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 /*

  * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

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  */

 #include "precompiled.hpp"

 #include "classfile/altHashing.hpp"

 #include "classfile/javaClasses.hpp"

 #include "memory/allocation.inline.hpp"

 #include "memory/filemap.hpp"

 #include "memory/resourceArea.hpp"

 #include "oops/oop.inline.hpp"

 #include "runtime/safepoint.hpp"

 #include "utilities/dtrace.hpp"

 #include "utilities/hashtable.hpp"

 #include "utilities/hashtable.inline.hpp"

 #include "utilities/numberSeq.hpp"

 // This is a generic hashtable, designed to be used for the symbol

 // and string tables.

 //

 // It is implemented as an open hash table with a fixed number of buckets.

 //

 // %note:

 //  - HashtableEntrys are allocated in blocks to reduce the space overhead.

 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) {

   BasicHashtableEntry<F>* entry;

   if (_free_list) {

     entry = _free_list;

     _free_list = _free_list->next();

   } else {

     if (_first_free_entry + _entry_size >= _end_block) {

       int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries));

       int len = _entry_size * block_size;

       len = 1 << log2_intptr(len); // round down to power of 2

       assert(len >= _entry_size, "");

       _first_free_entry = NEW_C_HEAP_ARRAY2(char, len, F, CURRENT_PC);

       _end_block = _first_free_entry + len;

     }

     entry = (BasicHashtableEntry<F>*)_first_free_entry;

     _first_free_entry += _entry_size;

   }

   assert(_entry_size % HeapWordSize == 0, "");

   entry->set_hash(hashValue);

   return entry;

 }

 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::new_entry(unsigned int hashValue, T obj) {

   HashtableEntry<T, F>* entry;

   entry = (HashtableEntry<T, F>*)BasicHashtable<F>::new_entry(hashValue);

   entry->set_literal(obj);

   return entry;

 }

 // Check to see if the hashtable is unbalanced.  The caller set a flag to

 // rehash at the next safepoint.  If this bucket is 60 times greater than the

 // expected average bucket length, it's an unbalanced hashtable.

 // This is somewhat an arbitrary heuristic but if one bucket gets to

 // rehash_count which is currently 100, there's probably something wrong.

 template <MEMFLAGS F> bool BasicHashtable<F>::check_rehash_table(int count) {

   assert(table_size() != 0, "underflow");

   if (count > (((double)number_of_entries()/(double)table_size())*rehash_multiple)) {

     // Set a flag for the next safepoint, which should be at some guaranteed

     // safepoint interval.

     return true;

   }

   return false;

 }

 template <class T, MEMFLAGS F> jint Hashtable<T, F>::_seed = 0;

 // Create a new table and using alternate hash code, populate the new table

 // with the existing elements.   This can be used to change the hash code

 // and could in the future change the size of the table.

 template <class T, MEMFLAGS F> void Hashtable<T, F>::move_to(Hashtable<T, F>* new_table) {

   // Initialize the global seed for hashing.

   _seed = AltHashing::compute_seed();

   assert(seed() != 0, "shouldn't be zero");

   int saved_entry_count = this->number_of_entries();

   // Iterate through the table and create a new entry for the new table

   for (int i = 0; i < new_table->table_size(); ++i) {

     for (HashtableEntry<T, F>* p = bucket(i); p != NULL; ) {

       HashtableEntry<T, F>* next = p->next();

       T string = p->literal();

       // Use alternate hashing algorithm on the symbol in the first table

       unsigned int hashValue = string->new_hash(seed());

       // Get a new index relative to the new table (can also change size)

       int index = new_table->hash_to_index(hashValue);

       p->set_hash(hashValue);

       // Keep the shared bit in the Hashtable entry to indicate that this entry

       // can't be deleted.   The shared bit is the LSB in the _next field so

       // walking the hashtable past these entries requires

       // BasicHashtableEntry::make_ptr() call.

       bool keep_shared = p->is_shared();

       this->unlink_entry(p);

       new_table->add_entry(index, p);

       if (keep_shared) {

         p->set_shared();

       }

       p = next;

     }

   }

   // give the new table the free list as well

   new_table->copy_freelist(this);

   assert(new_table->number_of_entries() == saved_entry_count, "lost entry on dictionary copy?");

   // Destroy memory used by the buckets in the hashtable.  The memory

   // for the elements has been used in a new table and is not

   // destroyed.  The memory reuse will benefit resizing the SystemDictionary

   // to avoid a memory allocation spike at safepoint.

