jdk8-mips64-public/hotspot: src/share/vm/classfile/symbolTable.cpp@595c0f60d50d (annotated)

src/share/vm/classfile/symbolTable.cpp@595c0f60d50d (annotated)

src/share/vm/classfile/symbolTable.cpp

Tue, 18 Mar 2014 19:07:22 +0100

author: pliden
date: Tue, 18 Mar 2014 19:07:22 +0100
changeset 6413: 595c0f60d50d
parent 6229: 5a32d2a3cc1e
child 6680: 78bbf4d43a14
permissions: -rw-r--r--

8029075: String deduplication in G1
Summary: Implementation of JEP 192, http://openjdk.java.net/jeps/192
Reviewed-by: brutisso, tschatzl, coleenp

 /*
  * Copyright (c) 1997, 2014, 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
  * questions.
  *
  */
 #include "precompiled.hpp"
 #include "classfile/altHashing.hpp"
 #include "classfile/javaClasses.hpp"
 #include "classfile/symbolTable.hpp"
 #include "classfile/systemDictionary.hpp"
 #include "gc_interface/collectedHeap.inline.hpp"
 #include "memory/allocation.inline.hpp"
 #include "memory/filemap.hpp"
 #include "memory/gcLocker.inline.hpp"
 #include "oops/oop.inline.hpp"
 #include "oops/oop.inline2.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "utilities/hashtable.inline.hpp"
 #if INCLUDE_ALL_GCS
 #include "gc_implementation/g1/g1StringDedup.hpp"
 #endif
 // --------------------------------------------------------------------------
 // the number of buckets a thread claims
 const int ClaimChunkSize = 32;
 SymbolTable* SymbolTable::_the_table = NULL;
 // Static arena for symbols that are not deallocated
 Arena* SymbolTable::_arena = NULL;
 bool SymbolTable::_needs_rehashing = false;
 Symbol* SymbolTable::allocate_symbol(const u1* name, int len, bool c_heap, TRAPS) {
   assert (len <= Symbol::max_length(), "should be checked by caller");
   Symbol* sym;
   if (DumpSharedSpaces) {
     // Allocate all symbols to CLD shared metaspace
     sym = new (len, ClassLoaderData::the_null_class_loader_data(), THREAD) Symbol(name, len, -1);
   } else if (c_heap) {
     // refcount starts as 1
     sym = new (len, THREAD) Symbol(name, len, 1);
     assert(sym != NULL, "new should call vm_exit_out_of_memory if C_HEAP is exhausted");
   } else {
     // Allocate to global arena
     sym = new (len, arena(), THREAD) Symbol(name, len, -1);
   }
   return sym;
 }
 void SymbolTable::initialize_symbols(int arena_alloc_size) {
   // Initialize the arena for global symbols, size passed in depends on CDS.
   if (arena_alloc_size == 0) {
     _arena = new (mtSymbol) Arena();
   } else {
     _arena = new (mtSymbol) Arena(arena_alloc_size);
   }
 }
 // Call function for all symbols in the symbol table.
 void SymbolTable::symbols_do(SymbolClosure *cl) {
   const int n = the_table()->table_size();
   for (int i = 0; i < n; i++) {
     for (HashtableEntry<Symbol*, mtSymbol>* p = the_table()->bucket(i);
          p != NULL;
          p = p->next()) {
       cl->do_symbol(p->literal_addr());
     }
   }
 }
 int SymbolTable::_symbols_removed = 0;
 int SymbolTable::_symbols_counted = 0;
 volatile int SymbolTable::_parallel_claimed_idx = 0;
 void SymbolTable::buckets_unlink(int start_idx, int end_idx, int* processed, int* removed, size_t* memory_total) {
   for (int i = start_idx; i < end_idx; ++i) {
     HashtableEntry<Symbol*, mtSymbol>** p = the_table()->bucket_addr(i);
     HashtableEntry<Symbol*, mtSymbol>* entry = the_table()->bucket(i);
     while (entry != NULL) {
       // Shared entries are normally at the end of the bucket and if we run into
       // a shared entry, then there is nothing more to remove. However, if we
       // have rehashed the table, then the shared entries are no longer at the
       // end of the bucket.
       if (entry->is_shared() && !use_alternate_hashcode()) {
         break;
       }
       Symbol* s = entry->literal();
       (*memory_total) += s->size();
       (*processed)++;
       assert(s != NULL, "just checking");
       // If reference count is zero, remove.
