_HASHTABLE_HPP 352