--- /dev/null 2014-05-02 11:38:41.000000000 -0500 +++ new/src/share/vm/classfile/stringTable.cpp 2014-05-02 11:38:41.000000000 -0500 @@ -0,0 +1,531 @@ +/* + * 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/stringTable.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; + +#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* 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::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* 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 (%d) is out of bounds", start_idx)); + assert(0 <= end_idx && end_idx <= limit, + err_msg("end_idx (%d) is out of bounds", end_idx)); + assert(start_idx <= end_idx, + err_msg("Index ordering: start_idx=%d, end_idx=%d", + start_idx, end_idx)); + + for (int i = start_idx; i < end_idx; i += 1) { + HashtableEntry* 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 (%d) is out of bounds", start_idx)); + assert(0 <= end_idx && end_idx <= limit, + err_msg("end_idx (%d) is out of bounds", end_idx)); + assert(start_idx <= end_idx, + err_msg("Index ordering: start_idx=%d, end_idx=%d", + start_idx, end_idx)); + + for (int i = start_idx; i < end_idx; ++i) { + HashtableEntry** p = the_table()->bucket_addr(i); + HashtableEntry* 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* 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* e_ptr1, + int bkt2, int e_cnt2, + HashtableEntry* 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* 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* 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* 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* 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; +}