       if (s->refcount() == 0) {
         assert(!entry->is_shared(), "shared entries should be kept live");
         delete s;
         (*removed)++;
         *p = entry->next();
         the_table()->free_entry(entry);
       } else {
         p = entry->next_addr();
       }
       // get next entry
       entry = (HashtableEntry<Symbol*, mtSymbol>*)HashtableEntry<Symbol*, mtSymbol>::make_ptr(*p);
     }
   }
 }
 // Remove unreferenced symbols from the symbol table
 // This is done late during GC.
 void SymbolTable::unlink(int* processed, int* removed) {
   size_t memory_total = 0;
   buckets_unlink(0, the_table()->table_size(), processed, removed, &memory_total);
   _symbols_removed += *removed;
   _symbols_counted += *processed;
   // Exclude printing for normal PrintGCDetails because people parse
   // this output.
   if (PrintGCDetails && Verbose && WizardMode) {
     gclog_or_tty->print(" [Symbols=%d size=" SIZE_FORMAT "K] ", *processed,
                         (memory_total*HeapWordSize)/1024);
   }
 }
 void SymbolTable::possibly_parallel_unlink(int* processed, int* removed) {
   const int limit = the_table()->table_size();
   size_t memory_total = 0;
   for (;;) {
     // Grab next set of buckets to scan
     int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
     if (start_idx >= limit) {
       // End of table
       break;
     }
     int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
     buckets_unlink(start_idx, end_idx, processed, removed, &memory_total);
   }
   Atomic::add(*processed, &_symbols_counted);
   Atomic::add(*removed, &_symbols_removed);
   // Exclude printing for normal PrintGCDetails because people parse
   // this output.
   if (PrintGCDetails && Verbose && WizardMode) {
     gclog_or_tty->print(" [Symbols: scanned=%d removed=%d size=" SIZE_FORMAT "K] ", *processed, *removed,
                         (memory_total*HeapWordSize)/1024);
   }
 }
 // Create a new table and using alternate hash code, populate the new table
 // with the existing strings.   Set flag to use the alternate hash code afterwards.
 void SymbolTable::rehash_table() {
   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
   // This should never happen with -Xshare:dump but it might in testing mode.
   if (DumpSharedSpaces) return;
   // Create a new symbol table
   SymbolTable* new_table = new SymbolTable();
   the_table()->move_to(new_table);
   // Delete the table and buckets (entries are reused in new table).
   delete _the_table;
   // Don't check if we need rehashing until the table gets unbalanced again.
   // Then rehash with a new global seed.
   _needs_rehashing = false;
   _the_table = new_table;
 }
 // Lookup a symbol in a bucket.
 Symbol* SymbolTable::lookup(int index, const char* name,
                               int len, unsigned int hash) {
   int count = 0;
   for (HashtableEntry<Symbol*, mtSymbol>* e = bucket(index); e != NULL; e = e->next()) {
     count++;  // count all entries in this bucket, not just ones with same hash
     if (e->hash() == hash) {
       Symbol* sym = e->literal();
       if (sym->equals(name, len)) {
         // something is referencing this symbol now.
         sym->increment_refcount();
         return sym;
       }
     }
   }
   // If the bucket size is too deep check if this hash code is insufficient.
   if (count >= BasicHashtable<mtSymbol>::rehash_count && !needs_rehashing()) {
     _needs_rehashing = check_rehash_table(count);
   }
   return NULL;
 }
 // Pick hashing algorithm.
 unsigned int SymbolTable::hash_symbol(const char* s, int len) {
   return use_alternate_hashcode() ?
            AltHashing::murmur3_32(seed(), (const jbyte*)s, len) :
            java_lang_String::hash_code(s, len);
 }
 // We take care not to be blocking while holding the
 // SymbolTable_lock. Otherwise, the system might deadlock, since the
 // symboltable is used during compilation (VM_thread) The lock free
 // synchronization is simplified by the fact that we do not delete
 // entries in the symbol table during normal execution (only during
 // safepoints).
 Symbol* SymbolTable::lookup(const char* name, int len, TRAPS) {
   unsigned int hashValue = hash_symbol(name, len);
   int index = the_table()->hash_to_index(hashValue);
   Symbol* s = the_table()->lookup(index, name, len, hashValue);
   // Found
   if (s != NULL) return s;
   // Grab SymbolTable_lock first.
