1 /*
2 * Copyright (c) 2001, 2018, 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 #include "precompiled.hpp"
26 #include "jvm.h"
27 #include "gc/shared/satbMarkQueue.hpp"
28 #include "gc/shared/collectedHeap.hpp"
29 #include "logging/log.hpp"
30 #include "memory/allocation.inline.hpp"
31 #include "oops/oop.inline.hpp"
32 #include "runtime/mutexLocker.hpp"
33 #include "runtime/safepoint.hpp"
34 #include "runtime/thread.hpp"
35 #include "runtime/threadSMR.hpp"
36 #include "runtime/vmThread.hpp"
37
38 SATBMarkQueue::SATBMarkQueue(SATBMarkQueueSet* qset, bool permanent) :
39 // SATB queues are only active during marking cycles. We create
40 // them with their active field set to false. If a thread is
41 // created during a cycle and its SATB queue needs to be activated
42 // before the thread starts running, we'll need to set its active
43 // field to true. This is done in G1SBarrierSet::on_thread_attach().
44 PtrQueue(qset, permanent, false /* active */)
45 { }
46
47 void SATBMarkQueue::flush() {
48 // Filter now to possibly save work later. If filtering empties the
49 // buffer then flush_impl can deallocate the buffer.
50 filter();
51 flush_impl();
52 }
53
54 // This method removes entries from a SATB buffer that will not be
55 // useful to the concurrent marking threads. Entries are retained if
56 // they require marking and are not already marked. Retained entries
57 // are compacted toward the top of the buffer.
58 void SATBMarkQueue::filter() {
59 CollectedHeap* heap = Universe::heap();
60 void** buf = _buf;
61
62 if (buf == NULL) {
63 // nothing to do
64 return;
65 }
66
67 // Two-fingered compaction toward the end.
68 void** src = &buf[index()];
69 void** dst = &buf[capacity()];
70 assert(src <= dst, "invariant");
71 for ( ; src < dst; ++src) {
72 // Search low to high for an entry to keep.
73 void* entry = *src;
74 if (heap->retain_satb_entry(entry)) {
75 // Found keeper. Search high to low for an entry to discard.
76 while (src < --dst) {
77 if (!heap->retain_satb_entry(*dst)) {
78 *dst = entry; // Replace discard with keeper.
79 break;
80 }
81 }
82 // If discard search failed (src == dst), the outer loop will also end.
83 }
84 }
85 // dst points to the lowest retained entry, or the end of the buffer
86 // if all the entries were filtered out.
87 set_index(dst - buf);
88 }
89
90 // This method will first apply the above filtering to the buffer. If
91 // post-filtering a large enough chunk of the buffer has been cleared
92 // we can re-use the buffer (instead of enqueueing it) and we can just
93 // allow the mutator to carry on executing using the same buffer
94 // instead of replacing it.
95
96 bool SATBMarkQueue::should_enqueue_buffer() {
97 assert(_lock == NULL || _lock->owned_by_self(),
98 "we should have taken the lock before calling this");
99
100 // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering.
101
102 // This method should only be called if there is a non-NULL buffer
103 // that is full.
104 assert(index() == 0, "pre-condition");
105 assert(_buf != NULL, "pre-condition");
106
107 filter();
108
109 size_t cap = capacity();
110 size_t percent_used = ((cap - index()) * 100) / cap;
111 bool should_enqueue = percent_used > G1SATBBufferEnqueueingThresholdPercent;
112 return should_enqueue;
113 }
114
115 void SATBMarkQueue::apply_closure_and_empty(SATBBufferClosure* cl) {
116 assert(SafepointSynchronize::is_at_safepoint(),
117 "SATB queues must only be processed at safepoints");
118 if (_buf != NULL) {
119 cl->do_buffer(&_buf[index()], size());
120 reset();
121 }
122 }
123
124 #ifndef PRODUCT
125 // Helpful for debugging
126
127 static void print_satb_buffer(const char* name,
128 void** buf,
129 size_t index,
130 size_t capacity) {
131 tty->print_cr(" SATB BUFFER [%s] buf: " PTR_FORMAT " index: " SIZE_FORMAT
132 " capacity: " SIZE_FORMAT,
133 name, p2i(buf), index, capacity);
134 }
135
136 void SATBMarkQueue::print(const char* name) {
137 print_satb_buffer(name, _buf, index(), capacity());
138 }
139
140 #endif // PRODUCT
141
142 SATBMarkQueueSet::SATBMarkQueueSet() :
143 PtrQueueSet(),
144 _shared_satb_queue(this, true /* permanent */) { }
145
146 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
147 int process_completed_threshold,
148 Mutex* lock) {
149 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
150 _shared_satb_queue.set_lock(lock);
151 }
152
153 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
154 Universe::heap()->satb_mark_queue(t)->handle_zero_index();
155 }
156
157 #ifdef ASSERT
158 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
159 log_error(gc, verify)("Expected SATB active state: %s", expected_active ? "ACTIVE" : "INACTIVE");
