hashtable.cpp revision 13370:731370f39fcd
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 47template <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. 57template <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 79template <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// Version of hashtable entry allocation that allocates in the C heap directly. 88// The allocator in blocks is preferable but doesn't have free semantics. 89template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::allocate_new_entry(unsigned int hashValue, T obj) { 90 HashtableEntry<T, F>* entry = (HashtableEntry<T, F>*) NEW_C_HEAP_ARRAY(char, this->entry_size(), F); 91 92 entry->set_hash(hashValue); 93 entry->set_literal(obj); 94 entry->set_next(NULL); 95 return entry; 96} 97 98// Check to see if the hashtable is unbalanced. The caller set a flag to 99// rehash at the next safepoint. If this bucket is 60 times greater than the 100// expected average bucket length, it's an unbalanced hashtable. 101// This is somewhat an arbitrary heuristic but if one bucket gets to 102// rehash_count which is currently 100, there's probably something wrong. 103 104template <class T, MEMFLAGS F> bool RehashableHashtable<T, F>::check_rehash_table(int count) { 105 assert(this->table_size() != 0, "underflow"); 106 if (count > (((double)this->number_of_entries()/(double)this->table_size())*rehash_multiple)) { 107 // Set a flag for the next safepoint, which should be at some guaranteed 108 // safepoint interval. 109 return true; 110 } 111 return false; 112} 113 114// Create a new table and using alternate hash code, populate the new table 115// with the existing elements. This can be used to change the hash code 116// and could in the future change the size of the table. 117 118template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::move_to(RehashableHashtable<T, F>* new_table) { 119 120 // Initialize the global seed for hashing. 121 _seed = AltHashing::compute_seed(); 122 assert(seed() != 0, "shouldn't be zero"); 123 124 int saved_entry_count = this->number_of_entries(); 125 126 // Iterate through the table and create a new entry for the new table 127 for (int i = 0; i < new_table->table_size(); ++i) { 128 for (HashtableEntry<T, F>* p = this->bucket(i); p != NULL; ) { 129 HashtableEntry<T, F>* next = p->next(); 130 T string = p->literal(); 131 // Use alternate hashing algorithm on the symbol in the first table 132 unsigned int hashValue = string->new_hash(seed()); 133 // Get a new index relative to the new table (can also change size) 134 int index = new_table->hash_to_index(hashValue); 135 p->set_hash(hashValue); 136 // Keep the shared bit in the Hashtable entry to indicate that this entry 137 // can't be deleted. The shared bit is the LSB in the _next field so 138 // walking the hashtable past these entries requires 139 // BasicHashtableEntry::make_ptr() call. 140 bool keep_shared = p->is_shared(); 141 this->unlink_entry(p); 142 new_table->add_entry(index, p); 143 if (keep_shared) { 144 p->set_shared(); 145 } 146 p = next; 147 } 148 } 149 // give the new table the free list as well 150 new_table->copy_freelist(this); 151 assert(new_table->number_of_entries() == saved_entry_count, "lost entry on dictionary copy?"); 152 153 // Destroy memory used by the buckets in the hashtable. The memory 154 // for the elements has been used in a new table and is not 155 // destroyed. The memory reuse will benefit resizing the SystemDictionary 156 // to avoid a memory allocation spike at safepoint. 157 BasicHashtable<F>::free_buckets(); 158} 159 160template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() { 161 if (NULL != _buckets) { 162 // Don't delete the buckets in the shared space. They aren't 163 // allocated by os::malloc 164 if (!UseSharedSpaces || 165 !FileMapInfo::current_info()->is_in_shared_space(_buckets)) { 166 FREE_C_HEAP_ARRAY(HashtableBucket, _buckets); 167 } 168 _buckets = NULL; 169 } 170} 171 172template <MEMFLAGS F> void BasicHashtable<F>::BucketUnlinkContext::free_entry(BasicHashtableEntry<F>* entry) { 173 entry->set_next(_removed_head); 174 _removed_head = entry; 175 if (_removed_tail == NULL) { 176 _removed_tail = entry; 177 } 178 _num_removed++; 179} 180 181template <MEMFLAGS F> void BasicHashtable<F>::bulk_free_entries(BucketUnlinkContext* context) { 182 if (context->_num_removed == 0) { 183 assert(context->_removed_head == NULL && context->_removed_tail == NULL, 184 "Zero entries in the unlink context, but elements linked from " PTR_FORMAT " to " PTR_FORMAT, 185 p2i(context->_removed_head), p2i(context->_removed_tail)); 186 return; 187 } 188 189 // MT-safe add of the list of BasicHashTableEntrys from the context to the free list. 190 BasicHashtableEntry<F>* current = _free_list; 191 while (true) { 192 context->_removed_tail->set_next(current); 193 BasicHashtableEntry<F>* old = (BasicHashtableEntry<F>*)Atomic::cmpxchg_ptr(context->_removed_head, &_free_list, current); 194 if (old == current) { 195 break; 196 } 197 current = old; 198 } 199 Atomic::add(-context->_num_removed, &_number_of_entries); 200} 201// Copy the table to the shared space. 