   MutexLocker ml(SymbolTable_lock, THREAD);
   // Otherwise, add to symbol to table
   return the_table()->basic_add(index, (u1*)name, len, hashValue, true, CHECK_NULL);
 }
 Symbol* SymbolTable::lookup(const Symbol* sym, int begin, int end, TRAPS) {
   char* buffer;
   int index, len;
   unsigned int hashValue;
   char* name;
   {
     debug_only(No_Safepoint_Verifier nsv;)
     name = (char*)sym->base() + begin;
     len = end - begin;
     hashValue = hash_symbol(name, len);
     index = the_table()->hash_to_index(hashValue);
     Symbol* s = the_table()->lookup(index, name, len, hashValue);
     // Found
     if (s != NULL) return s;
   }
   // Otherwise, add to symbol to table. Copy to a C string first.
   char stack_buf[128];
   ResourceMark rm(THREAD);
   if (len <= 128) {
     buffer = stack_buf;
   } else {
     buffer = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, len);
   }
   for (int i=0; i<len; i++) {
     buffer[i] = name[i];
   }
   // Make sure there is no safepoint in the code above since name can't move.
   // We can't include the code in No_Safepoint_Verifier because of the
   // ResourceMark.
   // Grab SymbolTable_lock first.
   MutexLocker ml(SymbolTable_lock, THREAD);
   return the_table()->basic_add(index, (u1*)buffer, len, hashValue, true, CHECK_NULL);
 }
 Symbol* SymbolTable::lookup_only(const char* name, int len,
                                    unsigned int& hash) {
   hash = hash_symbol(name, len);
   int index = the_table()->hash_to_index(hash);
   Symbol* s = the_table()->lookup(index, name, len, hash);
   return s;
 }
 // Look up the address of the literal in the SymbolTable for this Symbol*
 // Do not create any new symbols
 // Do not increment the reference count to keep this alive
 Symbol** SymbolTable::lookup_symbol_addr(Symbol* sym){
   unsigned int hash = hash_symbol((char*)sym->bytes(), sym->utf8_length());
   int index = the_table()->hash_to_index(hash);
   for (HashtableEntry<Symbol*, mtSymbol>* e = the_table()->bucket(index); e != NULL; e = e->next()) {
     if (e->hash() == hash) {
       Symbol* literal_sym = e->literal();
       if (sym == literal_sym) {
         return e->literal_addr();
       }
     }
   }
   return NULL;
 }
 // Suggestion: Push unicode-based lookup all the way into the hashing
 // and probing logic, so there is no need for convert_to_utf8 until
 // an actual new Symbol* is created.
 Symbol* SymbolTable::lookup_unicode(const jchar* name, int utf16_length, TRAPS) {
   int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
   char stack_buf[128];
   if (utf8_length < (int) sizeof(stack_buf)) {
     char* chars = stack_buf;
     UNICODE::convert_to_utf8(name, utf16_length, chars);
     return lookup(chars, utf8_length, THREAD);
   } else {
     ResourceMark rm(THREAD);
     char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);;
     UNICODE::convert_to_utf8(name, utf16_length, chars);
     return lookup(chars, utf8_length, THREAD);
   }
 }
 Symbol* SymbolTable::lookup_only_unicode(const jchar* name, int utf16_length,
                                            unsigned int& hash) {
   int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
   char stack_buf[128];
   if (utf8_length < (int) sizeof(stack_buf)) {
     char* chars = stack_buf;
     UNICODE::convert_to_utf8(name, utf16_length, chars);
     return lookup_only(chars, utf8_length, hash);
   } else {
     ResourceMark rm;
     char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);;
     UNICODE::convert_to_utf8(name, utf16_length, chars);
     return lookup_only(chars, utf8_length, hash);
   }
 }
 void SymbolTable::add(ClassLoaderData* loader_data, constantPoolHandle cp,
                       int names_count,
                       const char** names, int* lengths, int* cp_indices,
                       unsigned int* hashValues, TRAPS) {
   // Grab SymbolTable_lock first.
   MutexLocker ml(SymbolTable_lock, THREAD);
   SymbolTable* table = the_table();
   bool added = table->basic_add(loader_data, cp, names_count, names, lengths,
                                 cp_indices, hashValues, CHECK);
   if (!added) {
     // do it the hard way
     for (int i=0; i<names_count; i++) {
       int index = table->hash_to_index(hashValues[i]);
       bool c_heap = !loader_data->is_the_null_class_loader_data();
       Symbol* sym = table->basic_add(index, (u1*)names[i], lengths[i], hashValues[i], c_heap, CHECK);
       cp->symbol_at_put(cp_indices[i], sym);
     }
   }
 }
 Symbol* SymbolTable::new_permanent_symbol(const char* name, TRAPS) {
   unsigned int hash;
   Symbol* result = SymbolTable::lookup_only((char*)name, (int)strlen(name), hash);
   if (result != NULL) {
     return result;
   }
   // Grab SymbolTable_lock first.
