1 /*
2 * Copyright (c) 2001, 2020, 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 "classfile/classLoaderDataGraph.hpp"
27 #include "gc/g1/g1Analytics.hpp"
28 #include "gc/g1/g1CollectedHeap.inline.hpp"
29 #include "gc/g1/g1ConcurrentMark.inline.hpp"
30 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
31 #include "gc/g1/g1MMUTracker.hpp"
32 #include "gc/g1/g1Policy.hpp"
33 #include "gc/g1/g1RemSet.hpp"
34 #include "gc/g1/g1Trace.hpp"
35 #include "gc/g1/g1VMOperations.hpp"
36 #include "gc/shared/concurrentGCBreakpoints.hpp"
37 #include "gc/shared/gcId.hpp"
38 #include "gc/shared/gcTraceTime.inline.hpp"
39 #include "gc/shared/suspendibleThreadSet.hpp"
40 #include "logging/log.hpp"
41 #include "memory/resourceArea.hpp"
42 #include "runtime/handles.inline.hpp"
43 #include "runtime/vmThread.hpp"
44 #include "utilities/debug.hpp"
45 #include "utilities/ticks.hpp"
46
47 // ======= Concurrent Mark Thread ========
48
49 G1ConcurrentMarkThread::G1ConcurrentMarkThread(G1ConcurrentMark* cm) :
50 ConcurrentGCThread(),
51 _vtime_start(0.0),
52 _vtime_accum(0.0),
53 _vtime_mark_accum(0.0),
54 _cm(cm),
55 _state(Idle)
56 {
57 set_name("G1 Main Marker");
58 create_and_start();
59 }
60
61 class CMRemark : public VoidClosure {
62 G1ConcurrentMark* _cm;
63 public:
64 CMRemark(G1ConcurrentMark* cm) : _cm(cm) {}
65
66 void do_void(){
67 _cm->remark();
68 }
69 };
70
71 class CMCleanup : public VoidClosure {
72 G1ConcurrentMark* _cm;
73 public:
74 CMCleanup(G1ConcurrentMark* cm) : _cm(cm) {}
75
76 void do_void(){
77 _cm->cleanup();
78 }
79 };
80
81 double G1ConcurrentMarkThread::mmu_delay_end(G1Policy* g1_policy, bool remark) {
82 // There are 3 reasons to use SuspendibleThreadSetJoiner.
83 // 1. To avoid concurrency problem.
84 // - G1MMUTracker::add_pause(), when_sec() and its variation(when_ms() etc..) can be called
85 // concurrently from ConcurrentMarkThread and VMThread.
86 // 2. If currently a gc is running, but it has not yet updated the MMU,
87 // we will not forget to consider that pause in the MMU calculation.
88 // 3. If currently a gc is running, ConcurrentMarkThread will wait it to be finished.
89 // And then sleep for predicted amount of time by delay_to_keep_mmu().
90 SuspendibleThreadSetJoiner sts_join;
91
92 const G1Analytics* analytics = g1_policy->analytics();
93 double prediction_ms = remark ? analytics->predict_remark_time_ms()
94 : analytics->predict_cleanup_time_ms();
95 double prediction = prediction_ms / MILLIUNITS;
96 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
97 double now = os::elapsedTime();
98 return now + mmu_tracker->when_sec(now, prediction);
99 }
100
101 void G1ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) {
102 if (g1_policy->use_adaptive_young_list_length()) {
103 double delay_end_sec = mmu_delay_end(g1_policy, remark);
104 // Wait for timeout or thread termination request.
105 MonitorLocker ml(CGC_lock, Monitor::_no_safepoint_check_flag);
106 while (!_cm->has_aborted() && !should_terminate()) {
107 double sleep_time_sec = (delay_end_sec - os::elapsedTime());
108 jlong sleep_time_ms = ceil(sleep_time_sec * MILLIUNITS);
109 if (sleep_time_ms <= 0) {
110 break; // Passed end time.
111 } else if (ml.wait(sleep_time_ms, Monitor::_no_safepoint_check_flag)) {
112 break; // Timeout => reached end time.
113 }
114 // Other (possibly spurious) wakeup. Retry with updated sleep time.
115 }
116 }
117 }
118
119 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
120 G1ConcurrentMark* _cm;
121
122 public:
123 G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
124 GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title),
125 _cm(cm)
126 {
127 _cm->gc_timer_cm()->register_gc_concurrent_start(title);
128 }
129
130 ~G1ConcPhaseTimer() {
131 _cm->gc_timer_cm()->register_gc_concurrent_end();
132 }
133 };
134
135 void G1ConcurrentMarkThread::run_service() {
136 _vtime_start = os::elapsedVTime();
137
138 while (!should_terminate()) {
139 if (wait_for_next_cycle()) {
140 break;
141 }
142 run_cycle();
143 }
144 _cm->root_regions()->cancel_scan();
145 }
146
147 void G1ConcurrentMarkThread::stop_service() {
148 MutexLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
149 CGC_lock->notify_all();
150 }
151
152 bool G1ConcurrentMarkThread::wait_for_next_cycle() {
153 assert(!in_progress(), "should have been cleared");
154
155 MonitorLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
156 while (!started() && !should_terminate()) {
157 ml.wait();
158 }
159
160 if (started()) {
161 set_in_progress();
162 }
163
164 return should_terminate();
165 }
166
167 void G1ConcurrentMarkThread::run_cycle() {
168 enum ConcurrentCyclePhase {
169 CycleStart,
170 CLDClearClaimedMarks,
171 ScanRootRegions,
172 MarkFromRoots,
173 Preclean,
174 DelayToKeepMMUBeforeRemark,
175 PauseRemark,
176 RebuildRememberedSets,
177 DelayToKeepMMUBeforeCleanup,
178 PauseCleanup,
179 CleanupForNextMark,
180 CycleDone
181 };
182
183 G1CollectedHeap* g1h = G1CollectedHeap::heap();
184 G1Policy* policy = g1h->policy();
185
186 ConcurrentCyclePhase cur_state = CycleStart;
187 ConcurrentCyclePhase next_state;
188
189 GCIdMark gc_id_mark;
190
191 GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
192 double cycle_start;
193
194 Ticks mark_start;
195 Ticks mark_end;
196 uint iter = 1;
197
198 while (!_cm->has_aborted() && cur_state != CycleDone) {
199 HandleMark hm;
200 ResourceMark rm;
201
202 switch (cur_state) {
203 case CycleStart: {
204 concurrent_cycle_start();
205 next_state = CLDClearClaimedMarks;
206 break;
207 }
208 case CLDClearClaimedMarks: {
209 G1ConcPhaseTimer p(_cm, "Concurrent Clear Claimed Marks");
210 ClassLoaderDataGraph::clear_claimed_marks();
211 next_state = ScanRootRegions;
212 break;
213 }
214 case ScanRootRegions: {
215 G1ConcPhaseTimer p(_cm, "Concurrent Scan Root Regions");
216 _cm->scan_root_regions();
217
218 // Note: ConcurrentGCBreakpoints before here risk deadlock,
219 // because a young GC must wait for root region scanning.
