1 /* 2 * Copyright (c) 2003, 2018, 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 #include "precompiled.hpp" 26 #include "classfile/altHashing.hpp" 27 #include "classfile/dictionary.hpp" 28 #include "classfile/javaClasses.inline.hpp" 29 #include "classfile/moduleEntry.hpp" 30 #include "classfile/packageEntry.hpp" 31 #include "classfile/placeholders.hpp" 32 #include "classfile/protectionDomainCache.hpp" 33 #include "classfile/stringTable.hpp" 34 #include "logging/log.hpp" 35 #include "memory/allocation.inline.hpp" 36 #include "memory/resourceArea.hpp" 37 #include "oops/oop.inline.hpp" 38 #include "oops/weakHandle.inline.hpp" 39 #include "runtime/safepoint.hpp" 40 #include "utilities/dtrace.hpp" 41 #include "utilities/hashtable.hpp" 42 #include "utilities/hashtable.inline.hpp" 43 #include "utilities/numberSeq.hpp" 44 45 46 // This hashtable is implemented as an open hash table with a fixed number of buckets. 47 48 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry_free_list() { 49 BasicHashtableEntry<F>* entry = NULL; 50 if (_free_list != NULL) { 51 entry = _free_list; 52 _free_list = _free_list->next(); 53 } 54 return entry; 55 } 56 57 // HashtableEntrys are allocated in blocks to reduce the space overhead. 58 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) { 59 BasicHashtableEntry<F>* entry = new_entry_free_list(); 60 61 if (entry == NULL) { 62 if (_first_free_entry + _entry_size >= _end_block) { 63 int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries)); 64 int len = _entry_size * block_size; 65 len = 1 << log2_int(len); // round down to power of 2 66 assert(len >= _entry_size, ""); 67 _first_free_entry = NEW_C_HEAP_ARRAY2(char, len, F, CURRENT_PC); 68 _entry_blocks->append(_first_free_entry); 69 _end_block = _first_free_entry + len; 70 } 71 entry = (BasicHashtableEntry<F>*)_first_free_entry; 72 _first_free_entry += _entry_size; 73 } 74 75 assert(_entry_size % HeapWordSize == 0, ""); 76 entry->set_hash(hashValue); 77 return entry; 78 } 79 80 81 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::new_entry(unsigned int hashValue, T obj) { 82 HashtableEntry<T, F>* entry; 83 84 entry = (HashtableEntry<T, F>*)BasicHashtable<F>::new_entry(hashValue); 85 entry->set_literal(obj); 86 return entry; 87 } 88 89 // Version of hashtable entry allocation that allocates in the C heap directly. 90 // The block allocator in BasicHashtable has less fragmentation, but the memory is not freed until 91 // the whole table is freed. Use allocate_new_entry() if you want to individually free the memory 92 // used by each entry 93 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::allocate_new_entry(unsigned int hashValue, T obj) { 94 HashtableEntry<T, F>* entry = (HashtableEntry<T, F>*) NEW_C_HEAP_ARRAY(char, this->entry_size(), F); 95 96 entry->set_hash(hashValue); 97 entry->set_literal(obj); 98 entry->set_next(NULL); 99 return entry; 100 } 101 102 template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() { 103 if (NULL != _buckets) { 104 FREE_C_HEAP_ARRAY(HashtableBucket, _buckets); 105 _buckets = NULL; 106 } 107 } 108 109 template <MEMFLAGS F> void BasicHashtable<F>::BucketUnlinkContext::free_entry(BasicHashtableEntry<F>* entry) { 110 entry->set_next(_removed_head); 111 _removed_head = entry; 112 if (_removed_tail == NULL) { 113 _removed_tail = entry; 114 } 115 _num_removed++; 116 } 117 118 template <MEMFLAGS F> void BasicHashtable<F>::bulk_free_entries(BucketUnlinkContext* context) { 119 if (context->_num_removed == 0) { 120 assert(context->_removed_head == NULL && context->_removed_tail == NULL, 121 "Zero entries in the unlink context, but elements linked from " PTR_FORMAT " to " PTR_FORMAT, 122 p2i(context->_removed_head), p2i(context->_removed_tail)); 123 return; 124 } 125 126 // MT-safe add of the list of BasicHashTableEntrys from the context to the free list. 127 BasicHashtableEntry<F>* current = _free_list; 128 while (true) { 129 context->_removed_tail->set_next(current); 130 BasicHashtableEntry<F>* old = Atomic::cmpxchg(context->_removed_head, &_free_list, current); 131 if (old == current) { 132 break; 133 } 134 current = old; 135 } 136 Atomic::add(-context->_num_removed, &_number_of_entries); 137 } 138 139 // For oops and Strings the size of the literal is interesting. For other types, nobody cares. 