1 /*
2 * Copyright (c) 2001, 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_BUFFERINGOOPCLOSURE_HPP
26 #define SHARE_VM_GC_G1_BUFFERINGOOPCLOSURE_HPP
27
28 #include "memory/iterator.hpp"
29 #include "oops/oopsHierarchy.hpp"
30 #include "runtime/os.hpp"
31 #include "utilities/debug.hpp"
32
33 // A BufferingOops closure tries to separate out the cost of finding roots
34 // from the cost of applying closures to them. It maintains an array of
35 // ref-containing locations. Until the array is full, applying the closure
36 // to an oop* merely records that location in the array. Since this
37 // closure app cost is small, an elapsed timer can approximately attribute
38 // all of this cost to the cost of finding the roots. When the array fills
39 // up, the wrapped closure is applied to all elements, keeping track of
40 // this elapsed time of this process, and leaving the array empty.
41 // The caller must be sure to call "done" to process any unprocessed
42 // buffered entries.
43
44 class BufferingOopClosure: public OopClosure {
45 friend class BufferingOopClosureTest;
46 protected:
47 static const size_t BufferLength = 1024;
48
49 // We need to know if the buffered addresses contain oops or narrowOops.
50 // We can't tag the addresses the way StarTask does, because we need to
51 // be able to handle unaligned addresses coming from oops embedded in code.
52 //
53 // The addresses for the full-sized oops are filled in from the bottom,
54 // while the addresses for the narrowOops are filled in from the top.
55 OopOrNarrowOopStar _buffer[BufferLength];
56 OopOrNarrowOopStar* _oop_top;
57 OopOrNarrowOopStar* _narrowOop_bottom;
58
59 OopClosure* _oc;
60 double _closure_app_seconds;
61
62
63 bool is_buffer_empty() {
64 return _oop_top == _buffer && _narrowOop_bottom == (_buffer + BufferLength - 1);
65 }
66
67 bool is_buffer_full() {
68 return _narrowOop_bottom < _oop_top;
69 }
70
71 // Process addresses containing full-sized oops.
72 void process_oops() {
73 for (OopOrNarrowOopStar* curr = _buffer; curr < _oop_top; ++curr) {
74 _oc->do_oop((oop*)(*curr));
75 }
76 _oop_top = _buffer;
77 }
78
79 // Process addresses containing narrow oops.
80 void process_narrowOops() {
81 for (OopOrNarrowOopStar* curr = _buffer + BufferLength - 1; curr > _narrowOop_bottom; --curr) {
82 _oc->do_oop((narrowOop*)(*curr));
83 }
84 _narrowOop_bottom = _buffer + BufferLength - 1;
85 }
86
87 // Apply the closure to all oops and clear the buffer.
88 // Accumulate the time it took.
89 void process_buffer() {
90 double start = os::elapsedTime();
91
92 process_oops();
93 process_narrowOops();
94
95 _closure_app_seconds += (os::elapsedTime() - start);
96 }
97
98 void process_buffer_if_full() {
99 if (is_buffer_full()) {
100 process_buffer();
101 }
102 }
103
104 void add_narrowOop(narrowOop* p) {
105 assert(!is_buffer_full(), "Buffer should not be full");
106 *_narrowOop_bottom = (OopOrNarrowOopStar)p;
107 _narrowOop_bottom--;
108 }
109
110 void add_oop(oop* p) {
111 assert(!is_buffer_full(), "Buffer should not be full");
112 *_oop_top = (OopOrNarrowOopStar)p;
113 _oop_top++;
114 }
115
116 public:
117 virtual void do_oop(narrowOop* p) {
118 process_buffer_if_full();
119 add_narrowOop(p);
120 }
121
122 virtual void do_oop(oop* p) {
123 process_buffer_if_full();
124 add_oop(p);
125 }
126
127 void done() {
128 if (!is_buffer_empty()) {
129 process_buffer();
130 }
131 }
132
133 double closure_app_seconds() {
134 return _closure_app_seconds;
135 }
136
137 BufferingOopClosure(OopClosure *oc) :
138 _oc(oc),
139 _oop_top(_buffer),
140 _narrowOop_bottom(_buffer + BufferLength - 1),
141 _closure_app_seconds(0.0) { }
142 };
143
144 #endif // SHARE_VM_GC_G1_BUFFERINGOOPCLOSURE_HPP