202template <MEMFLAGS F> size_t BasicHashtable<F>::count_bytes_for_table() { 203 size_t bytes = 0; 204 bytes += sizeof(intptr_t); // len 205 206 for (int i = 0; i < _table_size; ++i) { 207 for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr(); 208 *p != NULL; 209 p = (*p)->next_addr()) { 210 bytes += entry_size(); 211 } 212 } 213 214 return bytes; 215} 216 217// Dump the hash table entries (into CDS archive) 218template <MEMFLAGS F> void BasicHashtable<F>::copy_table(char* top, char* end) { 219 assert(is_aligned(top, sizeof(intptr_t)), "bad alignment"); 220 intptr_t *plen = (intptr_t*)(top); 221 top += sizeof(*plen); 222 223 int i; 224 for (i = 0; i < _table_size; ++i) { 225 for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr(); 226 *p != NULL; 227 p = (*p)->next_addr()) { 228 *p = (BasicHashtableEntry<F>*)memcpy(top, (void*)*p, entry_size()); 229 top += entry_size(); 230 } 231 } 232 *plen = (char*)(top) - (char*)plen - sizeof(*plen); 233 assert(top == end, "count_bytes_for_table is wrong"); 234 // Set the shared bit. 235 236 for (i = 0; i < _table_size; ++i) { 237 for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) { 238 p->set_shared(); 239 } 240 } 241} 242 243// For oops and Strings the size of the literal is interesting. For other types, nobody cares. 244static int literal_size(ConstantPool*) { return 0; } 245static int literal_size(Klass*) { return 0; } 246#if INCLUDE_ALL_GCS 247static int literal_size(nmethod*) { return 0; } 248#endif 249 250static int literal_size(Symbol *symbol) { 251 return symbol->size() * HeapWordSize; 252} 253 254static int literal_size(oop obj) { 255 // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true, 256 // and the String.value array is shared by several Strings. However, starting from JDK8, 257 // the String.value array is not shared anymore. 258 if (obj == NULL) { 259 return 0; 260 } else if (obj->klass() == SystemDictionary::String_klass()) { 261 return (obj->size() + java_lang_String::value(obj)->size()) * HeapWordSize; 262 } else { 263 return obj->size(); 264 } 265} 266 267 268// Dump footprint and bucket length statistics 269// 270// Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to 271// add a new function static int literal_size(MyNewType lit) 272// because I can't get template <class T> int literal_size(T) to pick the specializations for Symbol and oop. 273// 274// The StringTable and SymbolTable dumping print how much footprint is used by the String and Symbol 275// literals. 276 277template <class T, MEMFLAGS F> void Hashtable<T, F>::print_table_statistics(outputStream* st, 278 const char *table_name) { 279 NumberSeq summary; 280 int literal_bytes = 0; 281 for (int i = 0; i < this->table_size(); ++i) { 282 int count = 0; 283 for (HashtableEntry<T, F>* e = this->bucket(i); 284 e != NULL; e = e->next()) { 285 count++; 286 literal_bytes += literal_size(e->literal()); 287 } 288 summary.add((double)count); 289 } 290 double num_buckets = summary.num(); 291 double num_entries = summary.sum(); 292 293 int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>); 294 int entry_bytes = (int)num_entries * sizeof(HashtableEntry<T, F>); 295 int total_bytes = literal_bytes + bucket_bytes + entry_bytes; 296 297 int bucket_size = (num_buckets <= 0) ? 0 : (bucket_bytes / num_buckets); 298 int entry_size = (num_entries <= 0) ? 0 : (entry_bytes / num_entries); 299 300 st->print_cr("%s statistics:", table_name); 301 st->print_cr("Number of buckets : %9d = %9d bytes, each %d", (int)num_buckets, bucket_bytes, bucket_size); 302 st->print_cr("Number of entries : %9d = %9d bytes, each %d", (int)num_entries, entry_bytes, entry_size); 303 if (literal_bytes != 0) { 304 double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries); 305 st->print_cr("Number of literals : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg); 306 } 307 st->print_cr("Total footprint : %9s = %9d bytes", "", total_bytes); 308 st->print_cr("Average bucket size : %9.3f", summary.avg()); 309 st->print_cr("Variance of bucket size : %9.3f", summary.variance()); 310 st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd()); 311 st->print_cr("Maximum bucket size : %9d", (int)summary.maximum()); 312} 313 314 315// Dump the hash table buckets. 