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 #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 "memory/allocation.inline.hpp" 35 #include "memory/filemap.hpp" 36 #include "memory/resourceArea.hpp" 37 #include "oops/oop.inline.hpp" 38 #include "runtime/safepoint.hpp" 39 #include "utilities/dtrace.hpp" 40 #include "utilities/hashtable.hpp" 41 #include "utilities/hashtable.inline.hpp" 42 #include "utilities/numberSeq.hpp" 43 44 45 // This hashtable is implemented as an open hash table with a fixed number of buckets. 46 47 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry_free_list() { 48 BasicHashtableEntry<F>* entry = NULL; 49 if (_free_list != NULL) { 50 entry = _free_list; 51 _free_list = _free_list->next(); 52 } 53 return entry; 54 } 55 56 // HashtableEntrys are allocated in blocks to reduce the space overhead. 57 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) { 58 BasicHashtableEntry<F>* entry = new_entry_free_list(); 59 60 if (entry == NULL) { 61 if (_first_free_entry + _entry_size >= _end_block) { 62 int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries)); 63 int len = _entry_size * block_size; 64 len = 1 << log2_intptr(len); // round down to power of 2 65 assert(len >= _entry_size, ""); 66 _first_free_entry = NEW_C_HEAP_ARRAY2(char, len, F, CURRENT_PC); 67 _end_block = _first_free_entry + len; 68 } 69 entry = (BasicHashtableEntry<F>*)_first_free_entry; 70 _first_free_entry += _entry_size; 71 } 72 73 assert(_entry_size % HeapWordSize == 0, ""); 74 entry->set_hash(hashValue); 75 return entry; 76 } 77 78 79 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::new_entry(unsigned int hashValue, T obj) { 80 HashtableEntry<T, F>* entry; 81 82 entry = (HashtableEntry<T, F>*)BasicHashtable<F>::new_entry(hashValue); 83 entry->set_literal(obj); 84 return entry; 85 } 86 87 // Check to see if the hashtable is unbalanced. The caller set a flag to 88 // rehash at the next safepoint. If this bucket is 60 times greater than the 89 // expected average bucket length, it's an unbalanced hashtable. 90 // This is somewhat an arbitrary heuristic but if one bucket gets to 91 // rehash_count which is currently 100, there's probably something wrong. 92 93 template <class T, MEMFLAGS F> bool RehashableHashtable<T, F>::check_rehash_table(int count) { 94 assert(this->table_size() != 0, "underflow"); 95 if (count > (((double)this->number_of_entries()/(double)this->table_size())*rehash_multiple)) { 96 // Set a flag for the next safepoint, which should be at some guaranteed 97 // safepoint interval. 98 return true; 99 } 100 return false; 101 } 102 103 // Create a new table and using alternate hash code, populate the new table 104 // with the existing elements. This can be used to change the hash code 105 // and could in the future change the size of the table. 106 107 template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::move_to(RehashableHashtable<T, F>* new_table) { 108 109 // Initialize the global seed for hashing. 110 _seed = AltHashing::compute_seed(); 111 assert(seed() != 0, "shouldn't be zero"); 112 113 int saved_entry_count = this->number_of_entries(); 114 115 // Iterate through the table and create a new entry for the new table 116 for (int i = 0; i < new_table->table_size(); ++i) { 117 for (HashtableEntry<T, F>* p = this->bucket(i); p != NULL; ) { 118 HashtableEntry<T, F>* next = p->next(); 119 T string = p->literal(); 120 // Use alternate hashing algorithm on the symbol in the first table 121 unsigned int hashValue = string->new_hash(seed()); 122 // Get a new index relative to the new table (can also change size) 123 int index = new_table->hash_to_index(hashValue); 124 p->set_hash(hashValue); 125 // Keep the shared bit in the Hashtable entry to indicate that this entry 126 // can't be deleted. The shared bit is the LSB in the _next field so 127 // walking the hashtable past these entries requires 128 // BasicHashtableEntry::make_ptr() call. 129 bool keep_shared = p->is_shared(); 130 this->unlink_entry(p); 131 new_table->add_entry(index, p); 132 if (keep_shared) { 133 p->set_shared(); 134 } 135 p = next; 136 } 137 } 138 // give the new table the free list as well 139 new_table->copy_freelist(this); 140 assert(new_table->number_of_entries() == saved_entry_count, "lost entry on dictionary copy?"); 141 142 // Destroy memory used by the buckets in the hashtable. The memory 143 // for the elements has been used in a new table and is not 144 // destroyed. The memory reuse will benefit resizing the SystemDictionary 145 // to avoid a memory allocation spike at safepoint. 