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 template <class T, MEMFLAGS F> juint RehashableHashtable<T, F>::_seed = 0;
 104 
 105 // Create a new table and using alternate hash code, populate the new table
 106 // with the existing elements.   This can be used to change the hash code
 107 // and could in the future change the size of the table.
 108 
 109 template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::move_to(RehashableHashtable<T, F>* new_table) {
 110 
 111   // Initialize the global seed for hashing.
 112   _seed = AltHashing::compute_seed();
 113   assert(seed() != 0, "shouldn't be zero");
 114 
 115   int saved_entry_count = this->number_of_entries();
 116 
 117   // Iterate through the table and create a new entry for the new table
 118   for (int i = 0; i < new_table->table_size(); ++i) {
 119     for (HashtableEntry<T, F>* p = this->bucket(i); p != NULL; ) {
 120       HashtableEntry<T, F>* next = p->next();
 121       T string = p->literal();
 122       // Use alternate hashing algorithm on the symbol in the first table
 123       unsigned int hashValue = string->new_hash(seed());
 124       // Get a new index relative to the new table (can also change size)
 125       int index = new_table->hash_to_index(hashValue);
 126       p->set_hash(hashValue);
 127       // Keep the shared bit in the Hashtable entry to indicate that this entry
 128       // can't be deleted.   The shared bit is the LSB in the _next field so
 129       // walking the hashtable past these entries requires
 130       // BasicHashtableEntry::make_ptr() call.
 131       bool keep_shared = p->is_shared();
 132       this->unlink_entry(p);
 133       new_table->add_entry(index, p);
 134       if (keep_shared) {
 135         p->set_shared();
 136       }
 137       p = next;
 138     }
 139   }
 140   // give the new table the free list as well
 141   new_table->copy_freelist(this);
 142   assert(new_table->number_of_entries() == saved_entry_count, "lost entry on dictionary copy?");
 143 
 144   // Destroy memory used by the buckets in the hashtable.  The memory
 145   // for the elements has been used in a new table and is not
 146   // destroyed.  The memory reuse will benefit resizing the SystemDictionary
 147   // to avoid a memory allocation spike at safepoint.
 148   BasicHashtable<F>::free_buckets();
 149 }
 150 
 151 template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() {
 152   if (NULL != _buckets) {
 153     // Don't delete the buckets in the shared space.  They aren't
 154     // allocated by os::malloc
 155     if (!UseSharedSpaces ||
 156         !FileMapInfo::current_info()->is_in_shared_space(_buckets)) {
 157        FREE_C_HEAP_ARRAY(HashtableBucket, _buckets);
 158     }
 159     _buckets = NULL;
 160   }
 161 }
 162 
 163 template <MEMFLAGS F> void BasicHashtable<F>::BucketUnlinkContext::free_entry(BasicHashtableEntry<F>* entry) {
 164   entry->set_next(_removed_head);
 165   _removed_head = entry;
 166   if (_removed_tail == NULL) {
 167     _removed_tail = entry;
 168   }
 169   _num_removed++;
 170 }
 171 
 172 template <MEMFLAGS F> void BasicHashtable<F>::bulk_free_entries(BucketUnlinkContext* context) {
 173   if (context->_num_removed == 0) {
 174     assert(context->_removed_head == NULL && context->_removed_tail == NULL,
 175            "Zero entries in the unlink context, but elements linked from " PTR_FORMAT " to " PTR_FORMAT,
 176            p2i(context->_removed_head), p2i(context->_removed_tail));
 177     return;
 178   }
 179 
 180   // MT-safe add of the list of BasicHashTableEntrys from the context to the free list.
 181   BasicHashtableEntry<F>* current = _free_list;
 182   while (true) {
 183     context->_removed_tail->set_next(current);
 184     BasicHashtableEntry<F>* old = (BasicHashtableEntry<F>*)Atomic::cmpxchg_ptr(context->_removed_head, &_free_list, current);
 185     if (old == current) {
 186       break;
 187     }
 188     current = old;
 189   }
 190   Atomic::add(-context->_num_removed, &_number_of_entries);
 191 }
 192 
 193 // Copy the table to the shared space.
 194 
 195 template <MEMFLAGS F> void BasicHashtable<F>::copy_table(char** top, char* end) {
 196 
 197   // Dump the hash table entries.