   BasicHashtable<F>::free_buckets();

 }

 template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() {

   if (NULL != _buckets) {

     // Don't delete the buckets in the shared space.  They aren't

     // allocated by os::malloc

     if (!UseSharedSpaces ||

         !FileMapInfo::current_info()->is_in_shared_space(_buckets)) {

        FREE_C_HEAP_ARRAY(HashtableBucket, _buckets, F);

     }

     _buckets = NULL;

   }

 }

 // Reverse the order of elements in the hash buckets.

 template <MEMFLAGS F> void BasicHashtable<F>::reverse() {

   for (int i = 0; i < _table_size; ++i) {

     BasicHashtableEntry<F>* new_list = NULL;

     BasicHashtableEntry<F>* p = bucket(i);

     while (p != NULL) {

       BasicHashtableEntry<F>* next = p->next();

       p->set_next(new_list);

       new_list = p;

       p = next;

     }

     *bucket_addr(i) = new_list;

   }

 }

 // Copy the table to the shared space.

 template <MEMFLAGS F> void BasicHashtable<F>::copy_table(char** top, char* end) {

   // Dump the hash table entries.

   intptr_t *plen = (intptr_t*)(*top);

   *top += sizeof(*plen);

   int i;

   for (i = 0; i < _table_size; ++i) {

     for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr();

                               *p != NULL;

                                p = (*p)->next_addr()) {

       if (*top + entry_size() > end) {

         report_out_of_shared_space(SharedMiscData);

       }

       *p = (BasicHashtableEntry<F>*)memcpy(*top, *p, entry_size());

       *top += entry_size();

     }

   }

   *plen = (char*)(*top) - (char*)plen - sizeof(*plen);

   // Set the shared bit.

   for (i = 0; i < _table_size; ++i) {

     for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {

       p->set_shared();

     }

   }

 }

 // Reverse the order of elements in the hash buckets.

 template <class T, MEMFLAGS F> void Hashtable<T, F>::reverse(void* boundary) {

   for (int i = 0; i < this->table_size(); ++i) {

     HashtableEntry<T, F>* high_list = NULL;

     HashtableEntry<T, F>* low_list = NULL;

     HashtableEntry<T, F>* last_low_entry = NULL;

     HashtableEntry<T, F>* p = bucket(i);

     while (p != NULL) {

       HashtableEntry<T, F>* next = p->next();

       if ((void*)p->literal() >= boundary) {

         p->set_next(high_list);

         high_list = p;

       } else {

         p->set_next(low_list);

         low_list = p;

         if (last_low_entry == NULL) {

           last_low_entry = p;

         }

       }

       p = next;

     }

     if (low_list != NULL) {

       *bucket_addr(i) = low_list;

       last_low_entry->set_next(high_list);

     } else {

       *bucket_addr(i) = high_list;

     }

   }

 }

 template <class T, MEMFLAGS F> int Hashtable<T, F>::literal_size(Symbol *symbol) {

   return symbol->size() * HeapWordSize;

 }

 template <class T, MEMFLAGS F> int Hashtable<T, F>::literal_size(oop oop) {

   // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true,

   // and the String.value array is shared by several Strings. However, starting from JDK8,

   // the String.value array is not shared anymore.

   assert(oop != NULL && oop->klass() == SystemDictionary::String_klass(), "only strings are supported");

   return (oop->size() + java_lang_String::value(oop)->size()) * HeapWordSize;

 }

 // Dump footprint and bucket length statistics

 //

 // Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to

 // add a new function Hashtable<T, F>::literal_size(MyNewType lit)

 template <class T, MEMFLAGS F> void Hashtable<T, F>::dump_table(outputStream* st, const char *table_name) {

   NumberSeq summary;

   int literal_bytes = 0;

   for (int i = 0; i < this->table_size(); ++i) {

     int count = 0;

     for (HashtableEntry<T, F>* e = bucket(i);

        e != NULL; e = e->next()) {

       count++;

       literal_bytes += literal_size(e->literal());

