| /* |
| * Copyright (c) 1997, 2017, 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/g1SATBCardTableModRefBS.hpp" |
| #include "gc_implementation/g1/g1StringDedup.hpp" |
| #endif |
| |
| PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC |
| |
| // -------------------------------------------------------------------------- |
| |
| // 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(mtSymbol); |
| } else { |
| _arena = new (mtSymbol) Arena(mtSymbol, 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, BucketUnlinkContext* context, 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(); |
| context->_num_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; |
| *p = entry->next(); |
| context->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; |
| BucketUnlinkContext context; |
| buckets_unlink(0, the_table()->table_size(), &context, &memory_total); |
| _the_table->bulk_free_entries(&context); |
| *processed = context._num_processed; |
| *removed = context._num_removed; |
| |
| _symbols_removed = context._num_removed; |
| _symbols_counted = context._num_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; |
| |
| BucketUnlinkContext context; |
| 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, &context, &memory_total); |
| } |
| |
| _the_table->bulk_free_entries(&context); |
| *processed = context._num_processed; |
| *removed = context._num_removed; |
| |
| Atomic::add(context._num_processed, &_symbols_counted); |
| Atomic::add(context._num_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 >= 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 >= 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); |
| } |
| |
| // Tell the GC that this string was looked up in the StringTable. |
| static void ensure_string_alive(oop string) { |
| // A lookup in the StringTable could return an object that was previously |
| // considered dead. The SATB part of G1 needs to get notified about this |
| // potential resurrection, otherwise the marking might not find the object. |
| #if INCLUDE_ALL_GCS |
| if (UseG1GC && string != NULL) { |
| G1SATBCardTableModRefBS::enqueue(string); |
| } |
| #endif |
| } |
| |
| oop StringTable::lookup(jchar* name, int len) { |
| unsigned int hash = hash_string(name, len); |
| int index = the_table()->hash_to_index(hash); |
| oop string = the_table()->lookup(index, name, len, hash); |
| |
| ensure_string_alive(string); |
| |
| return string; |
| } |
| |
| |
| 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) { |
| ensure_string_alive(found_string); |
| 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. |
| oop added_or_found; |
| { |
| MutexLocker ml(StringTable_lock, THREAD); |
| // Otherwise, add to symbol to table |
| added_or_found = the_table()->basic_add(index, string, name, len, |
| hashValue, CHECK_NULL); |
| } |
| |
| ensure_string_alive(added_or_found); |
| |
| return added_or_found; |
| } |
| |
| 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) { |
| BucketUnlinkContext context; |
| buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), &context); |
| _the_table->bulk_free_entries(&context); |
| *processed = context._num_processed; |
| *removed = context._num_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(); |
| |
| BucketUnlinkContext context; |
| 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, &context); |
| } |
| _the_table->bulk_free_entries(&context); |
| *processed = context._num_processed; |
| *removed = context._num_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, BucketUnlinkContext* context) { |
| 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(); |
| context->free_entry(entry); |
| } |
| context->_num_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; |
| } |