220
221 // It would be nice to use the G1ConcPhaseTimer class here but
222 // the "end" logging is inside the loop and not at the end of
223 // a scope.
224 cycle_start = os::elapsedVTime();
225 mark_start = Ticks::now()();
226 log_info(gc, marking)("Concurrent Mark (%.3fs)", mark_start.seconds());
227 next_state = MarkFromRoots;
228 break;
229 }
230 case MarkFromRoots: {
231 ConcurrentGCBreakpoints::at("AFTER MARKING STARTED");
232 G1ConcPhaseTimer p(_cm, "Concurrent Mark From Roots");
233 _cm->mark_from_roots();
234 next_state = G1UseReferencePrecleaning ? Preclean : DelayToKeepMMUBeforeRemark;
235 break;
236 }
237 case Preclean: {
238 G1ConcPhaseTimer p(_cm, "Concurrent Preclean");
239 _cm->preclean();
240 next_state = DelayToKeepMMUBeforeRemark;
241 break;
242 }
243 case DelayToKeepMMUBeforeRemark: {
244 double mark_end_time = os::elapsedVTime();
245 mark_end = Ticks::now();
246 _vtime_mark_accum += (mark_end_time - cycle_start);
247 delay_to_keep_mmu(policy, true /* remark */);
248 next_state = PauseRemark;
249 break;
250 }
251 case PauseRemark: {
252 // Pause Remark.
253 ConcurrentGCBreakpoints::at("BEFORE MARKING COMPLETED");
254 log_info(gc, marking)("Concurrent Mark (%.3fs, %.3fs) %.3fms",
255 mark_start.seconds(),
256 mark_end.seconds(),
257 (mark_end - mark_start).seconds() * 1000.0);
258 CMRemark cl(_cm);
259 VM_G1Concurrent op(&cl, "Pause Remark");
260 VMThread::execute(&op);
261 if (_cm->restart_for_overflow()) {
262 log_info(gc, marking)("Concurrent Mark Restart for Mark Stack Overflow (iteration #%u)",
263 iter);
264 iter++;
265 next_state = MarkFromRoots;
266 } else {
267 next_state = RebuildRememberedSets;
268 }
269 break;
270 }
271 case RebuildRememberedSets: {
272 G1ConcPhaseTimer p(_cm, "Concurrent Rebuild Remembered Sets");
273 _cm->rebuild_rem_set_concurrently();
274 next_state = DelayToKeepMMUBeforeCleanup;
275 break;
276 }
277 case DelayToKeepMMUBeforeCleanup: {
278 double end_time = os::elapsedVTime();
279 // Update the total virtual time before doing this, since it will try
280 // to measure it to get the vtime for this marking.
281 _vtime_accum = (end_time - _vtime_start);
282 delay_to_keep_mmu(policy, false /* cleanup */);
283 next_state = PauseCleanup;
284 break;
285 }
286 case PauseCleanup: {
287 CMCleanup cl_cl(_cm);
288 VM_G1Concurrent op(&cl_cl, "Pause Cleanup");
289 VMThread::execute(&op);
290 next_state = CleanupForNextMark;
291 break;
292 }
293 case CleanupForNextMark: {
294 G1ConcPhaseTimer p(_cm, "Concurrent Cleanup for Next Mark");
295 _cm->cleanup_for_next_mark();
296 next_state = CycleDone;
297 break;
298 }
299 default: {
300 guarantee(false, "Invalid state %u", cur_state);
301 break;
302 }
303 }
304 cur_state = next_state;
305 }
306
307 concurrent_cycle_end();
308 }
309
310 void G1ConcurrentMarkThread::concurrent_cycle_start() {
311 _cm->concurrent_cycle_start();
312 }
313
314 void G1ConcurrentMarkThread::concurrent_cycle_end() {
315 // Update the number of full collections that have been
316 // completed. This will also notify the G1OldGCCount_lock in case a
317 // Java thread is waiting for a full GC to happen (e.g., it
318 // called System.gc() with +ExplicitGCInvokesConcurrent).
319 SuspendibleThreadSetJoiner sts_join;
320 G1CollectedHeap::heap()->increment_old_marking_cycles_completed(true /* concurrent */,
321 !_cm->has_aborted() /* liveness_complete */);
322
323 _cm->concurrent_cycle_end();
324 ConcurrentGCBreakpoints::notify_active_to_idle();
325 }