   MutexLocker ml(SymbolTable_lock, THREAD);
   SymbolTable* table = the_table();
   int index = table->hash_to_index(hash);
   return table->basic_add(index, (u1*)name, (int)strlen(name), hash, false, THREAD);
 }
 Symbol* SymbolTable::basic_add(int index_arg, u1 *name, int len,
                                unsigned int hashValue_arg, bool c_heap, TRAPS) {
   assert(!Universe::heap()->is_in_reserved(name),
          "proposed name of symbol must be stable");
   // Don't allow symbols to be created which cannot fit in a Symbol*.
   if (len > Symbol::max_length()) {
     THROW_MSG_0(vmSymbols::java_lang_InternalError(),
                 "name is too long to represent");
   }
   // Cannot hit a safepoint in this function because the "this" pointer can move.
   No_Safepoint_Verifier nsv;
   // Check if the symbol table has been rehashed, if so, need to recalculate
   // the hash value and index.
   unsigned int hashValue;
   int index;
   if (use_alternate_hashcode()) {
     hashValue = hash_symbol((const char*)name, len);
     index = hash_to_index(hashValue);
   } else {
     hashValue = hashValue_arg;
     index = index_arg;
   }
   // Since look-up was done lock-free, we need to check if another
   // thread beat us in the race to insert the symbol.
   Symbol* test = lookup(index, (char*)name, len, hashValue);
   if (test != NULL) {
     // A race occurred and another thread introduced the symbol.
     assert(test->refcount() != 0, "lookup should have incremented the count");
     return test;
   }
   // Create a new symbol.
   Symbol* sym = allocate_symbol(name, len, c_heap, CHECK_NULL);
   assert(sym->equals((char*)name, len), "symbol must be properly initialized");
   HashtableEntry<Symbol*, mtSymbol>* entry = new_entry(hashValue, sym);
   add_entry(index, entry);
   return sym;
 }
 // This version of basic_add adds symbols in batch from the constant pool
 // parsing.
 bool SymbolTable::basic_add(ClassLoaderData* loader_data, constantPoolHandle cp,
                             int names_count,
                             const char** names, int* lengths,
                             int* cp_indices, unsigned int* hashValues,
                             TRAPS) {
   // Check symbol names are not too long.  If any are too long, don't add any.
   for (int i = 0; i< names_count; i++) {
     if (lengths[i] > Symbol::max_length()) {
       THROW_MSG_0(vmSymbols::java_lang_InternalError(),
                   "name is too long to represent");
     }
   }
   // Cannot hit a safepoint in this function because the "this" pointer can move.
   No_Safepoint_Verifier nsv;
   for (int i=0; i<names_count; i++) {
     // Check if the symbol table has been rehashed, if so, need to recalculate
     // the hash value.
     unsigned int hashValue;
     if (use_alternate_hashcode()) {
       hashValue = hash_symbol(names[i], lengths[i]);
     } else {
       hashValue = hashValues[i];
     }
     // Since look-up was done lock-free, we need to check if another
     // thread beat us in the race to insert the symbol.
     int index = hash_to_index(hashValue);
     Symbol* test = lookup(index, names[i], lengths[i], hashValue);
     if (test != NULL) {
       // A race occurred and another thread introduced the symbol, this one
       // will be dropped and collected. Use test instead.
       cp->symbol_at_put(cp_indices[i], test);
       assert(test->refcount() != 0, "lookup should have incremented the count");
     } else {
       // Create a new symbol.  The null class loader is never unloaded so these
       // are allocated specially in a permanent arena.
       bool c_heap = !loader_data->is_the_null_class_loader_data();
       Symbol* sym = allocate_symbol((const u1*)names[i], lengths[i], c_heap, CHECK_(false));
       assert(sym->equals(names[i], lengths[i]), "symbol must be properly initialized");  // why wouldn't it be???
