       1 /*
       2  * Copyright (c) 2003, 2014, 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/javaClasses.hpp"
      28 #include "memory/allocation.inline.hpp"
      29 #include "memory/filemap.hpp"
      30 #include "memory/resourceArea.hpp"
      31 #include "oops/oop.inline.hpp"
      32 #include "runtime/safepoint.hpp"
      33 #include "utilities/dtrace.hpp"
      34 #include "utilities/hashtable.hpp"
      35 #include "utilities/hashtable.inline.hpp"
      36 #include "utilities/numberSeq.hpp"
      37

      38
      39 // This hashtable is implemented as an open hash table with a fixed number of buckets.
      40
      41 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry_free_list() {
      42   BasicHashtableEntry<F>* entry = NULL;
      43   if (_free_list != NULL) {
      44     entry = _free_list;
      45     _free_list = _free_list->next();
      46   }
      47   return entry;
      48 }
      49
      50 // HashtableEntrys are allocated in blocks to reduce the space overhead.
      51 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) {
      52   BasicHashtableEntry<F>* entry = new_entry_free_list();
      53
      54   if (entry == NULL) {
      55     if (_first_free_entry + _entry_size >= _end_block) {
      56       int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries));
      57       int len = _entry_size * block_size;
      58       len = 1 << log2_intptr(len); // round down to power of 2
      59       assert(len >= _entry_size, "");
      60       _first_free_entry = NEW_C_HEAP_ARRAY2(char, len, F, CURRENT_PC);
      61       _end_block = _first_free_entry + len;
      62     }
      63     entry = (BasicHashtableEntry<F>*)_first_free_entry;
      64     _first_free_entry += _entry_size;
      65   }
      66
      67   assert(_entry_size % HeapWordSize == 0, "");
      68   entry->set_hash(hashValue);
      69   return entry;
      70 }
      71
      72
      73 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::new_entry(unsigned int hashValue, T obj) {
      74   HashtableEntry<T, F>* entry;
      75
      76   entry = (HashtableEntry<T, F>*)BasicHashtable<F>::new_entry(hashValue);
      77   entry->set_literal(obj);

      78   return entry;
      79 }
      80
      81 // Check to see if the hashtable is unbalanced.  The caller set a flag to
      82 // rehash at the next safepoint.  If this bucket is 60 times greater than the
      83 // expected average bucket length, it's an unbalanced hashtable.
      84 // This is somewhat an arbitrary heuristic but if one bucket gets to
      85 // rehash_count which is currently 100, there's probably something wrong.
      86
      87 template <class T, MEMFLAGS F> bool RehashableHashtable<T, F>::check_rehash_table(int count) {
      88   assert(this->table_size() != 0, "underflow");
      89   if (count > (((double)this->number_of_entries()/(double)this->table_size())*rehash_multiple)) {
      90     // Set a flag for the next safepoint, which should be at some guaranteed
      91     // safepoint interval.
      92     return true;
      93   }
      94   return false;
      95 }
      96
      97 template <class T, MEMFLAGS F> juint RehashableHashtable<T, F>::_seed = 0;
      98
      99 // Create a new table and using alternate hash code, populate the new table
     100 // with the existing elements.   This can be used to change the hash code
     101 // and could in the future change the size of the table.
     102
     103 template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::move_to(RehashableHashtable<T, F>* new_table) {
     104
     105   // Initialize the global seed for hashing.
     106   _seed = AltHashing::compute_seed();
     107   assert(seed() != 0, "shouldn't be zero");
     108
     109   int saved_entry_count = this->number_of_entries();
     110
     111   // Iterate through the table and create a new entry for the new table
     112   for (int i = 0; i < new_table->table_size(); ++i) {
     113     for (HashtableEntry<T, F>* p = this->bucket(i); p != NULL; ) {
     114       HashtableEntry<T, F>* next = p->next();
     115       T string = p->literal();
     116       // Use alternate hashing algorithm on the symbol in the first table
     117       unsigned int hashValue = string->new_hash(seed());
     118       // Get a new index relative to the new table (can also change size)
     119       int index = new_table->hash_to_index(hashValue);
     120       p->set_hash(hashValue);
     121       // Keep the shared bit in the Hashtable entry to indicate that this entry
     122       // can't be deleted.   The shared bit is the LSB in the _next field so
     123       // walking the hashtable past these entries requires
     124       // BasicHashtableEntry::make_ptr() call.
     125       bool keep_shared = p->is_shared();
     126       this->unlink_entry(p);
     127       new_table->add_entry(index, p);
     128       if (keep_shared) {
     129         p->set_shared();
     130       }
     131       p = next;
     132     }
     133   }
     134   // give the new table the free list as well
     135   new_table->copy_freelist(this);
     136   assert(new_table->number_of_entries() == saved_entry_count, "lost entry on dictionary copy?");
     137
     138   // Destroy memory used by the buckets in the hashtable.  The memory
     139   // for the elements has been used in a new table and is not
     140   // destroyed.  The memory reuse will benefit resizing the SystemDictionary
     141   // to avoid a memory allocation spike at safepoint.
     142   BasicHashtable<F>::free_buckets();
     143 }
     144
     145 template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() {
     146   if (NULL != _buckets) {
     147     // Don't delete the buckets in the shared space.  They aren't
     148     // allocated by os::malloc
     149     if (!UseSharedSpaces ||
     150         !FileMapInfo::current_info()->is_in_shared_space(_buckets)) {
     151        FREE_C_HEAP_ARRAY(HashtableBucket, _buckets, F);
     152     }
     153     _buckets = NULL;
     154   }
     155 }
     156

