jdk8-mips64-public/hotspot: src/share/vm/classfile/symbolTable.cpp@3582bf76420e (annotated)

src/share/vm/classfile/symbolTable.cpp@3582bf76420e (annotated)

src/share/vm/classfile/symbolTable.cpp

Thu, 27 Jan 2011 16:11:27 -0800

author: coleenp
date: Thu, 27 Jan 2011 16:11:27 -0800
changeset 2497: 3582bf76420e
parent 2314: f95d63e2154a
child 2618: df1347358fe6
permissions: -rw-r--r--

6990754: Use native memory and reference counting to implement SymbolTable
Summary: move symbols from permgen into C heap and reference count them
Reviewed-by: never, acorn, jmasa, stefank

 /*
  * Copyright (c) 1997, 2010, 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/javaClasses.hpp"
 #include "classfile/symbolTable.hpp"
 #include "classfile/systemDictionary.hpp"
 #include "gc_interface/collectedHeap.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"
 // --------------------------------------------------------------------------
 SymbolTable* SymbolTable::_the_table = NULL;
 Symbol* SymbolTable::allocate_symbol(const u1* name, int len, TRAPS) {
   // 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");
   }
   Symbol* sym = new (len) Symbol(name, len);
   assert(sym != NULL, "new should call vm_exit_out_of_memory if C_HEAP is exhausted");
   return sym;
 }
 bool SymbolTable::allocate_symbols(int names_count, const u1** names,
                                    int* lengths, Symbol** syms, TRAPS) {
   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");
     }
   }
   for (int i = 0; i< names_count; i++) {
     int len = lengths[i];
     syms[i] = new (len) Symbol(names[i], len);
     assert(syms[i] != NULL, "new should call vm_exit_out_of_memory if "
                             "C_HEAP is exhausted");
   }
   return true;
 }
 // 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*>* 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;
 // Remove unreferenced symbols from the symbol table
 // This is done late during GC.  This doesn't use the hash table unlink because
 // it assumes that the literals are oops.
 void SymbolTable::unlink() {
   int removed = 0;
   int total = 0;
   int memory_total = 0;
   for (int i = 0; i < the_table()->table_size(); ++i) {
     for (HashtableEntry<Symbol*>** p = the_table()->bucket_addr(i); *p != NULL; ) {
       HashtableEntry<Symbol*>* entry = *p;
       if (entry->is_shared()) {
         break;
       }
       Symbol* s = entry->literal();
       memory_total += s->object_size();
       total++;
       assert(s != NULL, "just checking");
       // If reference count is zero, remove.
       if (s->refcount() == 0) {
         delete s;
         removed++;
         *p = entry->next();
         the_table()->free_entry(entry);
       } else {
         p = entry->next_addr();
       }
     }
   }
   symbols_removed += removed;
   symbols_counted += total;
   if (PrintGCDetails) {
     gclog_or_tty->print(" [Symbols=%d size=%dK] ", total,
                         (memory_total*HeapWordSize)/1024);
   }
 }
 // Lookup a symbol in a bucket.
 Symbol* SymbolTable::lookup(int index, const char* name,
                               int len, unsigned int hash) {
   for (HashtableEntry<Symbol*>* e = bucket(index); e != NULL; e = e->next()) {
     if (e->hash() == hash) {
       Symbol* sym = e->literal();
       if (sym->equals(name, len)) {
         // something is referencing this symbol now.
         sym->increment_refcount();
         return sym;
       }
     }
   }
   return NULL;
 }
 // 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;
   // Otherwise, add to symbol to table
   return the_table()->basic_add(index, (u1*)name, len, hashValue, 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.
   return the_table()->basic_add(index, (u1*)buffer, len, hashValue, 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;
 }
 // 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(constantPoolHandle cp, int names_count,
                       const char** names, int* lengths, int* cp_indices,
                       unsigned int* hashValues, TRAPS) {
   SymbolTable* table = the_table();
   bool added = table->basic_add(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]);
       Symbol* sym = table->basic_add(index, (u1*)names[i], lengths[i],
                                        hashValues[i], CHECK);
       cp->symbol_at_put(cp_indices[i], sym);
     }
   }
 }
 Symbol* SymbolTable::basic_add(int index, u1 *name, int len,
                                  unsigned int hashValue, TRAPS) {
   assert(!Universe::heap()->is_in_reserved(name) || GC_locker::is_active(),
          "proposed name of symbol must be stable");
   // We assume that lookup() has been called already, that it failed,
   // and symbol was not found.  We create the symbol here.
   Symbol* sym = allocate_symbol(name, len, CHECK_NULL);
   // Allocation must be done before grabbing the SymbolTable_lock lock
   MutexLocker ml(SymbolTable_lock, THREAD);
   assert(sym->equals((char*)name, len), "symbol must be properly initialized");
   // 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, this one
     // will be dropped and collected.
     delete sym;
     assert(test->refcount() != 0, "lookup should have incremented the count");
     return test;
   }
   HashtableEntry<Symbol*>* entry = new_entry(hashValue, sym);
   sym->increment_refcount();
   add_entry(index, entry);
   return sym;
 }
 bool SymbolTable::basic_add(constantPoolHandle cp, int names_count,
                             const char** names, int* lengths,
                             int* cp_indices, unsigned int* hashValues,
                             TRAPS) {
   Symbol* syms[symbol_alloc_batch_size];
   bool allocated = allocate_symbols(names_count, (const u1**)names, lengths,
                                     syms, CHECK_false);
   if (!allocated) {
     return false;
   }
   // Allocation must be done before grabbing the SymbolTable_lock lock
   MutexLocker ml(SymbolTable_lock, THREAD);
   for (int i=0; i<names_count; i++) {