       HashtableEntry<Symbol*, mtSymbol>* entry = new_entry(hashValue, sym);
       add_entry(index, entry);
       cp->symbol_at_put(cp_indices[i], sym);
     }
   }
   return true;
 }
 void SymbolTable::verify() {
   for (int i = 0; i < the_table()->table_size(); ++i) {
     HashtableEntry<Symbol*, mtSymbol>* p = the_table()->bucket(i);
     for ( ; p != NULL; p = p->next()) {
       Symbol* s = (Symbol*)(p->literal());
       guarantee(s != NULL, "symbol is NULL");
       unsigned int h = hash_symbol((char*)s->bytes(), s->utf8_length());
       guarantee(p->hash() == h, "broken hash in symbol table entry");
       guarantee(the_table()->hash_to_index(h) == i,
                 "wrong index in symbol table");
     }
   }
 }
 void SymbolTable::dump(outputStream* st) {
   the_table()->dump_table(st, "SymbolTable");
 }
 //---------------------------------------------------------------------------
 // Non-product code
 #ifndef PRODUCT
 void SymbolTable::print_histogram() {
   MutexLocker ml(SymbolTable_lock);
   const int results_length = 100;
   int results[results_length];
   int i,j;
   // initialize results to zero
   for (j = 0; j < results_length; j++) {
     results[j] = 0;
   }
   int total = 0;
   int max_symbols = 0;
   int out_of_range = 0;
   int memory_total = 0;
   int count = 0;
   for (i = 0; i < the_table()->table_size(); i++) {
     HashtableEntry<Symbol*, mtSymbol>* p = the_table()->bucket(i);
     for ( ; p != NULL; p = p->next()) {
       memory_total += p->literal()->size();
       count++;
       int counter = p->literal()->utf8_length();
       total += counter;
       if (counter < results_length) {
         results[counter]++;
       } else {
         out_of_range++;
       }
       max_symbols = MAX2(max_symbols, counter);
     }
   }
   tty->print_cr("Symbol Table:");
   tty->print_cr("Total number of symbols  %5d", count);
   tty->print_cr("Total size in memory     %5dK",
           (memory_total*HeapWordSize)/1024);
   tty->print_cr("Total counted            %5d", _symbols_counted);
   tty->print_cr("Total removed            %5d", _symbols_removed);
   if (_symbols_counted > 0) {
     tty->print_cr("Percent removed          %3.2f",
           ((float)_symbols_removed/(float)_symbols_counted)* 100);
   }
   tty->print_cr("Reference counts         %5d", Symbol::_total_count);
   tty->print_cr("Symbol arena size        %5d used %5d",
                  arena()->size_in_bytes(), arena()->used());
   tty->print_cr("Histogram of symbol length:");
   tty->print_cr("%8s %5d", "Total  ", total);
   tty->print_cr("%8s %5d", "Maximum", max_symbols);
   tty->print_cr("%8s %3.2f", "Average",
           ((float) total / (float) the_table()->table_size()));
   tty->print_cr("%s", "Histogram:");
   tty->print_cr(" %s %29s", "Length", "Number chains that length");
   for (i = 0; i < results_length; i++) {
     if (results[i] > 0) {
       tty->print_cr("%6d %10d", i, results[i]);
     }
   }
   if (Verbose) {
     int line_length = 70;
     tty->print_cr("%s %30s", " Length", "Number chains that length");
     for (i = 0; i < results_length; i++) {
       if (results[i] > 0) {
         tty->print("%4d", i);
         for (j = 0; (j < results[i]) && (j < line_length);  j++) {
           tty->print("%1s", "*");
         }
         if (j == line_length) {
           tty->print("%1s", "+");
         }
         tty->cr();
       }
     }
   }
   tty->print_cr(" %s %d: %d\n", "Number chains longer than",
                     results_length, out_of_range);
 }
 void SymbolTable::print() {
   for (int i = 0; i < the_table()->table_size(); ++i) {
     HashtableEntry<Symbol*, mtSymbol>** p = the_table()->bucket_addr(i);
     HashtableEntry<Symbol*, mtSymbol>* entry = the_table()->bucket(i);
     if (entry != NULL) {
       while (entry != NULL) {
         tty->print(PTR_FORMAT " ", entry->literal());
         entry->literal()->print();
         tty->print(" %d", entry->literal()->refcount());
         p = entry->next_addr();
         entry = (HashtableEntry<Symbol*, mtSymbol>*)HashtableEntry<Symbol*, mtSymbol>::make_ptr(*p);
       }
       tty->cr();
     }
   }
 }
 #endif // PRODUCT
 // --------------------------------------------------------------------------
 #ifdef ASSERT
 class StableMemoryChecker : public StackObj {
   enum { _bufsize = wordSize*4 };
   address _region;
   jint    _size;
   u1      _save_buf[_bufsize];
   int sample(u1* save_buf) {
     if (_size <= _bufsize) {
       memcpy(save_buf, _region, _size);
       return _size;
     } else {
       // copy head and tail
       memcpy(&save_buf[0],          _region,                      _bufsize/2);
       memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);
       return (_bufsize/2)*2;
     }
   }
  public:
   StableMemoryChecker(const void* region, jint size) {
     _region = (address) region;
     _size   = size;
     sample(_save_buf);
   }
   bool verify() {
     u1 check_buf[sizeof(_save_buf)];
     int check_size = sample(check_buf);
     return (0 == memcmp(_save_buf, check_buf, check_size));
   }
   void set_region(const void* region) { _region = (address) region; }
 };
 #endif
 // --------------------------------------------------------------------------
 StringTable* StringTable::_the_table = NULL;
 bool StringTable::_needs_rehashing = false;
 volatile int StringTable::_parallel_claimed_idx = 0;
 // Pick hashing algorithm
 unsigned int StringTable::hash_string(const jchar* s, int len) {
   return use_alternate_hashcode() ? AltHashing::murmur3_32(seed(), s, len) :
                                     java_lang_String::hash_code(s, len);
 }
 oop StringTable::lookup(int index, jchar* name,
                         int len, unsigned int hash) {
   int count = 0;
   for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) {
     count++;
     if (l->hash() == hash) {
       if (java_lang_String::equals(l->literal(), name, len)) {
         return l->literal();
       }
     }
   }
   // If the bucket size is too deep check if this hash code is insufficient.