146 BasicHashtable<F>::free_buckets(); 147 } 148 149 template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() { 150 if (NULL != _buckets) { 151 // Don't delete the buckets in the shared space. They aren't 152 // allocated by os::malloc 153 if (!UseSharedSpaces || 154 !FileMapInfo::current_info()->is_in_shared_space(_buckets)) { 155 FREE_C_HEAP_ARRAY(HashtableBucket, _buckets); 156 } 157 _buckets = NULL; 158 } 159 } 160 161 template <MEMFLAGS F> void BasicHashtable<F>::BucketUnlinkContext::free_entry(BasicHashtableEntry<F>* entry) { 162 entry->set_next(_removed_head); 163 _removed_head = entry; 164 if (_removed_tail == NULL) { 165 _removed_tail = entry; 166 } 167 _num_removed++; 168 } 169 170 template <MEMFLAGS F> void BasicHashtable<F>::bulk_free_entries(BucketUnlinkContext* context) { 171 if (context->_num_removed == 0) { 172 assert(context->_removed_head == NULL && context->_removed_tail == NULL, 173 "Zero entries in the unlink context, but elements linked from " PTR_FORMAT " to " PTR_FORMAT, 174 p2i(context->_removed_head), p2i(context->_removed_tail)); 175 return; 176 } 177 178 // MT-safe add of the list of BasicHashTableEntrys from the context to the free list. 179 BasicHashtableEntry<F>* current = _free_list; 180 while (true) { 181 context->_removed_tail->set_next(current); 182 BasicHashtableEntry<F>* old = (BasicHashtableEntry<F>*)Atomic::cmpxchg_ptr(context->_removed_head, &_free_list, current); 183 if (old == current) { 184 break; 185 } 186 current = old; 187 } 188 Atomic::add(-context->_num_removed, &_number_of_entries); 189 } 190 191 // Copy the table to the shared space. 192 193 template <MEMFLAGS F> void BasicHashtable<F>::copy_table(char** top, char* end) { 194 195 // Dump the hash table entries. 196 197 intptr_t *plen = (intptr_t*)(*top); 198 *top += sizeof(*plen); 199 200 int i; 201 for (i = 0; i < _table_size; ++i) { 202 for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr(); 203 *p != NULL; 204 p = (*p)->next_addr()) { 205 if (*top + entry_size() > end) { 206 report_out_of_shared_space(SharedMiscData); 207 } 208 *p = (BasicHashtableEntry<F>*)memcpy(*top, *p, entry_size()); 209 *top += entry_size(); 210 } 211 } 212 *plen = (char*)(*top) - (char*)plen - sizeof(*plen); 213 214 // Set the shared bit. 215 216 for (i = 0; i < _table_size; ++i) { 217 for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) { 218 p->set_shared(); 219 } 220 } 221 } 222 223 template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(Symbol *symbol) { 224 return symbol->size() * HeapWordSize; 225 } 226 227 template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(oop oop) { 228 // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true, 229 // and the String.value array is shared by several Strings. However, starting from JDK8, 230 // the String.value array is not shared anymore. 231 assert(oop != NULL && oop->klass() == SystemDictionary::String_klass(), "only strings are supported"); 232 return (oop->size() + java_lang_String::value(oop)->size()) * HeapWordSize; 233 } 234 235 // Dump footprint and bucket length statistics 236 // 237 // Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to 238 // add a new function Hashtable<T, F>::literal_size(MyNewType lit) 239 240 template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::dump_table(outputStream* st, const char *table_name) { 241 NumberSeq summary; 242 int literal_bytes = 0; 243 for (int i = 0; i < this->table_size(); ++i) { 244 int count = 0; 245 for (HashtableEntry<T, F>* e = this->bucket(i); 246 e != NULL; e = e->next()) { 247 count++; 248 literal_bytes += literal_size(e->literal()); 249 } 250 summary.add((double)count); 251 } 252 double num_buckets = summary.num(); 253 double num_entries = summary.sum(); 254 255 int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>); 256 int entry_bytes = (int)num_entries * sizeof(HashtableEntry<T, F>); 257 int total_bytes = literal_bytes + bucket_bytes + entry_bytes; 258 259 double bucket_avg = (num_buckets <= 0) ? 0 : (bucket_bytes / num_buckets); 260 double entry_avg = (num_entries <= 0) ? 0 : (entry_bytes / num_entries); 261 double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries); 262 263 st->print_cr("%s statistics:", table_name); 264 st->print_cr("Number of buckets : %9d = %9d bytes, avg %7.3f", (int)num_buckets, bucket_bytes, bucket_avg); 265 st->print_cr("Number of entries : %9d = %9d bytes, avg %7.3f", (int)num_entries, entry_bytes, entry_avg); 266 st->print_cr("Number of literals : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg); 267 st->print_cr("Total footprint : %9s = %9d bytes", "", total_bytes); 268 st->print_cr("Average bucket size : %9.3f", summary.avg()); 269 st->print_cr("Variance of bucket size : %9.3f", summary.variance()); 270 st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd()); 271 st->print_cr("Maximum bucket size : %9d", (int)summary.maximum()); 272 } 273 274 275 // Dump the hash table buckets. 