--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/classfile/stringTable.cpp Mon May 12 09:47:57 2014 -0400
@@ -0,0 +1,533 @@
+/*
+ * 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
+
+PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
+
+// 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<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) {
+ count++;
+ if (l->hash() == hash) {
+ if (java_lang_String::equals(l->literal(), name, len)) {
+ return l->literal();
+ }
+ }
+ }
+ // If the bucket size is too deep check if this hash code is insufficient.
+ if (count >= BasicHashtable<mtSymbol>::rehash_count && !needs_rehashing()) {
+ _needs_rehashing = check_rehash_table(count);
+ }
+ return NULL;
+}
+
+
+oop StringTable::basic_add(int index_arg, Handle string, jchar* name,
+ int len, unsigned int hashValue_arg, TRAPS) {
+
+ assert(java_lang_String::equals(string(), name, len),
+ "string must be properly initialized");
+ // Cannot hit a safepoint in this function because the "this" pointer can move.
+ No_Safepoint_Verifier nsv;
+
+ // Check if the symbol table has been rehashed, if so, need to recalculate
+ // the hash value and index before second lookup.
+ unsigned int hashValue;
+ int index;
+ if (use_alternate_hashcode()) {
+ hashValue = hash_string(name, len);
+ index = hash_to_index(hashValue);
+ } else {
+ hashValue = hashValue_arg;
+ index = index_arg;
+ }
+
+ // Since look-up was done lock-free, we need to check if another
+ // thread beat us in the race to insert the symbol.
+
+ oop test = lookup(index, name, len, hashValue); // calls lookup(u1*, int)
+ if (test != NULL) {
+ // Entry already added
+ return test;
+ }
+
+ HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string());
+ add_entry(index, entry);
+ return string();
+}
+
+
+oop StringTable::lookup(Symbol* symbol) {
+ ResourceMark rm;
+ int length;
+ jchar* chars = symbol->as_unicode(length);
+ return lookup(chars, length);
+}
+
+
+oop StringTable::lookup(jchar* name, int len) {
+ unsigned int hash = hash_string(name, len);
+ int index = the_table()->hash_to_index(hash);
+ return the_table()->lookup(index, name, len, hash);
+}
+
+
+oop StringTable::intern(Handle string_or_null, jchar* name,
+ int len, TRAPS) {
+ unsigned int hashValue = hash_string(name, len);
+ int index = the_table()->hash_to_index(hashValue);
+ oop found_string = the_table()->lookup(index, name, len, hashValue);
+
+ // Found
+ if (found_string != NULL) return found_string;
+
+ debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));
+ assert(!Universe::heap()->is_in_reserved(name),
+ "proposed name of symbol must be stable");
+
+ Handle string;
+ // try to reuse the string if possible
+ if (!string_or_null.is_null()) {
+ string = string_or_null;
+ } else {
+ string = java_lang_String::create_from_unicode(name, len, CHECK_NULL);
+ }
+
+#if INCLUDE_ALL_GCS
+ if (G1StringDedup::is_enabled()) {
+ // Deduplicate the string before it is interned. Note that we should never
+ // deduplicate a string after it has been interned. Doing so will counteract
+ // compiler optimizations done on e.g. interned string literals.
+ G1StringDedup::deduplicate(string());
+ }
+#endif
+
+ // Grab the StringTable_lock before getting the_table() because it could
+ // change at safepoint.
+ MutexLocker ml(StringTable_lock, THREAD);
+
+ // Otherwise, add to symbol to table
+ return the_table()->basic_add(index, string, name, len,
+ hashValue, CHECK_NULL);
+}
+
+oop StringTable::intern(Symbol* symbol, TRAPS) {
+ if (symbol == NULL) return NULL;
+ ResourceMark rm(THREAD);
+ int length;
+ jchar* chars = symbol->as_unicode(length);
+ Handle string;
+ oop result = intern(string, chars, length, CHECK_NULL);
+ return result;
+}
+
+
+oop StringTable::intern(oop string, TRAPS)
+{
+ if (string == NULL) return NULL;
+ ResourceMark rm(THREAD);
+ int length;
+ Handle h_string (THREAD, string);
+ jchar* chars = java_lang_String::as_unicode_string(string, length, CHECK_NULL);
+ oop result = intern(h_string, chars, length, CHECK_NULL);
+ return result;
+}
+
+
+oop StringTable::intern(const char* utf8_string, TRAPS) {
+ if (utf8_string == NULL) return NULL;
+ ResourceMark rm(THREAD);
+ int length = UTF8::unicode_length(utf8_string);
+ jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
+ UTF8::convert_to_unicode(utf8_string, chars, length);
+ Handle string;
+ oop result = intern(string, chars, length, CHECK_NULL);
+ return result;
+}
+
+void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
+ buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), processed, removed);
+}
+
+void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
+ // Readers of the table are unlocked, so we should only be removing
+ // entries at a safepoint.
+ assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+ const int limit = the_table()->table_size();
+
+ for (;;) {
+ // Grab next set of buckets to scan
+ int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
+ if (start_idx >= limit) {
+ // End of table
+ break;
+ }
+
+ int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
+ buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, processed, removed);
+ }
+}
+
+void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) {
+ const int limit = the_table()->table_size();
+
+ assert(0 <= start_idx && start_idx <= limit,
+ err_msg("start_idx (%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<oop, mtSymbol>* entry = the_table()->bucket(i);
+ while (entry != NULL) {
+ assert(!entry->is_shared(), "CDS not used for the StringTable");
+
+ f->do_oop((oop*)entry->literal_addr());
+
+ entry = entry->next();
+ }
+ }
+}
+
+void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed) {
+ const int limit = the_table()->table_size();
+
+ assert(0 <= start_idx && start_idx <= limit,
+ err_msg("start_idx (%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<oop, mtSymbol>** p = the_table()->bucket_addr(i);
+ HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
+ while (entry != NULL) {
+ assert(!entry->is_shared(), "CDS not used for the StringTable");
+
+ if (is_alive->do_object_b(entry->literal())) {
+ if (f != NULL) {
+ f->do_oop((oop*)entry->literal_addr());
+ }
+ p = entry->next_addr();
+ } else {
+ *p = entry->next();
+ the_table()->free_entry(entry);
+ (*removed)++;
+ }
+ (*processed)++;
+ entry = *p;
+ }
+ }
+}
+
+void StringTable::oops_do(OopClosure* f) {
+ buckets_oops_do(f, 0, the_table()->table_size());
+}
+
+void StringTable::possibly_parallel_oops_do(OopClosure* f) {
+ const int limit = the_table()->table_size();
+
+ for (;;) {
+ // Grab next set of buckets to scan
+ int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
+ if (start_idx >= limit) {
+ // End of table
+ break;
+ }
+
+ int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
+ buckets_oops_do(f, start_idx, end_idx);
+ }
+}
+
+// This verification is part of Universe::verify() and needs to be quick.
+// See StringTable::verify_and_compare() below for exhaustive verification.
+void StringTable::verify() {
+ for (int i = 0; i < the_table()->table_size(); ++i) {
+ HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
+ for ( ; p != NULL; p = p->next()) {
+ oop s = p->literal();
+ guarantee(s != NULL, "interned string is NULL");
+ unsigned int h = java_lang_String::hash_string(s);
+ guarantee(p->hash() == h, "broken hash in string table entry");
+ guarantee(the_table()->hash_to_index(h) == i,
+ "wrong index in string table");
+ }
+ }
+}
+
+void StringTable::dump(outputStream* st) {
+ the_table()->dump_table(st, "StringTable");
+}
+
+StringTable::VerifyRetTypes StringTable::compare_entries(
+ int bkt1, int e_cnt1,
+ HashtableEntry<oop, mtSymbol>* e_ptr1,
+ int bkt2, int e_cnt2,
+ HashtableEntry<oop, mtSymbol>* e_ptr2) {
+ // These entries are sanity checked by verify_and_compare_entries()
+ // before this function is called.
