1 /*
2 * Copyright (c) 2001, 2019, 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.
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23 */
24
25 #ifndef SHARE_GC_SHARED_SATBMARKQUEUE_HPP
26 #define SHARE_GC_SHARED_SATBMARKQUEUE_HPP
27
28 #include "gc/shared/ptrQueue.hpp"
29 #include "memory/allocation.hpp"
30 #include "memory/padded.hpp"
31
32 class Thread;
33 class Monitor;
34 class SATBMarkQueueSet;
35
36 // Base class for processing the contents of a SATB buffer.
37 class SATBBufferClosure : public StackObj {
38 protected:
39 ~SATBBufferClosure() { }
40
41 public:
42 // Process the SATB entries in the designated buffer range.
43 virtual void do_buffer(void** buffer, size_t size) = 0;
44 };
45
46 // A PtrQueue whose elements are (possibly stale) pointers to object heads.
47 class SATBMarkQueue: public PtrQueue {
48 friend class SATBMarkQueueSet;
49
50 private:
51 // Filter out unwanted entries from the buffer.
52 inline void filter();
53
54 // Removes entries from the buffer that are no longer needed.
55 template<typename Filter>
56 inline void apply_filter(Filter filter_out);
57
58 protected:
59 virtual void handle_completed_buffer();
60
61 public:
62 SATBMarkQueue(SATBMarkQueueSet* qset);
63
64 // Process queue entries and free resources.
65 void flush();
66
67 inline SATBMarkQueueSet* satb_qset() const;
68
69 // Apply cl to the active part of the buffer.
70 // Prerequisite: Must be at a safepoint.
71 void apply_closure_and_empty(SATBBufferClosure* cl);
72
73 #ifndef PRODUCT
74 // Helpful for debugging
75 void print(const char* name);
76 #endif // PRODUCT
77
78 // Compiler support.
79 static ByteSize byte_offset_of_index() {
80 return PtrQueue::byte_offset_of_index<SATBMarkQueue>();
81 }
82 using PtrQueue::byte_width_of_index;
83
84 static ByteSize byte_offset_of_buf() {
85 return PtrQueue::byte_offset_of_buf<SATBMarkQueue>();
86 }
87 using PtrQueue::byte_width_of_buf;
88
89 static ByteSize byte_offset_of_active() {
90 return PtrQueue::byte_offset_of_active<SATBMarkQueue>();
91 }
92 using PtrQueue::byte_width_of_active;
93
94 };
95
96 class SATBMarkQueueSet: public PtrQueueSet {
97
98 DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, 0);
99 PaddedEnd<BufferNode::Stack> _list;
100 volatile size_t _count_and_process_flag;
101 // These are rarely (if ever) changed, so same cache line as count.
102 size_t _process_completed_buffers_threshold;
103 size_t _buffer_enqueue_threshold;
104 DEFINE_PAD_MINUS_SIZE(2, DEFAULT_CACHE_LINE_SIZE, 3 * sizeof(size_t));
105
106 BufferNode* get_completed_buffer();
107 void abandon_completed_buffers();
108
109 #ifdef ASSERT
110 void dump_active_states(bool expected_active);
111 void verify_active_states(bool expected_active);
112 #endif // ASSERT
113
114 protected:
115 SATBMarkQueueSet(BufferNode::Allocator* allocator);
116 ~SATBMarkQueueSet();
117
118 template<typename Filter>
119 void apply_filter(Filter filter, SATBMarkQueue* queue) {
120 queue->apply_filter(filter);
121 }
122
123 public:
124 virtual SATBMarkQueue& satb_queue_for_thread(Thread* const t) const = 0;
125
126 // Apply "set_active(active)" to all SATB queues in the set. It should be
127 // called only with the world stopped. The method will assert that the
128 // SATB queues of all threads it visits, as well as the SATB queue
129 // set itself, has an active value same as expected_active.
130 void set_active_all_threads(bool active, bool expected_active);
131
132 void set_process_completed_buffers_threshold(size_t value);
133
134 size_t buffer_enqueue_threshold() const { return _buffer_enqueue_threshold; }
135 void set_buffer_enqueue_threshold_percentage(uint value);
136
137 virtual void filter(SATBMarkQueue* queue) = 0;
138
139 // If there exists some completed buffer, pop and process it, and
140 // return true. Otherwise return false. Processing a buffer
141 // consists of applying the closure to the active range of the
142 // buffer; the leading entries may be excluded due to filtering.
143 bool apply_closure_to_completed_buffer(SATBBufferClosure* cl);
144
145 virtual void enqueue_completed_buffer(BufferNode* node);
146
147 // The number of buffers in the list. Racy and not updated atomically
148 // with the set of completed buffers.
149 size_t completed_buffers_num() const {
150 return _count_and_process_flag >> 1;
151 }
152
153 // Return true if completed buffers should be processed.
154 bool process_completed_buffers() const {
155 return (_count_and_process_flag & 1) != 0;
156 }
157
158 #ifndef PRODUCT
159 // Helpful for debugging
160 void print_all(const char* msg);
161 #endif // PRODUCT
162
163 // If a marking is being abandoned, reset any unprocessed log buffers.
164 void abandon_partial_marking();
165 };
166
167 inline SATBMarkQueueSet* SATBMarkQueue::satb_qset() const {
168 return static_cast<SATBMarkQueueSet*>(qset());
169 }
170
171 inline void SATBMarkQueue::filter() {
172 satb_qset()->filter(this);
173 }
174
175 // Removes entries from the buffer that are no longer needed, as
176 // determined by filter. If e is a void* entry in the buffer,
177 // filter_out(e) must be a valid expression whose value is convertible
178 // to bool. Entries are removed (filtered out) if the result is true,
179 // retained if false.
180 template<typename Filter>
181 inline void SATBMarkQueue::apply_filter(Filter filter_out) {
182 void** buf = this->_buf;
183
184 if (buf == NULL) {
185 // nothing to do
186 return;
187 }
188
189 // Two-fingered compaction toward the end.
190 void** src = &buf[this->index()];
191 void** dst = &buf[this->capacity()];
192 assert(src <= dst, "invariant");
193 for ( ; src < dst; ++src) {
194 // Search low to high for an entry to keep.
195 void* entry = *src;
196 if (!filter_out(entry)) {
197 // Found keeper. Search high to low for an entry to discard.
198 while (src < --dst) {
199 if (filter_out(*dst)) {
200 *dst = entry; // Replace discard with keeper.
201 break;
202 }
203 }
204 // If discard search failed (src == dst), the outer loop will also end.
205 }
206 }
207 // dst points to the lowest retained entry, or the end of the buffer
208 // if all the entries were filtered out.
209 this->set_index(dst - buf);
210 }
211
212 #endif // SHARE_GC_SHARED_SATBMARKQUEUE_HPP