160 log_error(gc, verify)("Actual SATB active states:");
161 log_error(gc, verify)(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
162 CollectedHeap* heap = Universe::heap();
163 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
164 log_error(gc, verify)(" Thread \"%s\" queue: %s", t->name(), heap->satb_mark_queue(t)->is_active() ? "ACTIVE" : "INACTIVE");
165 }
166 log_error(gc, verify)(" Shared queue: %s", shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
167 }
168
169 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
170 // Verify queue set state
171 if (is_active() != expected_active) {
172 dump_active_states(expected_active);
173 guarantee(false, "SATB queue set has an unexpected active state");
174 }
175
176 // Verify thread queue states
177 CollectedHeap* heap = Universe::heap();
178 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
179 if (heap->satb_mark_queue(t)->is_active() != expected_active) {
180 dump_active_states(expected_active);
181 guarantee(false, "Thread SATB queue has an unexpected active state");
182 }
183 }
184
185 // Verify shared queue state
186 if (shared_satb_queue()->is_active() != expected_active) {
187 dump_active_states(expected_active);
188 guarantee(false, "Shared SATB queue has an unexpected active state");
189 }
190 }
191 #endif // ASSERT
192
193 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
194 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
195 #ifdef ASSERT
196 verify_active_states(expected_active);
197 #endif // ASSERT
198 _all_active = active;
199 CollectedHeap* heap = Universe::heap();
200 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
201 heap->satb_mark_queue(t)->set_active(active);
202 }
203 shared_satb_queue()->set_active(active);
204 }
205
206 void SATBMarkQueueSet::filter_thread_buffers() {
207 CollectedHeap* heap = Universe::heap();
208 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
209 heap->satb_mark_queue(t)->filter();
210 }
211 shared_satb_queue()->filter();
212 }
213
214 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) {
215 BufferNode* nd = NULL;
216 {
217 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
218 if (_completed_buffers_head != NULL) {
219 nd = _completed_buffers_head;
220 _completed_buffers_head = nd->next();
221 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
222 _n_completed_buffers--;
223 if (_n_completed_buffers == 0) _process_completed = false;
224 }
225 }
226 if (nd != NULL) {
227 void **buf = BufferNode::make_buffer_from_node(nd);
228 size_t index = nd->index();
229 size_t size = buffer_size();
230 assert(index <= size, "invariant");
231 cl->do_buffer(buf + index, size - index);
232 deallocate_buffer(nd);
233 return true;
234 } else {
235 return false;
236 }
237 }
238
239 #ifndef PRODUCT
240 // Helpful for debugging
241
242 #define SATB_PRINTER_BUFFER_SIZE 256
243
244 void SATBMarkQueueSet::print_all(const char* msg) {
245 char buffer[SATB_PRINTER_BUFFER_SIZE];
246 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
247
248 tty->cr();
249 tty->print_cr("SATB BUFFERS [%s]", msg);
250
251 BufferNode* nd = _completed_buffers_head;
252 int i = 0;
253 while (nd != NULL) {
254 void** buf = BufferNode::make_buffer_from_node(nd);
255 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
256 print_satb_buffer(buffer, buf, nd->index(), buffer_size());
257 nd = nd->next();
258 i += 1;
259 }
260
261 CollectedHeap* heap = Universe::heap();
262 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
263 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
264 heap->satb_mark_queue(t)->print(buffer);
265 }
266
267 shared_satb_queue()->print("Shared");
268
269 tty->cr();
270 }
271 #endif // PRODUCT
272
273 void SATBMarkQueueSet::abandon_partial_marking() {
274 BufferNode* buffers_to_delete = NULL;
275 {
276 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
277 while (_completed_buffers_head != NULL) {
278 BufferNode* nd = _completed_buffers_head;
279 _completed_buffers_head = nd->next();
280 nd->set_next(buffers_to_delete);
281 buffers_to_delete = nd;
282 }
283 _completed_buffers_tail = NULL;
284 _n_completed_buffers = 0;
285 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
286 }
287 while (buffers_to_delete != NULL) {
288 BufferNode* nd = buffers_to_delete;
289 buffers_to_delete = nd->next();
290 deallocate_buffer(nd);
291 }
292 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
293 // So we can safely manipulate these queues.
294 CollectedHeap* heap = Universe::heap();
295 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
296 heap->satb_mark_queue(t)->reset();
297 }
298 shared_satb_queue()->reset();
299 }