Sat, 01 Sep 2012 13:25:18 -0400
6964458: Reimplement class meta-data storage to use native memory
Summary: Remove PermGen, allocate meta-data in metaspace linked to class loaders, rewrite GC walking, rewrite and rename metadata to be C++ classes
Reviewed-by: jmasa, stefank, never, coleenp, kvn, brutisso, mgerdin, dholmes, jrose, twisti, roland
Contributed-by: jmasa <jon.masamitsu@oracle.com>, stefank <stefan.karlsson@oracle.com>, mgerdin <mikael.gerdin@oracle.com>, never <tom.rodriguez@oracle.com>
1 /*
2 * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
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23 */
25 #include "precompiled.hpp"
26 #include "classfile/placeholders.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "oops/oop.inline.hpp"
29 #include "runtime/fieldType.hpp"
30 #include "utilities/hashtable.inline.hpp"
32 // Placeholder methods
34 PlaceholderEntry* PlaceholderTable::new_entry(int hash, Symbol* name,
35 ClassLoaderData* loader_data,
36 bool havesupername,
37 Symbol* supername) {
38 PlaceholderEntry* entry = (PlaceholderEntry*)Hashtable<Symbol*, mtClass>::new_entry(hash, name);
39 // Hashtable with Symbol* literal must increment and decrement refcount.
40 name->increment_refcount();
41 entry->set_loader_data(loader_data);
42 entry->set_havesupername(havesupername);
43 entry->set_supername(supername);
44 entry->set_superThreadQ(NULL);
45 entry->set_loadInstanceThreadQ(NULL);
46 entry->set_defineThreadQ(NULL);
47 entry->set_definer(NULL);
48 entry->set_instanceKlass(NULL);
49 return entry;
50 }
52 void PlaceholderTable::free_entry(PlaceholderEntry* entry) {
53 // decrement Symbol refcount here because Hashtable doesn't.
54 entry->literal()->decrement_refcount();
55 if (entry->supername() != NULL) entry->supername()->decrement_refcount();
56 Hashtable<Symbol*, mtClass>::free_entry(entry);
57 }
60 // Placeholder objects represent classes currently being loaded.
61 // All threads examining the placeholder table must hold the
62 // SystemDictionary_lock, so we don't need special precautions
63 // on store ordering here.
64 void PlaceholderTable::add_entry(int index, unsigned int hash,
65 Symbol* class_name, ClassLoaderData* loader_data,
66 bool havesupername, Symbol* supername){
67 assert_locked_or_safepoint(SystemDictionary_lock);
68 assert(class_name != NULL, "adding NULL obj");
70 // Both readers and writers are locked so it's safe to just
71 // create the placeholder and insert it in the list without a membar.
72 PlaceholderEntry* entry = new_entry(hash, class_name, loader_data, havesupername, supername);
73 add_entry(index, entry);
74 }
77 // Remove a placeholder object.
78 void PlaceholderTable::remove_entry(int index, unsigned int hash,
79 Symbol* class_name,
80 ClassLoaderData* loader_data) {
81 assert_locked_or_safepoint(SystemDictionary_lock);
82 PlaceholderEntry** p = bucket_addr(index);
83 while (*p) {
84 PlaceholderEntry *probe = *p;
85 if (probe->hash() == hash && probe->equals(class_name, loader_data)) {
86 // Delete entry
87 *p = probe->next();
88 free_entry(probe);
89 return;
90 }
91 p = probe->next_addr();
92 }
93 }
95 PlaceholderEntry* PlaceholderTable::get_entry(int index, unsigned int hash,
96 Symbol* class_name,
97 ClassLoaderData* loader_data) {
98 assert_locked_or_safepoint(SystemDictionary_lock);
100 for (PlaceholderEntry *place_probe = bucket(index);
101 place_probe != NULL;
102 place_probe = place_probe->next()) {
103 if (place_probe->hash() == hash &&
104 place_probe->equals(class_name, loader_data)) {
105 return place_probe;
106 }
107 }
108 return NULL;
109 }
111 Symbol* PlaceholderTable::find_entry(int index, unsigned int hash,
112 Symbol* class_name,
113 ClassLoaderData* loader_data) {
114 PlaceholderEntry* probe = get_entry(index, hash, class_name, loader_data);
115 return (probe? probe->klassname(): (Symbol*)NULL);
116 }
118 // find_and_add returns probe pointer - old or new
119 // If no entry exists, add a placeholder entry
120 // If entry exists, reuse entry
121 // For both, push SeenThread for classloadAction
122 // if havesupername: this is used for circularity for instanceklass loading
123 PlaceholderEntry* PlaceholderTable::find_and_add(int index, unsigned int hash,
124 Symbol* name,
125 ClassLoaderData* loader_data,
126 classloadAction action,
127 Symbol* supername,
128 Thread* thread) {
129 PlaceholderEntry* probe = get_entry(index, hash, name, loader_data);
130 if (probe == NULL) {
131 // Nothing found, add place holder
132 add_entry(index, hash, name, loader_data, (action == LOAD_SUPER), supername);
133 probe = get_entry(index, hash, name, loader_data);