   if (count >= BasicHashtable<mtSymbol>::rehash_count && !needs_rehashing()) {
     _needs_rehashing = check_rehash_table(count);
   }
   return NULL;
 }
 oop StringTable::basic_add(int index_arg, Handle string, jchar* name,
                            int len, unsigned int hashValue_arg, TRAPS) {
   assert(java_lang_String::equals(string(), name, len),
          "string must be properly initialized");
   // Cannot hit a safepoint in this function because the "this" pointer can move.
   No_Safepoint_Verifier nsv;
   // Check if the symbol table has been rehashed, if so, need to recalculate
   // the hash value and index before second lookup.
   unsigned int hashValue;
   int index;
   if (use_alternate_hashcode()) {
     hashValue = hash_string(name, len);
     index = hash_to_index(hashValue);
   } else {
     hashValue = hashValue_arg;
     index = index_arg;
   }
   // Since look-up was done lock-free, we need to check if another
   // thread beat us in the race to insert the symbol.
   oop test = lookup(index, name, len, hashValue); // calls lookup(u1*, int)
   if (test != NULL) {
     // Entry already added
     return test;
   }
   HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string());
   add_entry(index, entry);
   return string();
 }
 oop StringTable::lookup(Symbol* symbol) {
   ResourceMark rm;
   int length;
   jchar* chars = symbol->as_unicode(length);
   return lookup(chars, length);
 }
 oop StringTable::lookup(jchar* name, int len) {
   unsigned int hash = hash_string(name, len);
   int index = the_table()->hash_to_index(hash);
   return the_table()->lookup(index, name, len, hash);
 }
 oop StringTable::intern(Handle string_or_null, jchar* name,
                         int len, TRAPS) {
   unsigned int hashValue = hash_string(name, len);
   int index = the_table()->hash_to_index(hashValue);
   oop found_string = the_table()->lookup(index, name, len, hashValue);
   // Found
   if (found_string != NULL) return found_string;
   debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));
   assert(!Universe::heap()->is_in_reserved(name),
          "proposed name of symbol must be stable");
   Handle string;
   // try to reuse the string if possible
   if (!string_or_null.is_null()) {
     string = string_or_null;
   } else {
     string = java_lang_String::create_from_unicode(name, len, CHECK_NULL);
   }
 #if INCLUDE_ALL_GCS
   if (G1StringDedup::is_enabled()) {
     // Deduplicate the string before it is interned. Note that we should never
     // deduplicate a string after it has been interned. Doing so will counteract
     // compiler optimizations done on e.g. interned string literals.
     G1StringDedup::deduplicate(string());
   }
 #endif
   // Grab the StringTable_lock before getting the_table() because it could
   // change at safepoint.
   MutexLocker ml(StringTable_lock, THREAD);
   // Otherwise, add to symbol to table
   return the_table()->basic_add(index, string, name, len,
                                 hashValue, CHECK_NULL);
 }
 oop StringTable::intern(Symbol* symbol, TRAPS) {
   if (symbol == NULL) return NULL;
   ResourceMark rm(THREAD);
   int length;
   jchar* chars = symbol->as_unicode(length);
   Handle string;
   oop result = intern(string, chars, length, CHECK_NULL);
   return result;
 }
 oop StringTable::intern(oop string, TRAPS)
 {
   if (string == NULL) return NULL;
   ResourceMark rm(THREAD);
   int length;
   Handle h_string (THREAD, string);
   jchar* chars = java_lang_String::as_unicode_string(string, length, CHECK_NULL);
   oop result = intern(h_string, chars, length, CHECK_NULL);
   return result;
 }
 oop StringTable::intern(const char* utf8_string, TRAPS) {
   if (utf8_string == NULL) return NULL;
   ResourceMark rm(THREAD);
   int length = UTF8::unicode_length(utf8_string);
   jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
   UTF8::convert_to_unicode(utf8_string, chars, length);
   Handle string;
   oop result = intern(string, chars, length, CHECK_NULL);
   return result;
 }
 void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
   buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), processed, removed);
 }
 void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
   // Readers of the table are unlocked, so we should only be removing
   // entries at a safepoint.