 198 
 199   intptr_t *plen = (intptr_t*)(*top);
 200   *top += sizeof(*plen);
 201 
 202   int i;
 203   for (i = 0; i < _table_size; ++i) {
 204     for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr();
 205                               *p != NULL;
 206                                p = (*p)->next_addr()) {
 207       if (*top + entry_size() > end) {
 208         report_out_of_shared_space(SharedMiscData);
 209       }
 210       *p = (BasicHashtableEntry<F>*)memcpy(*top, *p, entry_size());
 211       *top += entry_size();
 212     }
 213   }
 214   *plen = (char*)(*top) - (char*)plen - sizeof(*plen);
 215 
 216   // Set the shared bit.
 217 
 218   for (i = 0; i < _table_size; ++i) {
 219     for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {
 220       p->set_shared();
 221     }
 222   }
 223 }
 224 
 225 template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(Symbol *symbol) {
 226   return symbol->size() * HeapWordSize;
 227 }
 228 
 229 template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(oop oop) {
 230   // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true,
 231   // and the String.value array is shared by several Strings. However, starting from JDK8,
 232   // the String.value array is not shared anymore.
 233   assert(oop != NULL && oop->klass() == SystemDictionary::String_klass(), "only strings are supported");
 234   return (oop->size() + java_lang_String::value(oop)->size()) * HeapWordSize;
 235 }
 236 
 237 // Dump footprint and bucket length statistics
 238 //
 239 // Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to
 240 // add a new function Hashtable<T, F>::literal_size(MyNewType lit)
 241 
 242 template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::dump_table(outputStream* st, const char *table_name) {
 243   NumberSeq summary;
 244   int literal_bytes = 0;
 245   for (int i = 0; i < this->table_size(); ++i) {
 246     int count = 0;
 247     for (HashtableEntry<T, F>* e = this->bucket(i);
 248        e != NULL; e = e->next()) {
 249       count++;
 250       literal_bytes += literal_size(e->literal());
 251     }
 252     summary.add((double)count);
 253   }
 254   double num_buckets = summary.num();
 255   double num_entries = summary.sum();
 256 
 257   int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>);
 258   int entry_bytes  = (int)num_entries * sizeof(HashtableEntry<T, F>);
 259   int total_bytes = literal_bytes +  bucket_bytes + entry_bytes;
 260 
 261   double bucket_avg  = (num_buckets <= 0) ? 0 : (bucket_bytes  / num_buckets);
 262   double entry_avg   = (num_entries <= 0) ? 0 : (entry_bytes   / num_entries);
 263   double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries);
 264 
 265   st->print_cr("%s statistics:", table_name);
 266   st->print_cr("Number of buckets       : %9d = %9d bytes, avg %7.3f", (int)num_buckets, bucket_bytes,  bucket_avg);
 267   st->print_cr("Number of entries       : %9d = %9d bytes, avg %7.3f", (int)num_entries, entry_bytes,   entry_avg);
 268   st->print_cr("Number of literals      : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg);
 269   st->print_cr("Total footprint         : %9s = %9d bytes", "", total_bytes);
 270   st->print_cr("Average bucket size     : %9.3f", summary.avg());
 271   st->print_cr("Variance of bucket size : %9.3f", summary.variance());
 272   st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd());
 273   st->print_cr("Maximum bucket size     : %9d", (int)summary.maximum());
 274 }
 275 
 276 
 277 // Dump the hash table buckets.