     157
     158 // Reverse the order of elements in the hash buckets.
     159
     160 template <MEMFLAGS F> void BasicHashtable<F>::reverse() {
     161
     162   for (int i = 0; i < _table_size; ++i) {
     163     BasicHashtableEntry<F>* new_list = NULL;
     164     BasicHashtableEntry<F>* p = bucket(i);
     165     while (p != NULL) {
     166       BasicHashtableEntry<F>* next = p->next();
     167       p->set_next(new_list);
     168       new_list = p;
     169       p = next;
     170     }
     171     *bucket_addr(i) = new_list;
     172   }
     173 }
     174
     175
     176 // Copy the table to the shared space.
     177
     178 template <MEMFLAGS F> void BasicHashtable<F>::copy_table(char** top, char* end) {
     179
     180   // Dump the hash table entries.
     181
     182   intptr_t *plen = (intptr_t*)(*top);
     183   *top += sizeof(*plen);
     184
     185   int i;
     186   for (i = 0; i < _table_size; ++i) {
     187     for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr();
     188                               *p != NULL;
     189                                p = (*p)->next_addr()) {
     190       if (*top + entry_size() > end) {
     191         report_out_of_shared_space(SharedMiscData);
     192       }
     193       *p = (BasicHashtableEntry<F>*)memcpy(*top, *p, entry_size());
     194       *top += entry_size();
     195     }
     196   }
     197   *plen = (char*)(*top) - (char*)plen - sizeof(*plen);
     198
     199   // Set the shared bit.
     200
     201   for (i = 0; i < _table_size; ++i) {
     202     for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {
     203       p->set_shared();
     204     }
     205   }
     206 }
     207
     208
     209
     210 // Reverse the order of elements in the hash buckets.
     211
     212 template <class T, MEMFLAGS F> void Hashtable<T, F>::reverse(void* boundary) {
     213
     214   for (int i = 0; i < this->table_size(); ++i) {
     215     HashtableEntry<T, F>* high_list = NULL;
     216     HashtableEntry<T, F>* low_list = NULL;
     217     HashtableEntry<T, F>* last_low_entry = NULL;
     218     HashtableEntry<T, F>* p = bucket(i);
     219     while (p != NULL) {
     220       HashtableEntry<T, F>* next = p->next();
     221       if ((void*)p->literal() >= boundary) {
     222         p->set_next(high_list);
     223         high_list = p;
     224       } else {
     225         p->set_next(low_list);
     226         low_list = p;
     227         if (last_low_entry == NULL) {
     228           last_low_entry = p;
     229         }
     230       }
     231       p = next;
     232     }
     233     if (low_list != NULL) {
     234       *bucket_addr(i) = low_list;
     235       last_low_entry->set_next(high_list);
     236     } else {
     237       *bucket_addr(i) = high_list;
     238     }
     239   }
     240 }
     241
     242 template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(Symbol *symbol) {

     243   return symbol->size() * HeapWordSize;
     244 }
     245
     246 template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(oop oop) {
     247   // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true,
     248   // and the String.value array is shared by several Strings. However, starting from JDK8,
     249   // the String.value array is not shared anymore.
     250   assert(oop != NULL && oop->klass() == SystemDictionary::String_klass(), "only strings are supported");
     251   return (oop->size() + java_lang_String::value(oop)->size()) * HeapWordSize;
     252 }
     253

