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
46 // ======= Concurrent Mark Thread ========
47
48 G1ConcurrentMarkThread::G1ConcurrentMarkThread(G1ConcurrentMark* cm) :
49 ConcurrentGCThread(),
50 _vtime_start(0.0),
51 _vtime_accum(0.0),
52 _vtime_mark_accum(0.0),
53 _cm(cm),
54 _state(Idle)
55 {
56 set_name("G1 Main Marker");
57 create_and_start();
58 }
59
60 class CMRemark : public VoidClosure {
61 G1ConcurrentMark* _cm;
62 public:
63 CMRemark(G1ConcurrentMark* cm) : _cm(cm) {}
64
65 void do_void(){
66 _cm->remark();
67 }
68 };
69
70 class CMCleanup : public VoidClosure {
71 G1ConcurrentMark* _cm;
72 public:
73 CMCleanup(G1ConcurrentMark* cm) : _cm(cm) {}
74
75 void do_void(){
76 _cm->cleanup();
77 }
78 };
79
80 double G1ConcurrentMarkThread::mmu_delay_end(G1Policy* g1_policy, bool remark) {
81 // There are 3 reasons to use SuspendibleThreadSetJoiner.
82 // 1. To avoid concurrency problem.
83 // - G1MMUTracker::add_pause(), when_sec() and its variation(when_ms() etc..) can be called
84 // concurrently from ConcurrentMarkThread and VMThread.
85 // 2. If currently a gc is running, but it has not yet updated the MMU,
86 // we will not forget to consider that pause in the MMU calculation.
87 // 3. If currently a gc is running, ConcurrentMarkThread will wait it to be finished.
88 // And then sleep for predicted amount of time by delay_to_keep_mmu().
89 SuspendibleThreadSetJoiner sts_join;
90
91 const G1Analytics* analytics = g1_policy->analytics();
92 double prediction_ms = remark ? analytics->predict_remark_time_ms()
93 : analytics->predict_cleanup_time_ms();
94 double prediction = prediction_ms / MILLIUNITS;
95 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
96 double now = os::elapsedTime();
97 return now + mmu_tracker->when_sec(now, prediction);
98 }
99
100 void G1ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) {
101 if (g1_policy->use_adaptive_young_list_length()) {
102 double delay_end_sec = mmu_delay_end(g1_policy, remark);
103 // Wait for timeout or thread termination request.
104 MonitorLocker ml(CGC_lock, Monitor::_no_safepoint_check_flag);
105 while (!_cm->has_aborted()) {
106 double sleep_time_sec = (delay_end_sec - os::elapsedTime());
107 jlong sleep_time_ms = ceil(sleep_time_sec * MILLIUNITS);
108 if (sleep_time_ms <= 0) {
109 break; // Passed end time.
110 } else if (ml.wait(sleep_time_ms, Monitor::_no_safepoint_check_flag)) {
111 break; // Timeout => reached end time.
112 } else if (should_terminate()) {
113 break; // Wakeup for pending termination request.
114 }
115 // Other (possibly spurious) wakeup. Retry with updated sleep time.
116 }
117 }
118 }
119
120 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
121 G1ConcurrentMark* _cm;
122
123 public:
124 G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
125 GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title),
126 _cm(cm)
127 {
128 _cm->gc_timer_cm()->register_gc_concurrent_start(title);
129 }
130
131 ~G1ConcPhaseTimer() {
132 _cm->gc_timer_cm()->register_gc_concurrent_end();
133 }
134 };
135
136 void G1ConcurrentMarkThread::run_service() {
137 _vtime_start = os::elapsedVTime();
138
139 G1CollectedHeap* g1h = G1CollectedHeap::heap();
140 G1Policy* policy = g1h->policy();
141
142 while (!should_terminate()) {
143 // wait until started is set.
