Mercurial > hg > truffle
view src/share/vm/classfile/symbolTable.cpp @ 8938:78bf450b45b9
Remove unused packages
author | Christos Kotselidis <christos.kotselidis@oracle.com> |
---|---|
date | Tue, 09 Apr 2013 11:38:46 +0200 |
parents | ede380e13960 |
children | f258c5828eb8 |
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/* * Copyright (c) 1997, 2013, 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" #include "utilities/numberSeq.hpp" // -------------------------------------------------------------------------- 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; // Remove unreferenced symbols from the symbol table // This is done late during GC. void SymbolTable::unlink() { int removed = 0; int total = 0; size_t memory_total = 0; 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); 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(); total++; 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); } } symbols_removed += removed; symbols_counted += total; // Exclude printing for normal PrintGCDetails because people parse // this output. if (PrintGCDetails && Verbose && WizardMode) { gclog_or_tty->print(" [Symbols=%d size=" SIZE_FORMAT "K] ", total, (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) || GC_locker::is_active(), "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) { NumberSeq summary; for (int i = 0; i < the_table()->table_size(); ++i) { int count = 0; for (HashtableEntry<Symbol*, mtSymbol>* e = the_table()->bucket(i); e != NULL; e = e->next()) { count++; } summary.add((double)count); } st->print_cr("SymbolTable statistics:"); st->print_cr("Number of buckets : %7d", summary.num()); st->print_cr("Average bucket size : %7.0f", summary.avg()); st->print_cr("Variance of bucket size : %7.0f", summary.variance()); st->print_cr("Std. dev. of bucket size: %7.0f", summary.sd()); st->print_cr("Maximum bucket size : %7.0f", summary.maximum()); } //--------------------------------------------------------------------------- // 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; // 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) || 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 = string_or_null; } else { string = java_lang_String::create_from_unicode(name, len, CHECK_NULL); } // 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); 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) { HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i); HashtableEntry<oop, 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; } assert(entry->literal() != NULL, "just checking"); if (entry->is_shared() || is_alive->do_object_b(entry->literal())) { p = entry->next_addr(); } else { *p = entry->next(); the_table()->free_entry(entry); } entry = (HashtableEntry<oop, mtSymbol>*)HashtableEntry<oop, mtSymbol>::make_ptr(*p); } } } void StringTable::oops_do(OopClosure* f) { for (int i = 0; i < the_table()->table_size(); ++i) { HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i); HashtableEntry<oop, mtSymbol>* 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, mtSymbol>*)HashtableEntry<oop, mtSymbol>::make_ptr(*p); } } } 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) { NumberSeq summary; for (int i = 0; i < the_table()->table_size(); ++i) { HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i); int count = 0; for ( ; p != NULL; p = p->next()) { count++; } summary.add((double)count); } st->print_cr("StringTable statistics:"); st->print_cr("Number of buckets : %7d", summary.num()); st->print_cr("Average bucket size : %7.0f", summary.avg()); st->print_cr("Variance of bucket size : %7.0f", summary.variance()); st->print_cr("Std. dev. of bucket size: %7.0f", summary.sd()); st->print_cr("Maximum bucket size : %7.0f", summary.maximum()); } // 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; }