     254 // Dump footprint and bucket length statistics
     255 //
     256 // Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to
     257 // add a new function Hashtable<T, F>::literal_size(MyNewType lit)
     258
     259 template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::dump_table(outputStream* st, const char *table_name) {
     260   NumberSeq summary;
     261   int literal_bytes = 0;
     262   for (int i = 0; i < this->table_size(); ++i) {
     263     int count = 0;
     264     for (HashtableEntry<T, F>* e = this->bucket(i);
     265        e != NULL; e = e->next()) {
     266       count++;
     267       literal_bytes += literal_size(e->literal());
     268     }
     269     summary.add((double)count);
     270   }
     271   double num_buckets = summary.num();
     272   double num_entries = summary.sum();
     273
     274   int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>);
     275   int entry_bytes  = (int)num_entries * sizeof(HashtableEntry<T, F>);
     276   int total_bytes = literal_bytes +  bucket_bytes + entry_bytes;
     277
     278   double bucket_avg  = (num_buckets <= 0) ? 0 : (bucket_bytes  / num_buckets);
     279   double entry_avg   = (num_entries <= 0) ? 0 : (entry_bytes   / num_entries);
     280   double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries);
     281
     282   st->print_cr("%s statistics:", table_name);
     283   st->print_cr("Number of buckets       : %9d = %9d bytes, avg %7.3f", (int)num_buckets, bucket_bytes,  bucket_avg);
     284   st->print_cr("Number of entries       : %9d = %9d bytes, avg %7.3f", (int)num_entries, entry_bytes,   entry_avg);
     285   st->print_cr("Number of literals      : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg);
     286   st->print_cr("Total footprint         : %9s = %9d bytes", "", total_bytes);
     287   st->print_cr("Average bucket size     : %9.3f", summary.avg());
     288   st->print_cr("Variance of bucket size : %9.3f", summary.variance());
     289   st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd());
     290   st->print_cr("Maximum bucket size     : %9d", (int)summary.maximum());
     291 }
     292
     293
     294 // Dump the hash table buckets.
     295
     296 template <MEMFLAGS F> void BasicHashtable<F>::copy_buckets(char** top, char* end) {
     297   intptr_t len = _table_size * sizeof(HashtableBucket<F>);
     298   *(intptr_t*)(*top) = len;
     299   *top += sizeof(intptr_t);
     300
     301   *(intptr_t*)(*top) = _number_of_entries;
     302   *top += sizeof(intptr_t);
     303
     304   if (*top + len > end) {
     305     report_out_of_shared_space(SharedMiscData);
     306   }
     307   _buckets = (HashtableBucket<F>*)memcpy(*top, _buckets, len);
     308   *top += len;

     309 }
     310
     311
     312 #ifndef PRODUCT
     313
     314 template <class T, MEMFLAGS F> void Hashtable<T, F>::print() {
     315   ResourceMark rm;
     316
     317   for (int i = 0; i < BasicHashtable<F>::table_size(); i++) {
     318     HashtableEntry<T, F>* entry = bucket(i);
     319     while(entry != NULL) {
     320       tty->print("%d : ", i);
     321       entry->literal()->print();
     322       tty->cr();
     323       entry = entry->next();
     324     }
     325   }
     326 }
     327
     328
     329 template <MEMFLAGS F> void BasicHashtable<F>::verify() {
     330   int count = 0;
     331   for (int i = 0; i < table_size(); i++) {
     332     for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {
     333       ++count;
     334     }
     335   }
     336   assert(count == number_of_entries(), "number of hashtable entries incorrect");
     337 }
     338
     339
     340 #endif // PRODUCT
     341
     342
     343 #ifdef ASSERT
     344
     345 template <MEMFLAGS F> void BasicHashtable<F>::verify_lookup_length(double load) {
     346   if ((double)_lookup_length / (double)_lookup_count > load * 2.0) {
     347     warning("Performance bug: SystemDictionary lookup_count=%d "
     348             "lookup_length=%d average=%lf load=%f",
     349             _lookup_count, _lookup_length,
     350             (double) _lookup_length / _lookup_count, load);
     351   }
     352 }
     353
     354 #endif

     355 // Explicitly instantiate these types
     356 #if INCLUDE_ALL_GCS
     357 template class Hashtable<nmethod*, mtGC>;
     358 template class HashtableEntry<nmethod*, mtGC>;
     359 template class BasicHashtable<mtGC>;
     360 #endif
     361 template class Hashtable<ConstantPool*, mtClass>;
     362 template class RehashableHashtable<Symbol*, mtSymbol>;
     363 template class RehashableHashtable<oopDesc*, mtSymbol>;
     364 template class Hashtable<Symbol*, mtSymbol>;
     365 template class Hashtable<Klass*, mtClass>;
     366 template class Hashtable<oop, mtClass>;
     367 #if defined(SOLARIS) || defined(CHECK_UNHANDLED_OOPS)
     368 template class Hashtable<oop, mtSymbol>;
     369 template class RehashableHashtable<oop, mtSymbol>;
     370 #endif // SOLARIS || CHECK_UNHANDLED_OOPS
     371 template class Hashtable<oopDesc*, mtSymbol>;
     372 template class Hashtable<Symbol*, mtClass>;
     373 template class HashtableEntry<Symbol*, mtSymbol>;
     374 template class HashtableEntry<Symbol*, mtClass>;
     375 template class HashtableEntry<oop, mtSymbol>;
     376 template class BasicHashtableEntry<mtSymbol>;
     377 template class BasicHashtableEntry<mtCode>;
     378 template class BasicHashtable<mtClass>;
     379 template class BasicHashtable<mtSymbol>;
     380 template class BasicHashtable<mtCode>;
     381 template class BasicHashtable<mtInternal>;
    --- EOF ---