140 static int literal_size(ConstantPool*) { return 0; } 141 static int literal_size(Klass*) { return 0; } 142 static int literal_size(nmethod*) { return 0; } 143 144 static int literal_size(Symbol *symbol) { 145 return symbol->size() * HeapWordSize; 146 } 147 148 static int literal_size(oop obj) { 149 // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true, 150 // and the String.value array is shared by several Strings. However, starting from JDK8, 151 // the String.value array is not shared anymore. 152 if (obj == NULL) { 153 return 0; 154 } else if (obj->klass() == SystemDictionary::String_klass()) { 155 return (obj->size() + java_lang_String::value(obj)->size()) * HeapWordSize; 156 } else { 157 return obj->size(); 158 } 159 } 160 161 static int literal_size(ClassLoaderWeakHandle v) { 162 return literal_size(v.peek()); 163 } 164 165 template <MEMFLAGS F> bool BasicHashtable<F>::resize(int new_size) { 166 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 167 168 // Allocate new buckets 169 HashtableBucket<F>* buckets_new = NEW_C_HEAP_ARRAY2_RETURN_NULL(HashtableBucket<F>, new_size, F, CURRENT_PC); 170 if (buckets_new == NULL) { 171 return false; 172 } 173 174 // Clear the new buckets 175 for (int i = 0; i < new_size; i++) { 176 buckets_new[i].clear(); 177 } 178 179 int table_size_old = _table_size; 180 // hash_to_index() uses _table_size, so switch the sizes now 181 _table_size = new_size; 182 183 // Move entries from the old table to a new table 184 for (int index_old = 0; index_old < table_size_old; index_old++) { 185 for (BasicHashtableEntry<F>* p = _buckets[index_old].get_entry(); p != NULL; ) { 186 BasicHashtableEntry<F>* next = p->next(); 187 bool keep_shared = p->is_shared(); 188 int index_new = hash_to_index(p->hash()); 189 190 p->set_next(buckets_new[index_new].get_entry()); 191 buckets_new[index_new].set_entry(p); 192 193 if (keep_shared) { 194 p->set_shared(); 195 } 196 p = next; 197 } 198 } 199 200 // The old backets now can be released 201 BasicHashtable<F>::free_buckets(); 202 203 // Switch to the new storage 204 _buckets = buckets_new; 205 206 return true; 207 } 208 209 template <MEMFLAGS F> bool BasicHashtable<F>::maybe_grow(int max_size, int load_factor) { 210 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 211 212 if (table_size() >= max_size) { 213 return false; 214 } 215 if (number_of_entries() / table_size() > load_factor) { 216 resize(MIN2<int>(table_size() * 2, max_size)); 217 return true; 218 } else { 219 return false; 220 } 221 } 222 223 // Dump footprint and bucket length statistics 224 // 225 // Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to 226 // add a new function static int literal_size(MyNewType lit) 227 // because I can't get template <class T> int literal_size(T) to pick the specializations for Symbol and oop. 228 // 229 // The StringTable and SymbolTable dumping print how much footprint is used by the String and Symbol 230 // literals. 231 232 template <class T, MEMFLAGS F> void Hashtable<T, F>::print_table_statistics(outputStream* st, 233 const char *table_name, 234 T (*literal_load_barrier)(HashtableEntry<T, F>*)) { 235 NumberSeq summary; 236 int literal_bytes = 0; 237 for (int i = 0; i < this->table_size(); ++i) { 238 int count = 0; 239 for (HashtableEntry<T, F>* e = this->bucket(i); 240 e != NULL; e = e->next()) { 241 count++; 242 T l = (literal_load_barrier != NULL) ? literal_load_barrier(e) : e->literal(); 243 literal_bytes += literal_size(l); 244 } 245 summary.add((double)count); 246 } 247 double num_buckets = summary.num(); 248 double num_entries = summary.sum(); 249 250 int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>); 251 int entry_bytes = (int)num_entries * sizeof(HashtableEntry<T, F>); 252 int total_bytes = literal_bytes + bucket_bytes + entry_bytes; 253 254 int bucket_size = (num_buckets <= 0) ? 0 : (bucket_bytes / num_buckets); 255 int entry_size = (num_entries <= 0) ? 