   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
   const int limit = the_table()->table_size();
   for (;;) {
     // Grab next set of buckets to scan
     int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
     if (start_idx >= limit) {
       // End of table
       break;
     }
     int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
     buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, processed, removed);
   }
 }
 void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) {
   const int limit = the_table()->table_size();
   assert(0 <= start_idx && start_idx <= limit,
          err_msg("start_idx (" INT32_FORMAT ") is out of bounds", start_idx));
   assert(0 <= end_idx && end_idx <= limit,
          err_msg("end_idx (" INT32_FORMAT ") is out of bounds", end_idx));
   assert(start_idx <= end_idx,
          err_msg("Index ordering: start_idx=" INT32_FORMAT", end_idx=" INT32_FORMAT,
                  start_idx, end_idx));
   for (int i = start_idx; i < end_idx; i += 1) {
     HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
     while (entry != NULL) {
       assert(!entry->is_shared(), "CDS not used for the StringTable");
       f->do_oop((oop*)entry->literal_addr());
       entry = entry->next();
     }
   }
 }
 void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed) {
   const int limit = the_table()->table_size();
   assert(0 <= start_idx && start_idx <= limit,
          err_msg("start_idx (" INT32_FORMAT ") is out of bounds", start_idx));
   assert(0 <= end_idx && end_idx <= limit,
          err_msg("end_idx (" INT32_FORMAT ") is out of bounds", end_idx));
   assert(start_idx <= end_idx,
          err_msg("Index ordering: start_idx=" INT32_FORMAT", end_idx=" INT32_FORMAT,
                  start_idx, end_idx));
   for (int i = start_idx; i < end_idx; ++i) {
     HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i);
     HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
     while (entry != NULL) {
       assert(!entry->is_shared(), "CDS not used for the StringTable");
       if (is_alive->do_object_b(entry->literal())) {
         if (f != NULL) {
           f->do_oop((oop*)entry->literal_addr());
         }
         p = entry->next_addr();
       } else {
         *p = entry->next();
         the_table()->free_entry(entry);
         (*removed)++;
       }
       (*processed)++;
       entry = *p;
     }
   }
 }
 void StringTable::oops_do(OopClosure* f) {
   buckets_oops_do(f, 0, the_table()->table_size());
 }
 void StringTable::possibly_parallel_oops_do(OopClosure* f) {
   const int limit = the_table()->table_size();
   for (;;) {
     // Grab next set of buckets to scan
     int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
     if (start_idx >= limit) {
       // End of table
       break;
     }
     int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
     buckets_oops_do(f, start_idx, end_idx);
   }
 }
 // This verification is part of Universe::verify() and needs to be quick.
 // See StringTable::verify_and_compare() below for exhaustive verification.
 void StringTable::verify() {
   for (int i = 0; i < the_table()->table_size(); ++i) {
     HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
     for ( ; p != NULL; p = p->next()) {
       oop s = p->literal();
       guarantee(s != NULL, "interned string is NULL");
       unsigned int h = java_lang_String::hash_string(s);
       guarantee(p->hash() == h, "broken hash in string table entry");
       guarantee(the_table()->hash_to_index(h) == i,
                 "wrong index in string table");
     }
   }
 }
 void StringTable::dump(outputStream* st) {
   the_table()->dump_table(st, "StringTable");
 }
 StringTable::VerifyRetTypes StringTable::compare_entries(
                                       int bkt1, int e_cnt1,
                                       HashtableEntry<oop, mtSymbol>* e_ptr1,
                                       int bkt2, int e_cnt2,
                                       HashtableEntry<oop, mtSymbol>* e_ptr2) {
   // These entries are sanity checked by verify_and_compare_entries()
   // before this function is called.