144 sleep_before_next_cycle();
145 if (should_terminate()) {
146 break;
147 }
148
149 GCIdMark gc_id_mark;
150
151 _cm->concurrent_cycle_start();
152
153 GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
154 {
155 ResourceMark rm;
156
157 double cycle_start = os::elapsedVTime();
158
159 {
160 G1ConcPhaseTimer p(_cm, "Concurrent Clear Claimed Marks");
161 ClassLoaderDataGraph::clear_claimed_marks();
162 }
163
164 // We have to ensure that we finish scanning the root regions
165 // before the next GC takes place. To ensure this we have to
166 // make sure that we do not join the STS until the root regions
167 // have been scanned. If we did then it's possible that a
168 // subsequent GC could block us from joining the STS and proceed
169 // without the root regions have been scanned which would be a
170 // correctness issue.
171
172 {
173 G1ConcPhaseTimer p(_cm, "Concurrent Scan Root Regions");
174 _cm->scan_root_regions();
175 }
176
177 // Note: ConcurrentGCBreakpoints before here risk deadlock,
178 // because a young GC must wait for root region scanning.
179
180 // It would be nice to use the G1ConcPhaseTimer class here but
181 // the "end" logging is inside the loop and not at the end of
182 // a scope. Also, the timer doesn't support nesting.
183 // Mimicking the same log output instead.
184 jlong mark_start = os::elapsed_counter();
185 log_info(gc, marking)("Concurrent Mark (%.3fs)",
186 TimeHelper::counter_to_seconds(mark_start));
187 for (uint iter = 1; !_cm->has_aborted(); ++iter) {
188 // Concurrent marking.
189 {
190 ConcurrentGCBreakpoints::at("AFTER MARKING STARTED");
191 G1ConcPhaseTimer p(_cm, "Concurrent Mark From Roots");
192 _cm->mark_from_roots();
193 }
194 if (_cm->has_aborted()) {
195 break;
196 }
197
198 if (G1UseReferencePrecleaning) {
199 G1ConcPhaseTimer p(_cm, "Concurrent Preclean");
200 _cm->preclean();
201 }
202 if (_cm->has_aborted()) {
203 break;
204 }
205
206 // Delay remark pause for MMU.
207 double mark_end_time = os::elapsedVTime();
208 jlong mark_end = os::elapsed_counter();
209 _vtime_mark_accum += (mark_end_time - cycle_start);
210 delay_to_keep_mmu(policy, true /* remark */);
211 if (_cm->has_aborted()) {
212 break;
213 }
214
215 // Pause Remark.
216 ConcurrentGCBreakpoints::at("BEFORE MARKING COMPLETED");
217 log_info(gc, marking)("Concurrent Mark (%.3fs, %.3fs) %.3fms",
218 TimeHelper::counter_to_seconds(mark_start),
219 TimeHelper::counter_to_seconds(mark_end),
220 TimeHelper::counter_to_millis(mark_end - mark_start));
221 CMRemark cl(_cm);
222 VM_G1Concurrent op(&cl, "Pause Remark");
223 VMThread::execute(&op);
224 if (_cm->has_aborted()) {
225 break;
226 } else if (!_cm->restart_for_overflow()) {
227 break; // Exit loop if no restart requested.
228 } else {
229 // Loop to restart for overflow.
230 log_info(gc, marking)("Concurrent Mark Restart for Mark Stack Overflow (iteration #%u)",
231 iter);
232 }
233 }
234
235 if (!_cm->has_aborted()) {
236 G1ConcPhaseTimer p(_cm, "Concurrent Rebuild Remembered Sets");
237 _cm->rebuild_rem_set_concurrently();
238 }
239
240 double end_time = os::elapsedVTime();
241 // Update the total virtual time before doing this, since it will try
242 // to measure it to get the vtime for this marking.
243 _vtime_accum = (end_time - _vtime_start);
244
245 if (!_cm->has_aborted()) {
246 delay_to_keep_mmu(policy, false /* cleanup */);
247 }
248
249 if (!_cm->has_aborted()) {
250 CMCleanup cl_cl(_cm);
251 VM_G1Concurrent op(&cl_cl, "Pause Cleanup");
252 VMThread::execute(&op);
253 }
254
255 // We now want to allow clearing of the marking bitmap to be
256 // suspended by a collection pause.