134 } else {
135 if (action == LOAD_SUPER) {
136 probe->set_havesupername(true);
137 probe->set_supername(supername);
138 }
139 }
140 if (probe) probe->add_seen_thread(thread, action);
141 return probe;
142 }
145 // placeholder used to track class loading internal states
146 // placeholder existence now for loading superclass/superinterface
147 // superthreadQ tracks class circularity, while loading superclass/superinterface
148 // loadInstanceThreadQ tracks load_instance_class calls
149 // definer() tracks the single thread that owns define token
150 // defineThreadQ tracks waiters on defining thread's results
151 // 1st claimant creates placeholder
152 // find_and_add adds SeenThread entry for appropriate queue
153 // All claimants remove SeenThread after completing action
154 // On removal: if definer and all queues empty, remove entry
155 // Note: you can be in both placeholders and systemDictionary
156 // see parse_stream for redefine classes
157 // Therefore - must always check SD first
158 // Ignores the case where entry is not found
159 void PlaceholderTable::find_and_remove(int index, unsigned int hash,
160 Symbol* name, ClassLoaderData* loader_data, Thread* thread) {
161 assert_locked_or_safepoint(SystemDictionary_lock);
162 PlaceholderEntry *probe = get_entry(index, hash, name, loader_data);
163 if (probe != NULL) {
164 // No other threads using this entry
165 if ((probe->superThreadQ() == NULL) && (probe->loadInstanceThreadQ() == NULL)
166 && (probe->defineThreadQ() == NULL) && (probe->definer() == NULL)) {
167 remove_entry(index, hash, name, loader_data);
168 }
169 }
170 }
172 PlaceholderTable::PlaceholderTable(int table_size)
173 : TwoOopHashtable<Symbol*, mtClass>(table_size, sizeof(PlaceholderEntry)) {
174 }
177 void PlaceholderTable::classes_do(KlassClosure* f) {
178 for (int index = 0; index < table_size(); index++) {
179 for (PlaceholderEntry* probe = bucket(index);
180 probe != NULL;
181 probe = probe->next()) {
182 probe->classes_do(f);
183 }
184 }
185 }
188 void PlaceholderEntry::classes_do(KlassClosure* closure) {
189 assert(klassname() != NULL, "should have a non-null klass");
190 if (_instanceKlass != NULL) {
191 closure->do_klass(InstanceKlass());
192 }
193 }
195 // do all entries in the placeholder table
196 void PlaceholderTable::entries_do(void f(Symbol*)) {
197 for (int index = 0; index < table_size(); index++) {
198 for (PlaceholderEntry* probe = bucket(index);
199 probe != NULL;
200 probe = probe->next()) {
201 f(probe->klassname());
202 }
203 }
204 }
207 #ifndef PRODUCT
208 // Note, doesn't append a cr
209 void PlaceholderEntry::print() const {
210 klassname()->print_value();
211 if (loader_data() != NULL) {
212 tty->print(", loader ");
213 loader_data()->print_value();
214 }
215 if (supername() != NULL) {
216 tty->print(", supername ");
217 supername()->print_value();
218 }
219 if (definer() != NULL) {
220 tty->print(", definer ");
221 definer()->print_value();
222 }
223 if (InstanceKlass() != NULL) {
224 tty->print(", InstanceKlass ");
225 InstanceKlass()->print_value();
226 }
227 tty->print("\n");
228 tty->print("loadInstanceThreadQ threads:");
229 loadInstanceThreadQ()->printActionQ();
230 tty->print("\n");
231 tty->print("superThreadQ threads:");
232 superThreadQ()->printActionQ();
233 tty->print("\n");
234 tty->print("defineThreadQ threads:");
235 defineThreadQ()->printActionQ();
236 tty->print("\n");
237 }
238 #endif
240 void PlaceholderEntry::verify() const {
241 guarantee(loader_data() != NULL, "Must have been setup.");
242 guarantee(loader_data()->class_loader() == NULL || loader_data()->class_loader()->is_instance(),
243 "checking type of _loader");
244 guarantee(InstanceKlass() == NULL
245 || Klass::cast(InstanceKlass())->oop_is_instance(),
246 "checking type of InstanceKlass result");
247 }
249 void PlaceholderTable::verify() {
250 int element_count = 0;
251 for (int pindex = 0; pindex < table_size(); pindex++) {
252 for (PlaceholderEntry* probe = bucket(pindex);
253 probe != NULL;
254 probe = probe->next()) {
255 probe->verify();
256 element_count++; // both klasses and place holders count
257 }
258 }
259 guarantee(number_of_entries() == element_count,
260 "Verify of system dictionary failed");
261 }
264 #ifndef PRODUCT
265 void PlaceholderTable::print() {
266 for (int pindex = 0; pindex < table_size(); pindex++) {
267 for (PlaceholderEntry* probe = bucket(pindex);
268 probe != NULL;
269 probe = probe->next()) {
270 if (Verbose) tty->print("%4d: ", pindex);
271 tty->print(" place holder ");
273 probe->print();
274 tty->cr();
275 }
276 }
277 }
278 #endif