1 /*
2 * Copyright (c) 2001, 2024, 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
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7 * published by the Free Software Foundation.
8 *
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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
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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 #include "oops/oopsHierarchy.hpp"
32
33 class Thread;
34 class Monitor;
35 class SATBMarkQueueSet;
36
37 // Base class for processing the contents of a SATB buffer.
38 class SATBBufferClosure : public StackObj {
39 protected:
40 ~SATBBufferClosure() { }
41
42 public:
43 // Process the SATB entries in the designated buffer range.
44 virtual void do_buffer(void** buffer, size_t size) = 0;
45 };
46
47 // A PtrQueue whose elements are (possibly stale) pointers to object heads.
48 class SATBMarkQueue: public PtrQueue {
49 friend class VMStructs;
50 friend class SATBMarkQueueSet;
51
52 private:
53 // Per-queue (so thread-local) cache of the SATBMarkQueueSet's
54 // active state, to support inline barriers in compiled code.
55 bool _active;
56
57 public:
58 SATBMarkQueue(SATBMarkQueueSet* qset);
59
60 bool is_active() const { return _active; }
61 void set_active(bool value) { _active = value; }
62
63 #ifndef PRODUCT
64 // Helpful for debugging
65 void print(const char* name);
66 #endif // PRODUCT
67
68 // Compiler support.
69 static ByteSize byte_offset_of_index() {
70 return PtrQueue::byte_offset_of_index<SATBMarkQueue>();
71 }
72 using PtrQueue::byte_width_of_index;
73
74 static ByteSize byte_offset_of_buf() {
75 return PtrQueue::byte_offset_of_buf<SATBMarkQueue>();
76 }
77 using PtrQueue::byte_width_of_buf;
78
79 static ByteSize byte_offset_of_active() {
80 return byte_offset_of(SATBMarkQueue, _active);
81 }
82
83 static ByteSize byte_width_of_active() { return in_ByteSize(sizeof(bool)); }
84 };
85
86 class SATBMarkQueueSet: public PtrQueueSet {
87
88 DEFINE_PAD_MINUS_SIZE(1, DEFAULT_PADDING_SIZE, 0);
89 PaddedEnd<BufferNode::Stack> _list;
90 volatile size_t _count_and_process_flag;
91 // These are rarely (if ever) changed, so same cache line as count.
92 size_t _process_completed_buffers_threshold;
93 size_t _buffer_enqueue_threshold;
94 // SATB is only active during marking. Enqueuing is only done when active.
95 bool _all_active;
96 DEFINE_PAD_MINUS_SIZE(2, DEFAULT_PADDING_SIZE, 4 * sizeof(size_t));
97
98 BufferNode* get_completed_buffer();
99 void abandon_completed_buffers();
100
101 #ifdef ASSERT
102 void dump_active_states(bool expected_active);
103 void verify_active_states(bool expected_active);
104 #endif // ASSERT
105
106 protected:
107 SATBMarkQueueSet(BufferNode::Allocator* allocator);
108 ~SATBMarkQueueSet();
109
110 void handle_zero_index(SATBMarkQueue& queue);
111
112 // Return true if the queue's buffer should be enqueued, even if not full.
113 // The default method uses the buffer enqueue threshold.
114 bool should_enqueue_buffer(SATBMarkQueue& queue);
115
116 template<typename Filter>
117 void apply_filter(Filter filter, SATBMarkQueue& queue);
118
119 public:
120 virtual SATBMarkQueue& satb_queue_for_thread(Thread* const t) const = 0;
121
122 bool is_active() const { return _all_active; }
123
124 // Apply "set_active(active)" to all SATB queues in the set. It should be
125 // called only with the world stopped. The method will assert that the
126 // SATB queues of all threads it visits, as well as the SATB queue
127 // set itself, has an active value same as expected_active.
128 void set_active_all_threads(bool active, bool expected_active);
129
130 void set_process_completed_buffers_threshold(size_t value);
131
132 size_t buffer_enqueue_threshold() const { return _buffer_enqueue_threshold; }
133 void set_buffer_enqueue_threshold_percentage(uint value);
134
135 // If there exists some completed buffer, pop and process it, and
136 // return true. Otherwise return false. Processing a buffer
137 // consists of applying the closure to the active range of the
138 // buffer; the leading entries may be excluded due to filtering.
139 bool apply_closure_to_completed_buffer(SATBBufferClosure* cl);
140
141 void flush_queue(SATBMarkQueue& queue);
142
143 // Add obj to queue. This qset and the queue must be active.
144 void enqueue_known_active(SATBMarkQueue& queue, oop obj);
145 virtual void filter(SATBMarkQueue& queue) = 0;
146 virtual void enqueue_completed_buffer(BufferNode* node);
147
148 // The number of buffers in the list. Racy and not updated atomically
149 // with the set of completed buffers.
150 size_t completed_buffers_num() const {
151 return _count_and_process_flag >> 1;
152 }
153
154 // Return true if completed buffers should be processed.
155 bool process_completed_buffers() const {
156 return (_count_and_process_flag & 1) != 0;
157 }
158
159 #ifndef PRODUCT
160 // Helpful for debugging
161 void print_all(const char* msg);
162 #endif // PRODUCT
163
164 // If a marking is being abandoned, reset any unprocessed log buffers.
165 void abandon_partial_marking();
166 };
167
168 // Removes entries from queue's buffer that are no longer needed, as
169 // determined by filter. If e is a void* entry in queue's buffer,
170 // filter_out(e) must be a valid expression whose value is convertible
171 // to bool. Entries are removed (filtered out) if the result is true,
172 // retained if false.
173 template<typename Filter>
174 inline void SATBMarkQueueSet::apply_filter(Filter filter_out, SATBMarkQueue& queue) {
175 void** buf = queue.buffer();
176
177 if (buf == nullptr) {
178 // Nothing to do, and avoid pointer arithmetic on nullptr below.
179 return;
180 }
181
182 // Two-fingered compaction toward the end.
183 void** src = buf + queue.index();
184 void** dst = buf + queue.current_capacity();
185 assert(src <= dst, "invariant");
186 for ( ; src < dst; ++src) {
187 // Search low to high for an entry to keep.
188 void* entry = *src;
189 if (!filter_out(entry)) {
190 // Found keeper. Search high to low for an entry to discard.
191 while (src < --dst) {
192 if (filter_out(*dst)) {
193 *dst = entry; // Replace discard with keeper.
194 break;
195 }
196 }
197 // If discard search failed (src == dst), the outer loop will also end.
198 }
199 }
200 // dst points to the lowest retained entry, or the end of the buffer
201 // if all the entries were filtered out.
202 queue.set_index(dst - buf);
203 }
204
205 #endif // SHARE_GC_SHARED_SATBMARKQUEUE_HPP