1 /*
2 * Copyright (c) 2014, 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.
18 *
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
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1STRINGDEDUP_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1STRINGDEDUP_HPP
27
28 //
29 // String Deduplication
30 //
31 // String deduplication aims to reduce the heap live-set by deduplicating identical
32 // instances of String so that they share the same backing character array.
33 //
34 // The deduplication process is divided in two main parts, 1) finding the objects to
35 // deduplicate, and 2) deduplicating those objects. The first part is done as part of
36 // a normal GC cycle when objects are marked or evacuated. At this time a check is
37 // applied on each object to check if it is a candidate for deduplication. If so, the
38 // object is placed on the deduplication queue for later processing. The second part,
39 // processing the objects on the deduplication queue, is a concurrent phase which
40 // starts right after the stop-the-wold marking/evacuation phase. This phase is
41 // executed by the deduplication thread, which pulls deduplication candidates of the
42 // deduplication queue and tries to deduplicate them.
43 //
44 // A deduplication hashtable is used to keep track of all unique character arrays
45 // used by String objects. When deduplicating, a lookup is made in this table to see
46 // if there is already an identical character array somewhere on the heap. If so, the
184 size_t claim_table_partition(size_t partition_size);
185
186 // Applies and returns the result from the is_alive closure, or
187 // returns true if no such closure was provided.
188 bool is_alive(oop o) {
189 if (_is_alive != NULL) {
190 return _is_alive->do_object_b(o);
191 }
192 return true;
193 }
194
195 // Applies the keep_alive closure, or does nothing if no such
196 // closure was provided.
197 void keep_alive(oop* p) {
198 if (_keep_alive != NULL) {
199 _keep_alive->do_oop(p);
200 }
201 }
202 };
203
204 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1STRINGDEDUP_HPP
|
1 /*
2 * Copyright (c) 2014, 2015, 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.
18 *
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
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_G1_G1STRINGDEDUP_HPP
26 #define SHARE_VM_GC_G1_G1STRINGDEDUP_HPP
27
28 //
29 // String Deduplication
30 //
31 // String deduplication aims to reduce the heap live-set by deduplicating identical
32 // instances of String so that they share the same backing character array.
33 //
34 // The deduplication process is divided in two main parts, 1) finding the objects to
35 // deduplicate, and 2) deduplicating those objects. The first part is done as part of
36 // a normal GC cycle when objects are marked or evacuated. At this time a check is
37 // applied on each object to check if it is a candidate for deduplication. If so, the
38 // object is placed on the deduplication queue for later processing. The second part,
39 // processing the objects on the deduplication queue, is a concurrent phase which
40 // starts right after the stop-the-wold marking/evacuation phase. This phase is
41 // executed by the deduplication thread, which pulls deduplication candidates of the
42 // deduplication queue and tries to deduplicate them.
43 //
44 // A deduplication hashtable is used to keep track of all unique character arrays
45 // used by String objects. When deduplicating, a lookup is made in this table to see
46 // if there is already an identical character array somewhere on the heap. If so, the
184 size_t claim_table_partition(size_t partition_size);
185
186 // Applies and returns the result from the is_alive closure, or
187 // returns true if no such closure was provided.
188 bool is_alive(oop o) {
189 if (_is_alive != NULL) {
190 return _is_alive->do_object_b(o);
191 }
192 return true;
193 }
194
195 // Applies the keep_alive closure, or does nothing if no such
196 // closure was provided.
197 void keep_alive(oop* p) {
198 if (_keep_alive != NULL) {
199 _keep_alive->do_oop(p);
200 }
201 }
202 };
203
204 #endif // SHARE_VM_GC_G1_G1STRINGDEDUP_HPP
|