316 317template <MEMFLAGS F> size_t BasicHashtable<F>::count_bytes_for_buckets() { 318 size_t bytes = 0; 319 bytes += sizeof(intptr_t); // len 320 bytes += sizeof(intptr_t); // _number_of_entries 321 bytes += _table_size * sizeof(HashtableBucket<F>); // the buckets 322 323 return bytes; 324} 325 326// Dump the buckets (into CDS archive) 327template <MEMFLAGS F> void BasicHashtable<F>::copy_buckets(char* top, char* end) { 328 assert(is_aligned(top, sizeof(intptr_t)), "bad alignment"); 329 intptr_t len = _table_size * sizeof(HashtableBucket<F>); 330 *(intptr_t*)(top) = len; 331 top += sizeof(intptr_t); 332 333 *(intptr_t*)(top) = _number_of_entries; 334 top += sizeof(intptr_t); 335 336 _buckets = (HashtableBucket<F>*)memcpy(top, (void*)_buckets, len); 337 top += len; 338 339 assert(top == end, "count_bytes_for_buckets is wrong"); 340} 341 342#ifndef PRODUCT 343 344template <class T, MEMFLAGS F> void Hashtable<T, F>::print() { 345 ResourceMark rm; 346 347 for (int i = 0; i < BasicHashtable<F>::table_size(); i++) { 348 HashtableEntry<T, F>* entry = bucket(i); 349 while(entry != NULL) { 350 tty->print("%d : ", i); 351 entry->literal()->print(); 352 tty->cr(); 353 entry = entry->next(); 354 } 355 } 356} 357 358template <MEMFLAGS F> 359template <class T> void BasicHashtable<F>::verify_table(const char* table_name) { 360 int element_count = 0; 361 int max_bucket_count = 0; 362 int max_bucket_number = 0; 363 for (int index = 0; index < table_size(); index++) { 364 int bucket_count = 0; 365 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) { 366 probe->verify(); 367 bucket_count++; 368 } 369 element_count += bucket_count; 370 if (bucket_count > max_bucket_count) { 371 max_bucket_count = bucket_count; 372 max_bucket_number = index; 373 } 374 } 375 guarantee(number_of_entries() == element_count, 376 "Verify of %s failed", table_name); 377 378 // Log some statistics about the hashtable 379 log_info(hashtables)("%s max bucket size %d bucket %d element count %d table size %d", table_name, 380 max_bucket_count, max_bucket_number, _number_of_entries, _table_size); 381 if (_number_of_entries > 0 && log_is_enabled(Debug, hashtables)) { 382 for (int index = 0; index < table_size(); index++) { 383 int bucket_count = 0; 384 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) { 385 log_debug(hashtables)("bucket %d hash " INTPTR_FORMAT, index, (intptr_t)probe->hash()); 386 bucket_count++; 387 } 388 if (bucket_count > 0) { 389 log_debug(hashtables)("bucket %d count %d", index, bucket_count); 390 } 391 } 392 } 393} 394#endif // PRODUCT 395 396// Explicitly instantiate these types 397#if INCLUDE_ALL_GCS 398template class Hashtable<nmethod*, mtGC>; 399template class HashtableEntry<nmethod*, mtGC>; 400template class BasicHashtable<mtGC>; 401#endif 402template class Hashtable<ConstantPool*, mtClass>; 403template class RehashableHashtable<Symbol*, mtSymbol>; 404template class RehashableHashtable<oopDesc*, mtSymbol>; 405template class Hashtable<Symbol*, mtSymbol>; 406template class Hashtable<Klass*, mtClass>; 407template class Hashtable<InstanceKlass*, mtClass>; 408template class Hashtable<oop, mtClass>; 409template class Hashtable<Symbol*, mtModule>; 410#if defined(SOLARIS) || defined(CHECK_UNHANDLED_OOPS) 411template class Hashtable<oop, mtSymbol>; 412template class RehashableHashtable<oop, mtSymbol>; 413#endif // SOLARIS || CHECK_UNHANDLED_OOPS 414template class Hashtable<oopDesc*, mtSymbol>; 415template class Hashtable<Symbol*, mtClass>; 416template class HashtableEntry<Symbol*, mtSymbol>; 417template class HashtableEntry<Symbol*, mtClass>; 418template class HashtableEntry<oop, mtSymbol>; 419template class HashtableBucket<mtClass>; 420template class BasicHashtableEntry<mtSymbol>; 421template class BasicHashtableEntry<mtCode>; 422template class BasicHashtable<mtClass>; 423template class BasicHashtable<mtClassShared>; 424template class BasicHashtable<mtSymbol>; 425template class BasicHashtable<mtCode>; 426template class BasicHashtable<mtInternal>; 427template class BasicHashtable<mtModule>; 428#if INCLUDE_TRACE 429template class Hashtable<Symbol*, mtTracing>; 430template class HashtableEntry<Symbol*, mtTracing>; 431template class BasicHashtable<mtTracing>; 432#endif 433template class BasicHashtable<mtCompiler>; 434 435template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*); 436template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*); 437template void BasicHashtable<mtModule>::verify_table<PackageEntry>(char const*); 438template void BasicHashtable<mtClass>::verify_table<ProtectionDomainCacheEntry>(char const*); 439template void BasicHashtable<mtClass>::verify_table<PlaceholderEntry>(char const*); 440