     }

     summary.add((double)count);

   }

   double num_buckets = summary.num();

   double num_entries = summary.sum();

   int bucket_bytes = (int)num_buckets * sizeof(bucket(0));

   int entry_bytes  = (int)num_entries * sizeof(HashtableEntry<T, F>);

   int total_bytes = literal_bytes +  bucket_bytes + entry_bytes;

   double bucket_avg  = (num_buckets <= 0) ? 0 : (bucket_bytes  / num_buckets);

   double entry_avg   = (num_entries <= 0) ? 0 : (entry_bytes   / num_entries);

   double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries);

   st->print_cr("%s statistics:", table_name);

   st->print_cr("Number of buckets       : %9d = %9d bytes, avg %7.3f", (int)num_buckets, bucket_bytes,  bucket_avg);

   st->print_cr("Number of entries       : %9d = %9d bytes, avg %7.3f", (int)num_entries, entry_bytes,   entry_avg);

   st->print_cr("Number of literals      : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg);

   st->print_cr("Total footprint         : %9s = %9d bytes", "", total_bytes);

   st->print_cr("Average bucket size     : %9.3f", summary.avg());

   st->print_cr("Variance of bucket size : %9.3f", summary.variance());

   st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd());

   st->print_cr("Maximum bucket size     : %9d", (int)summary.maximum());

 }

 // Dump the hash table buckets.

 template <MEMFLAGS F> void BasicHashtable<F>::copy_buckets(char** top, char* end) {

   intptr_t len = _table_size * sizeof(HashtableBucket<F>);

   *(intptr_t*)(*top) = len;

   *top += sizeof(intptr_t);

   *(intptr_t*)(*top) = _number_of_entries;

   *top += sizeof(intptr_t);

   if (*top + len > end) {

     report_out_of_shared_space(SharedMiscData);

   }

   _buckets = (HashtableBucket<F>*)memcpy(*top, _buckets, len);

   *top += len;

 }

 #ifndef PRODUCT

 template <class T, MEMFLAGS F> void Hashtable<T, F>::print() {

   ResourceMark rm;

   for (int i = 0; i < BasicHashtable<F>::table_size(); i++) {

     HashtableEntry<T, F>* entry = bucket(i);

     while(entry != NULL) {

       tty->print("%d : ", i);

       entry->literal()->print();

       tty->cr();

       entry = entry->next();

     }

   }

 }

 template <MEMFLAGS F> void BasicHashtable<F>::verify() {

   int count = 0;

   for (int i = 0; i < table_size(); i++) {

     for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {

       ++count;

     }

   }

   assert(count == number_of_entries(), "number of hashtable entries incorrect");

 }

 #endif // PRODUCT

 #ifdef ASSERT

 template <MEMFLAGS F> void BasicHashtable<F>::verify_lookup_length(double load) {

   if ((double)_lookup_length / (double)_lookup_count > load * 2.0) {

     warning("Performance bug: SystemDictionary lookup_count=%d "

             "lookup_length=%d average=%lf load=%f",

             _lookup_count, _lookup_length,

             (double) _lookup_length / _lookup_count, load);

   }

 }

 #endif

 // Explicitly instantiate these types

 template class Hashtable<ConstantPool*, mtClass>;

 template class Hashtable<Symbol*, mtSymbol>;

 template class Hashtable<Klass*, mtClass>;

 template class Hashtable<oop, mtClass>;

 #ifdef SOLARIS

 template class Hashtable<oop, mtSymbol>;

 #endif

 template class Hashtable<oopDesc*, mtSymbol>;

 template class Hashtable<Symbol*, mtClass>;

 template class HashtableEntry<Symbol*, mtSymbol>;

 template class HashtableEntry<Symbol*, mtClass>;

 template class HashtableEntry<oop, mtSymbol>;

 template class BasicHashtableEntry<mtSymbol>;

 template class BasicHashtableEntry<mtCode>;

 template class BasicHashtable<mtClass>;

 template class BasicHashtable<mtSymbol>;

 template class BasicHashtable<mtCode>;

 template class BasicHashtable<mtInternal>;