+ oop str1 = e_ptr1->literal();
+ oop str2 = e_ptr2->literal();
+
+ if (str1 == str2) {
+ tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") "
+ "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]",
+ (void *)str1, bkt1, e_cnt1, bkt2, e_cnt2);
+ return _verify_fail_continue;
+ }
+
+ if (java_lang_String::equals(str1, str2)) {
+ tty->print_cr("ERROR: identical String values in entry @ "
+ "bucket[%d][%d] and entry @ bucket[%d][%d]",
+ bkt1, e_cnt1, bkt2, e_cnt2);
+ return _verify_fail_continue;
+ }
+
+ return _verify_pass;
+}
+
+StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt,
+ HashtableEntry<oop, mtSymbol>* e_ptr,
+ StringTable::VerifyMesgModes mesg_mode) {
+
+ VerifyRetTypes ret = _verify_pass; // be optimistic
+
+ oop str = e_ptr->literal();
+ if (str == NULL) {
+ if (mesg_mode == _verify_with_mesgs) {
+ tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt,
+ e_cnt);
+ }
+ // NULL oop means no more verifications are possible
+ return _verify_fail_done;
+ }
+
+ if (str->klass() != SystemDictionary::String_klass()) {
+ if (mesg_mode == _verify_with_mesgs) {
+ tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]",
+ bkt, e_cnt);
+ }
+ // not a String means no more verifications are possible
+ return _verify_fail_done;
+ }
+
+ unsigned int h = java_lang_String::hash_string(str);
+ if (e_ptr->hash() != h) {
+ if (mesg_mode == _verify_with_mesgs) {
+ tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], "
+ "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h);
+ }
+ ret = _verify_fail_continue;
+ }
+
+ if (the_table()->hash_to_index(h) != bkt) {
+ if (mesg_mode == _verify_with_mesgs) {
+ tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], "
+ "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h,
+ the_table()->hash_to_index(h));
+ }
+ ret = _verify_fail_continue;
+ }
+
+ return ret;
+}
+
+// See StringTable::verify() above for the quick verification that is
+// part of Universe::verify(). This verification is exhaustive and
+// reports on every issue that is found. StringTable::verify() only
+// reports on the first issue that is found.
+//
+// StringTable::verify_entry() checks:
+// - oop value != NULL (same as verify())
+// - oop value is a String
+// - hash(String) == hash in entry (same as verify())
+// - index for hash == index of entry (same as verify())
+//
+// StringTable::compare_entries() checks:
+// - oops are unique across all entries
+// - String values are unique across all entries
+//
+int StringTable::verify_and_compare_entries() {
+ assert(StringTable_lock->is_locked(), "sanity check");
+
+ int fail_cnt = 0;
+
+ // first, verify all the entries individually:
+ for (int bkt = 0; bkt < the_table()->table_size(); bkt++) {
+ HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt);
+ for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) {
+ VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs);
+ if (ret != _verify_pass) {
+ fail_cnt++;
+ }
+ }
+ }
+
+ // Optimization: if the above check did not find any failures, then
+ // the comparison loop below does not need to call verify_entry()
+ // before calling compare_entries(). If there were failures, then we
+ // have to call verify_entry() to see if the entry can be passed to
+ // compare_entries() safely. When we call verify_entry() in the loop
+ // below, we do so quietly to void duplicate messages and we don't
+ // increment fail_cnt because the failures have already been counted.
+ bool need_entry_verify = (fail_cnt != 0);
+
+ // second, verify all entries relative to each other:
+ for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) {
+ HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1);
+ for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) {
+ if (need_entry_verify) {
+ VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1,
+ _verify_quietly);
+ if (ret == _verify_fail_done) {
+ // cannot use the current entry to compare against other entries
+ continue;
+ }
+ }
+
+ for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) {
+ HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2);
+ int e_cnt2;
+ for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) {
+ if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) {
+ // skip the entries up to and including the one that
+ // we're comparing against
+ continue;
+ }
+
+ if (need_entry_verify) {
+ VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2,
+ _verify_quietly);
+ if (ret == _verify_fail_done) {
+ // cannot compare against this entry
+ continue;
+ }
+ }
+
+ // compare two entries, report and count any failures:
+ if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2)
+ != _verify_pass) {
+ fail_cnt++;
+ }
+ }
+ }
+ }
+ }
+ return fail_cnt;
+}
+
+// Create a new table and using alternate hash code, populate the new table
+// with the existing strings. Set flag to use the alternate hash code afterwards.
+void StringTable::rehash_table() {
+ assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+ // This should never happen with -Xshare:dump but it might in testing mode.
+ if (DumpSharedSpaces) return;
+ StringTable* new_table = new StringTable();
+
+ // Rehash the table
+ the_table()->move_to(new_table);
+
+ // Delete the table and buckets (entries are reused in new table).
+ delete _the_table;
+ // Don't check if we need rehashing until the table gets unbalanced again.
+ // Then rehash with a new global seed.
+ _needs_rehashing = false;
+ _the_table = new_table;
+}