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_intptr(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 // Dump footprint and bucket length statistics
 210 //
 211 // Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to
 212 // add a new function static int literal_size(MyNewType lit)
 213 // because I can't get template <class T> int literal_size(T) to pick the specializations for Symbol and oop.
 214 //
 215 // The StringTable and SymbolTable dumping print how much footprint is used by the String and Symbol
 216 // literals.
 217 
 218 template <class T, MEMFLAGS F> void Hashtable<T, F>::print_table_statistics(outputStream* st,
 219                                                                             const char *table_name,
 220                                                                             T (*literal_load_barrier)(HashtableEntry<T, F>*)) {
 221   NumberSeq summary;
 222   int literal_bytes = 0;
 223   for (int i = 0; i < this->table_size(); ++i) {
 224     int count = 0;
 225     for (HashtableEntry<T, F>* e = this->bucket(i);
 226          e != NULL; e = e->next()) {
 227       count++;
 228       T l = (literal_load_barrier != NULL) ? literal_load_barrier(e) : e->literal();
 229       literal_bytes += literal_size(l);
 230     }
 231     summary.add((double)count);
 232   }
 233   double num_buckets = summary.num();
 234   double num_entries = summary.sum();
 235 
 236   int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>);
 237   int entry_bytes  = (int)num_entries * sizeof(HashtableEntry<T, F>);
 238   int total_bytes = literal_bytes +  bucket_bytes + entry_bytes;
 239 
 240   int bucket_size  = (num_buckets <= 0) ? 0 : (bucket_bytes  / num_buckets);
 241   int entry_size   = (num_entries <= 0) ? 0 : (entry_bytes   / num_entries);
 242 
 243   st->print_cr("%s statistics:", table_name);
 244   st->print_cr("Number of buckets       : %9d = %9d bytes, each %d", (int)num_buckets, bucket_bytes,  bucket_size);
 245   st->print_cr("Number of entries       : %9d = %9d bytes, each %d", (int)num_entries, entry_bytes,   entry_size);
 246   if (literal_bytes != 0) {
 247     double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries);
 248     st->print_cr("Number of literals      : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg);
 249   }
 250   st->print_cr("Total footprint         : %9s = %9d bytes", "", total_bytes);
 251   st->print_cr("Average bucket size     : %9.3f", summary.avg());
 252   st->print_cr("Variance of bucket size : %9.3f", summary.variance());
 253   st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd());
 254   st->print_cr("Maximum bucket size     : %9d", (int)summary.maximum());
 255 }
 256 
 257 #ifndef PRODUCT
 258 template <class T> void print_literal(T l) {
 259   l->print();
 260 }
 261 
 262 static void print_literal(ClassLoaderWeakHandle l) {
 263   l.print();
 264 }
 265 
 266 template <class T, MEMFLAGS F> void Hashtable<T, F>::print() {
 267   ResourceMark rm;
 268 
 269   for (int i = 0; i < BasicHashtable<F>::table_size(); i++) {
 270     HashtableEntry<T, F>* entry = bucket(i);
 271     while(entry != NULL) {
 272       tty->print("%d : ", i);
 273       print_literal(entry->literal());
 274       tty->cr();
 275       entry = entry->next();
 276     }
 277   }
 278 }
 279 
 280 template <MEMFLAGS F>
 281 template <class T> void BasicHashtable<F>::verify_table(const char* table_name) {
 282   int element_count = 0;
 283   int max_bucket_count = 0;
 284   int max_bucket_number = 0;
 285   for (int index = 0; index < table_size(); index++) {
 286     int bucket_count = 0;
 287     for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
 288       probe->verify();
 289       bucket_count++;
 290     }
 291     element_count += bucket_count;
 292     if (bucket_count > max_bucket_count) {
 293       max_bucket_count = bucket_count;
 294       max_bucket_number = index;
 295     }
 296   }
 297   guarantee(number_of_entries() == element_count,
 298             "Verify of %s failed", table_name);
 299 
 300   // Log some statistics about the hashtable
 301   log_info(hashtables)("%s max bucket size %d bucket %d element count %d table size %d", table_name,
 302                        max_bucket_count, max_bucket_number, _number_of_entries, _table_size);
 303   if (_number_of_entries > 0 && log_is_enabled(Debug, hashtables)) {
 304     for (int index = 0; index < table_size(); index++) {
 305       int bucket_count = 0;
 306       for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
 307         log_debug(hashtables)("bucket %d hash " INTPTR_FORMAT, index, (intptr_t)probe->hash());
 308         bucket_count++;
 309       }
 310       if (bucket_count > 0) {
 311         log_debug(hashtables)("bucket %d count %d", index, bucket_count);
 312       }
 313     }
 314   }
 315 }
 316 #endif // PRODUCT
 317 
 318 // Explicitly instantiate these types
 319 template class Hashtable<nmethod*, mtGC>;
 320 template class HashtableEntry<nmethod*, mtGC>;
 321 template class BasicHashtable<mtGC>;
 322 template class Hashtable<ConstantPool*, mtClass>;
 323 template class Hashtable<Symbol*, mtSymbol>;
 324 template class Hashtable<Klass*, mtClass>;
 325 template class Hashtable<InstanceKlass*, mtClass>;
 326 template class Hashtable<ClassLoaderWeakHandle, mtClass>;
 327 template class Hashtable<Symbol*, mtModule>;
 328 template class Hashtable<oop, mtSymbol>;
 329 template class Hashtable<ClassLoaderWeakHandle, mtSymbol>;
 330 template class Hashtable<Symbol*, mtClass>;
 331 template class HashtableEntry<Symbol*, mtSymbol>;
 332 template class HashtableEntry<Symbol*, mtClass>;
 333 template class HashtableEntry<oop, mtSymbol>;
 334 template class HashtableEntry<ClassLoaderWeakHandle, mtSymbol>;
 335 template class HashtableBucket<mtClass>;
 336 template class BasicHashtableEntry<mtSymbol>;
 337 template class BasicHashtableEntry<mtCode>;
 338 template class BasicHashtable<mtClass>;
 339 template class BasicHashtable<mtClassShared>;
 340 template class BasicHashtable<mtSymbol>;
 341 template class BasicHashtable<mtCode>;
 342 template class BasicHashtable<mtInternal>;
 343 template class BasicHashtable<mtModule>;
 344 template class BasicHashtable<mtCompiler>;
 345 
 346 template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*);
 347 template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*);
 348 template void BasicHashtable<mtModule>::verify_table<PackageEntry>(char const*);
 349 template void BasicHashtable<mtClass>::verify_table<ProtectionDomainCacheEntry>(char const*);
 350 template void BasicHashtable<mtClass>::verify_table<PlaceholderEntry>(char const*);