0 : (entry_bytes / num_entries); 256 257 st->print_cr("%s statistics:", table_name); 258 st->print_cr("Number of buckets : %9d = %9d bytes, each %d", (int)num_buckets, bucket_bytes, bucket_size); 259 st->print_cr("Number of entries : %9d = %9d bytes, each %d", (int)num_entries, entry_bytes, entry_size); 260 if (literal_bytes != 0) { 261 double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries); 262 st->print_cr("Number of literals : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg); 263 } 264 st->print_cr("Total footprint : %9s = %9d bytes", "", total_bytes); 265 st->print_cr("Average bucket size : %9.3f", summary.avg()); 266 st->print_cr("Variance of bucket size : %9.3f", summary.variance()); 267 st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd()); 268 st->print_cr("Maximum bucket size : %9d", (int)summary.maximum()); 269 } 270 271 #ifndef PRODUCT 272 template <class T> void print_literal(T l) { 273 l->print(); 274 } 275 276 static void print_literal(ClassLoaderWeakHandle l) { 277 l.print(); 278 } 279 280 template <class T, MEMFLAGS F> void Hashtable<T, F>::print() { 281 ResourceMark rm; 282 283 for (int i = 0; i < BasicHashtable<F>::table_size(); i++) { 284 HashtableEntry<T, F>* entry = bucket(i); 285 while(entry != NULL) { 286 tty->print("%d : ", i); 287 print_literal(entry->literal()); 288 tty->cr(); 289 entry = entry->next(); 290 } 291 } 292 } 293 294 template <MEMFLAGS F> 295 template <class T> void BasicHashtable<F>::verify_table(const char* table_name) { 296 int element_count = 0; 297 int max_bucket_count = 0; 298 int max_bucket_number = 0; 299 for (int index = 0; index < table_size(); index++) { 300 int bucket_count = 0; 301 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) { 302 probe->verify(); 303 bucket_count++; 304 } 305 element_count += bucket_count; 306 if (bucket_count > max_bucket_count) { 307 max_bucket_count = bucket_count; 308 max_bucket_number = index; 309 } 310 } 311 guarantee(number_of_entries() == element_count, 312 "Verify of %s failed", table_name); 313 314 // Log some statistics about the hashtable 315 log_info(hashtables)("%s max bucket size %d bucket %d element count %d table size %d", table_name, 316 max_bucket_count, max_bucket_number, _number_of_entries, _table_size); 317 if (_number_of_entries > 0 && log_is_enabled(Debug, hashtables)) { 318 for (int index = 0; index < table_size(); index++) { 319 int bucket_count = 0; 320 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) { 321 log_debug(hashtables)("bucket %d hash " INTPTR_FORMAT, index, (intptr_t)probe->hash()); 322 bucket_count++; 323 } 324 if (bucket_count > 0) { 325 log_debug(hashtables)("bucket %d count %d", index, bucket_count); 326 } 327 } 328 } 329 } 330 #endif // PRODUCT 331 332 // Explicitly instantiate these types 333 template class Hashtable<nmethod*, mtGC>; 334 template class HashtableEntry<nmethod*, mtGC>; 335 template class BasicHashtable<mtGC>; 336 template class Hashtable<ConstantPool*, mtClass>; 337 template class Hashtable<Symbol*, mtSymbol>; 338 template class Hashtable<Klass*, mtClass>; 339 template class Hashtable<InstanceKlass*, mtClass>; 340 template class Hashtable<ClassLoaderWeakHandle, mtClass>; 341 template class Hashtable<Symbol*, mtModule>; 342 template class Hashtable<oop, mtSymbol>; 343 template class Hashtable<ClassLoaderWeakHandle, mtSymbol>; 344 template class Hashtable<Symbol*, mtClass>; 345 template class HashtableEntry<Symbol*, mtSymbol>; 346 template class HashtableEntry<Symbol*, mtClass>; 347 template class HashtableEntry<oop, mtSymbol>; 348 template class HashtableEntry<ClassLoaderWeakHandle, mtSymbol>; 349 template class HashtableBucket<mtClass>; 350 template class BasicHashtableEntry<mtSymbol>; 351 template class BasicHashtableEntry<mtCode>; 352 template class BasicHashtable<mtClass>; 353 template class BasicHashtable<mtClassShared>; 354 template class BasicHashtable<mtSymbol>; 355 template class BasicHashtable<mtCode>; 356 template class BasicHashtable<mtInternal>; 357 template class BasicHashtable<mtModule>; 358 template class BasicHashtable<mtCompiler>; 359 360 template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*); 361 template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*); 362 template void BasicHashtable<mtModule>::verify_table<PackageEntry>(char const*); 363 template void BasicHashtable<mtClass>::verify_table<ProtectionDomainCacheEntry>(char const*); 364 template void BasicHashtable<mtClass>::verify_table<PlaceholderEntry>(char const*);