   oop str1 = e_ptr1->literal();
   oop str2 = e_ptr2->literal();
   if (str1 == str2) {
     tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") "
                   "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]",
                   (void *)str1, bkt1, e_cnt1, bkt2, e_cnt2);
     return _verify_fail_continue;
   }
   if (java_lang_String::equals(str1, str2)) {
     tty->print_cr("ERROR: identical String values in entry @ "
                   "bucket[%d][%d] and entry @ bucket[%d][%d]",
                   bkt1, e_cnt1, bkt2, e_cnt2);
     return _verify_fail_continue;
   }
   return _verify_pass;
 }
 StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt,
                                       HashtableEntry<oop, mtSymbol>* e_ptr,
                                       StringTable::VerifyMesgModes mesg_mode) {
   VerifyRetTypes ret = _verify_pass;  // be optimistic
   oop str = e_ptr->literal();
   if (str == NULL) {
     if (mesg_mode == _verify_with_mesgs) {
       tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt,
                     e_cnt);
     }
     // NULL oop means no more verifications are possible
     return _verify_fail_done;
   }
   if (str->klass() != SystemDictionary::String_klass()) {
     if (mesg_mode == _verify_with_mesgs) {
       tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]",
                     bkt, e_cnt);
     }
     // not a String means no more verifications are possible
     return _verify_fail_done;
   }
   unsigned int h = java_lang_String::hash_string(str);
   if (e_ptr->hash() != h) {
     if (mesg_mode == _verify_with_mesgs) {
       tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], "
                     "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h);
     }
     ret = _verify_fail_continue;
   }
   if (the_table()->hash_to_index(h) != bkt) {
     if (mesg_mode == _verify_with_mesgs) {
       tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], "
                     "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h,
                     the_table()->hash_to_index(h));
     }
     ret = _verify_fail_continue;
   }
   return ret;
 }
 // See StringTable::verify() above for the quick verification that is
 // part of Universe::verify(). This verification is exhaustive and
 // reports on every issue that is found. StringTable::verify() only
 // reports on the first issue that is found.
 //
 // StringTable::verify_entry() checks:
 // - oop value != NULL (same as verify())
 // - oop value is a String
 // - hash(String) == hash in entry (same as verify())
 // - index for hash == index of entry (same as verify())
 //
 // StringTable::compare_entries() checks:
 // - oops are unique across all entries
 // - String values are unique across all entries
 //
 int StringTable::verify_and_compare_entries() {
   assert(StringTable_lock->is_locked(), "sanity check");
   int  fail_cnt = 0;
   // first, verify all the entries individually:
   for (int bkt = 0; bkt < the_table()->table_size(); bkt++) {
     HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt);
     for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) {
       VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs);
       if (ret != _verify_pass) {
         fail_cnt++;
       }
     }
   }
   // Optimization: if the above check did not find any failures, then
   // the comparison loop below does not need to call verify_entry()
   // before calling compare_entries(). If there were failures, then we
   // have to call verify_entry() to see if the entry can be passed to
   // compare_entries() safely. When we call verify_entry() in the loop
   // below, we do so quietly to void duplicate messages and we don't
   // increment fail_cnt because the failures have already been counted.
   bool need_entry_verify = (fail_cnt != 0);
   // second, verify all entries relative to each other:
   for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) {
     HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1);
     for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) {
       if (need_entry_verify) {
         VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1,
                                           _verify_quietly);
         if (ret == _verify_fail_done) {
           // cannot use the current entry to compare against other entries
           continue;
         }
       }
       for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) {
         HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2);
         int e_cnt2;
         for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) {
           if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) {
             // skip the entries up to and including the one that
             // we're comparing against
             continue;
           }
           if (need_entry_verify) {
             VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2,
                                               _verify_quietly);
             if (ret == _verify_fail_done) {
               // cannot compare against this entry
               continue;
             }
           }
           // compare two entries, report and count any failures:
           if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2)
               != _verify_pass) {
             fail_cnt++;
           }
         }
       }
     }
   }
   return fail_cnt;
 }
 // Create a new table and using alternate hash code, populate the new table
 // with the existing strings.   Set flag to use the alternate hash code afterwards.
 void StringTable::rehash_table() {
   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
   // This should never happen with -Xshare:dump but it might in testing mode.
   if (DumpSharedSpaces) return;
   StringTable* new_table = new StringTable();
   // Rehash the table
   the_table()->move_to(new_table);
   // Delete the table and buckets (entries are reused in new table).
   delete _the_table;
   // Don't check if we need rehashing until the table gets unbalanced again.
   // Then rehash with a new global seed.
   _needs_rehashing = false;
   _the_table = new_table;
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/classfile/symbolTable.cpp@595c0f60d50d (annotated)

src/share/vm/classfile/symbolTable.cpp