 278 
 279 template <MEMFLAGS F> void BasicHashtable<F>::copy_buckets(char** top, char* end) {
 280   intptr_t len = _table_size * sizeof(HashtableBucket<F>);
 281   *(intptr_t*)(*top) = len;
 282   *top += sizeof(intptr_t);
 283 
 284   *(intptr_t*)(*top) = _number_of_entries;
 285   *top += sizeof(intptr_t);
 286 
 287   if (*top + len > end) {
 288     report_out_of_shared_space(SharedMiscData);
 289   }
 290   _buckets = (HashtableBucket<F>*)memcpy(*top, _buckets, len);
 291   *top += len;
 292 }
 293 
 294 
 295 #ifndef PRODUCT
 296 
 297 template <class T, MEMFLAGS F> void Hashtable<T, F>::print() {
 298   ResourceMark rm;
 299 
 300   for (int i = 0; i < BasicHashtable<F>::table_size(); i++) {
 301     HashtableEntry<T, F>* entry = bucket(i);
 302     while(entry != NULL) {
 303       tty->print("%d : ", i);
 304       entry->literal()->print();
 305       tty->cr();
 306       entry = entry->next();
 307     }
 308   }
 309 }
 310 
 311 template <MEMFLAGS F>
 312 template <class T> void BasicHashtable<F>::verify_table(const char* table_name) {
 313   int element_count = 0;
 314   int max_bucket_count = 0;
 315   int max_bucket_number = 0;
 316   for (int index = 0; index < table_size(); index++) {
 317     int bucket_count = 0;
 318     for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
 319       probe->verify();
 320       bucket_count++;
 321     }
 322     element_count += bucket_count;
 323     if (bucket_count > max_bucket_count) {
 324       max_bucket_count = bucket_count;
 325       max_bucket_number = index;
 326     }
 327   }
 328   guarantee(number_of_entries() == element_count,
 329             "Verify of %s failed", table_name);
 330 
 331   // Log some statistics about the hashtable
 332   log_info(hashtables)("%s max bucket size %d bucket %d element count %d table size %d", table_name,
 333                        max_bucket_count, max_bucket_number, _number_of_entries, _table_size);
 334   if (_number_of_entries > 0 && log_is_enabled(Debug, hashtables)) {
 335     for (int index = 0; index < table_size(); index++) {
 336       int bucket_count = 0;
 337       for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
 338         log_debug(hashtables)("bucket %d hash " INTPTR_FORMAT, index, (intptr_t)probe->hash());
 339         bucket_count++;
 340       }
 341       if (bucket_count > 0) {
 342         log_debug(hashtables)("bucket %d count %d", index, bucket_count);
 343       }
 344     }
 345   }
 346 }
 347 #endif // PRODUCT
 348 
 349 // Explicitly instantiate these types
 350 #if INCLUDE_ALL_GCS
 351 template class Hashtable<nmethod*, mtGC>;
 352 template class HashtableEntry<nmethod*, mtGC>;
 353 template class BasicHashtable<mtGC>;
 354 #endif
 355 template class Hashtable<ConstantPool*, mtClass>;
 356 template class RehashableHashtable<Symbol*, mtSymbol>;
 357 template class RehashableHashtable<oopDesc*, mtSymbol>;
 358 template class Hashtable<Symbol*, mtSymbol>;
 359 template class Hashtable<Klass*, mtClass>;
 360 template class Hashtable<InstanceKlass*, mtClass>;
 361 template class Hashtable<oop, mtClass>;
 362 #if defined(SOLARIS) || defined(CHECK_UNHANDLED_OOPS)
 363 template class Hashtable<oop, mtSymbol>;
 364 template class RehashableHashtable<oop, mtSymbol>;
 365 #endif // SOLARIS || CHECK_UNHANDLED_OOPS
 366 template class Hashtable<oopDesc*, mtSymbol>;
 367 template class Hashtable<Symbol*, mtClass>;
 368 template class HashtableEntry<Symbol*, mtSymbol>;
 369 template class HashtableEntry<Symbol*, mtClass>;
 370 template class HashtableEntry<oop, mtSymbol>;
 371 template class BasicHashtableEntry<mtSymbol>;
 372 template class BasicHashtableEntry<mtCode>;
 373 template class BasicHashtable<mtClass>;
 374 template class BasicHashtable<mtClassShared>;
 375 template class BasicHashtable<mtSymbol>;
 376 template class BasicHashtable<mtCode>;
 377 template class BasicHashtable<mtInternal>;
 378 template class BasicHashtable<mtModule>;
 379 #if INCLUDE_TRACE
 380 template class Hashtable<Symbol*, mtTracing>;
 381 template class HashtableEntry<Symbol*, mtTracing>;
 382 template class BasicHashtable<mtTracing>;
 383 #endif
 384 template class BasicHashtable<mtCompiler>;
 385 
 386 template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*);
 387 template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*);
 388 template void BasicHashtable<mtModule>::verify_table<PackageEntry>(char const*);
 389 template void BasicHashtable<mtClass>::verify_table<ProtectionDomainCacheEntry>(char const*);
 390 template void BasicHashtable<mtClass>::verify_table<PlaceholderEntry>(char const*);
 391