     assert(syms[i]->equals(names[i], lengths[i]), "symbol must be properly initialized");
     // 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(hashValues[i]);
     Symbol* test = lookup(index, names[i], lengths[i], hashValues[i]);
     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");
       delete syms[i];
     } else {
       Symbol* sym = syms[i];
       HashtableEntry<Symbol*>* entry = new_entry(hashValues[i], sym);
       sym->increment_refcount();  // increment refcount in external hashtable
       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*>* 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");
     }
   }
 }
 //---------------------------------------------------------------------------
 // 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*>* p = the_table()->bucket(i);
     for ( ; p != NULL; p = p->next()) {
       memory_total += p->literal()->object_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("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*>** p = the_table()->bucket_addr(i);
     HashtableEntry<Symbol*>* 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*>*)HashtableEntry<Symbol*>::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
 // --------------------------------------------------------------------------
 // Compute the hash value for a java.lang.String object which would
 // contain the characters passed in. This hash value is used for at
 // least two purposes.
 //
 // (a) As the hash value used by the StringTable for bucket selection
 //     and comparison (stored in the HashtableEntry structures).  This
 //     is used in the String.intern() method.
 //
 // (b) As the hash value used by the String object itself, in
 //     String.hashCode().  This value is normally calculate in Java code
 //     in the String.hashCode method(), but is precomputed for String
 //     objects in the shared archive file.
 //
 //     For this reason, THIS ALGORITHM MUST MATCH String.hashCode().
 int StringTable::hash_string(jchar* s, int len) {
   unsigned h = 0;
   while (len-- > 0) {
     h = 31*h + (unsigned) *s;
     s++;
   }
   return h;
 }
 StringTable* StringTable::_the_table = NULL;
 oop StringTable::lookup(int index, jchar* name,
                         int len, unsigned int hash) {
   for (HashtableEntry<oop>* l = bucket(index); l != NULL; l = l->next()) {
     if (l->hash() == hash) {
       if (java_lang_String::equals(l->literal(), name, len)) {
         return l->literal();
       }
     }
   }
   return NULL;
 }
 oop StringTable::basic_add(int index, Handle string_or_null, jchar* name,
                            int len, unsigned int hashValue, TRAPS) {
   debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));
   assert(!Universe::heap()->is_in_reserved(name) || GC_locker::is_active(),
          "proposed name of symbol must be stable");
   Handle string;
   // try to reuse the string if possible
   if (!string_or_null.is_null() && string_or_null()->is_perm()) {
     string = string_or_null;
   } else {
     string = java_lang_String::create_tenured_from_unicode(name, len, CHECK_NULL);
   }
   // Allocation must be done before grapping the SymbolTable_lock lock
   MutexLocker ml(StringTable_lock, THREAD);
   assert(java_lang_String::equals(string(), name, len),
          "string must be properly initialized");
   // 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>* 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);
   unsigned int hashValue = hash_string(chars, length);
   int index = the_table()->hash_to_index(hashValue);
   return the_table()->lookup(index, chars, length, hashValue);
 }
 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 string = the_table()->lookup(index, name, len, hashValue);
   // Found
   if (string != NULL) return string;
   // Otherwise, add to symbol to table
   return the_table()->basic_add(index, string_or_null, 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);
   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(BoolObjectClosure* is_alive) {
   // 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");
   for (int i = 0; i < the_table()->table_size(); ++i) {
     for (HashtableEntry<oop>** p = the_table()->bucket_addr(i); *p != NULL; ) {
       HashtableEntry<oop>* entry = *p;
       if (entry->is_shared()) {
         break;
       }
       assert(entry->literal() != NULL, "just checking");
       if (is_alive->do_object_b(entry->literal())) {
         p = entry->next_addr();
       } else {
         *p = entry->next();
         the_table()->free_entry(entry);
       }
     }
   }
 }
 void StringTable::oops_do(OopClosure* f) {
   for (int i = 0; i < the_table()->table_size(); ++i) {
     HashtableEntry<oop>** p = the_table()->bucket_addr(i);
     HashtableEntry<oop>* entry = the_table()->bucket(i);
     while (entry != NULL) {
       f->do_oop((oop*)entry->literal_addr());
       // Did the closure remove the literal from the table?
       if (entry->literal() == NULL) {
         assert(!entry->is_shared(), "immutable hashtable entry?");
         *p = entry->next();
         the_table()->free_entry(entry);
       } else {
         p = entry->next_addr();
       }
       entry = (HashtableEntry<oop>*)HashtableEntry<oop>::make_ptr(*p);
     }
   }
 }
 void StringTable::verify() {
   for (int i = 0; i < the_table()->table_size(); ++i) {
     HashtableEntry<oop>* p = the_table()->bucket(i);
     for ( ; p != NULL; p = p->next()) {
       oop s = p->literal();
       guarantee(s != NULL, "interned string is NULL");
       guarantee(s->is_perm(), "interned string not in permspace");
       int length;
       jchar* chars = java_lang_String::as_unicode_string(s, length);
       unsigned int h = hash_string(chars, length);
       guarantee(p->hash() == h, "broken hash in string table entry");
       guarantee(the_table()->hash_to_index(h) == i,
                 "wrong index in string table");
     }
   }
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/classfile/symbolTable.cpp@3582bf76420e (annotated)

src/share/vm/classfile/symbolTable.cpp