276 277 template <MEMFLAGS F> void BasicHashtable<F>::copy_buckets(char** top, char* end) { 278 intptr_t len = _table_size * sizeof(HashtableBucket<F>); 279 *(intptr_t*)(*top) = len; 280 *top += sizeof(intptr_t); 281 282 *(intptr_t*)(*top) = _number_of_entries; 283 *top += sizeof(intptr_t); 284 285 if (*top + len > end) { 286 report_out_of_shared_space(SharedMiscData); 287 } 288 _buckets = (HashtableBucket<F>*)memcpy(*top, _buckets, len); 289 *top += len; 290 } 291 292 293 #ifndef PRODUCT 294 295 template <class T, MEMFLAGS F> void Hashtable<T, F>::print() { 296 ResourceMark rm; 297 298 for (int i = 0; i < BasicHashtable<F>::table_size(); i++) { 299 HashtableEntry<T, F>* entry = bucket(i); 300 while(entry != NULL) { 301 tty->print("%d : ", i); 302 entry->literal()->print(); 303 tty->cr(); 304 entry = entry->next(); 305 } 306 } 307 } 308 309 template <MEMFLAGS F> 310 template <class T> void BasicHashtable<F>::verify_table(const char* table_name) { 311 int element_count = 0; 312 int max_bucket_count = 0; 313 int max_bucket_number = 0; 314 for (int index = 0; index < table_size(); index++) { 315 int bucket_count = 0; 316 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) { 317 probe->verify(); 318 bucket_count++; 319 } 320 element_count += bucket_count; 321 if (bucket_count > max_bucket_count) { 322 max_bucket_count = bucket_count; 323 max_bucket_number = index; 324 } 325 } 326 guarantee(number_of_entries() == element_count, 327 "Verify of %s failed", table_name); 328 329 // Log some statistics about the hashtable 330 log_info(hashtables)("%s max bucket size %d bucket %d element count %d table size %d", table_name, 331 max_bucket_count, max_bucket_number, _number_of_entries, _table_size); 332 if (_number_of_entries > 0 && log_is_enabled(Debug, hashtables)) { 333 for (int index = 0; index < table_size(); index++) { 334 int bucket_count = 0; 335 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) { 336 log_debug(hashtables)("bucket %d hash " INTPTR_FORMAT, index, (intptr_t)probe->hash()); 337 bucket_count++; 338 } 339 if (bucket_count > 0) { 340 log_debug(hashtables)("bucket %d count %d", index, bucket_count); 341 } 342 } 343 } 344 } 345 #endif // PRODUCT 346 347 // Explicitly instantiate these types 348 #if INCLUDE_ALL_GCS 349 template class Hashtable<nmethod*, mtGC>; 350 template class HashtableEntry<nmethod*, mtGC>; 351 template class BasicHashtable<mtGC>; 352 #endif 353 template class Hashtable<ConstantPool*, mtClass>; 354 template class RehashableHashtable<Symbol*, mtSymbol>; 355 template class RehashableHashtable<oopDesc*, mtSymbol>; 356 template class Hashtable<Symbol*, mtSymbol>; 357 template class Hashtable<Klass*, mtClass>; 358 template class Hashtable<InstanceKlass*, mtClass>; 359 template class Hashtable<oop, mtClass>; 360 #if defined(SOLARIS) || defined(CHECK_UNHANDLED_OOPS) 361 template class Hashtable<oop, mtSymbol>; 362 template class RehashableHashtable<oop, mtSymbol>; 363 #endif // SOLARIS || CHECK_UNHANDLED_OOPS 364 template class Hashtable<oopDesc*, mtSymbol>; 365 template class Hashtable<Symbol*, mtClass>; 366 template class HashtableEntry<Symbol*, mtSymbol>; 367 template class HashtableEntry<Symbol*, mtClass>; 368 template class HashtableEntry<oop, mtSymbol>; 369 template class BasicHashtableEntry<mtSymbol>; 370 template class BasicHashtableEntry<mtCode>; 371 template class BasicHashtable<mtClass>; 372 template class BasicHashtable<mtClassShared>; 373 template class BasicHashtable<mtSymbol>; 374 template class BasicHashtable<mtCode>; 375 template class BasicHashtable<mtInternal>; 376 template class BasicHashtable<mtModule>; 377 #if INCLUDE_TRACE 378 template class Hashtable<Symbol*, mtTracing>; 379 template class HashtableEntry<Symbol*, mtTracing>; 380 template class BasicHashtable<mtTracing>; 381 #endif 382 template class BasicHashtable<mtCompiler>; 383 384 template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*); 385 template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*); 386 template void BasicHashtable<mtModule>::verify_table<PackageEntry>(char const*); 387 template void BasicHashtable<mtClass>::verify_table<ProtectionDomainCacheEntry>(char const*); 388 template void BasicHashtable<mtClass>::verify_table<PlaceholderEntry>(char const*); 389