257 // We may have aborted just before the remark. Do not bother clearing the
258 // bitmap then, as it has been done during mark abort.
259 if (!_cm->has_aborted()) {
260 G1ConcPhaseTimer p(_cm, "Concurrent Cleanup for Next Mark");
261 _cm->cleanup_for_next_mark();
262 }
263 }
264
265 // Update the number of full collections that have been
266 // completed. This will also notify the G1OldGCCount_lock in case a
267 // Java thread is waiting for a full GC to happen (e.g., it
268 // called System.gc() with +ExplicitGCInvokesConcurrent).
269 {
270 SuspendibleThreadSetJoiner sts_join;
271 g1h->increment_old_marking_cycles_completed(true /* concurrent */,
272 !_cm->has_aborted() /* liveness_completed */);
273
274 _cm->concurrent_cycle_end();
275 ConcurrentGCBreakpoints::notify_active_to_idle();
276 }
277 }
278 _cm->root_regions()->cancel_scan();
279 }
280
281 void G1ConcurrentMarkThread::stop_service() {
282 MutexLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
283 CGC_lock->notify_all();
284 }
285
286
287 void G1ConcurrentMarkThread::sleep_before_next_cycle() {
288 // We join here because we don't want to do the "shouldConcurrentMark()"
289 // below while the world is otherwise stopped.
290 assert(!in_progress(), "should have been cleared");
291
292 MonitorLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
293 while (!started() && !should_terminate()) {
294 ml.wait();
295 }
296
297 if (started()) {
298 set_in_progress();
299 }
300 }
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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 G1ConcurrentMarkThread::G1ConcurrentMarkThread(G1ConcurrentMark* cm) :
48 ConcurrentGCThread(),
49 _vtime_start(0.0),
50 _vtime_accum(0.0),
51 _cm(cm),
52 _state(Idle)
53 {
54 set_name("G1 Main Marker");
55 create_and_start();
56 }
57
58 class CMRemark : public VoidClosure {
59 G1ConcurrentMark* _cm;
60 public:
61 CMRemark(G1ConcurrentMark* cm) : _cm(cm) {}
62
63 void do_void(){
64 _cm->remark();
65 }
66 };
67
68 class CMCleanup : public VoidClosure {
69 G1ConcurrentMark* _cm;
70 public:
71 CMCleanup(G1ConcurrentMark* cm) : _cm(cm) {}
72
73 void do_void(){
74 _cm->cleanup();
75 }
76 };
77
78 double G1ConcurrentMarkThread::mmu_delay_end(G1Policy* policy, bool remark) {
79 // There are 3 reasons to use SuspendibleThreadSetJoiner.
80 // 1. To avoid concurrency problem.
81 // - G1MMUTracker::add_pause(), when_sec() and its variation(when_ms() etc..) can be called
82 // concurrently from ConcurrentMarkThread and VMThread.
83 // 2. If currently a gc is running, but it has not yet updated the MMU,
84 // we will not forget to consider that pause in the MMU calculation.
85 // 3. If currently a gc is running, ConcurrentMarkThread will wait it to be finished.
86 // And then sleep for predicted amount of time by delay_to_keep_mmu().
87 SuspendibleThreadSetJoiner sts_join;
88
89 const G1Analytics* analytics = policy->analytics();
90 double prediction_ms = remark ? analytics->predict_remark_time_ms()
91 : analytics->predict_cleanup_time_ms();
92 double prediction = prediction_ms / MILLIUNITS;
93 G1MMUTracker *mmu_tracker = policy->mmu_tracker();
94 double now = os::elapsedTime();
95 return now + mmu_tracker->when_sec(now, prediction);
96 }
97
98 void G1ConcurrentMarkThread::delay_to_keep_mmu(bool remark) {
99 G1Policy* policy = G1CollectedHeap::heap()->policy();
100
101 if (policy->use_adaptive_young_list_length()) {
102 double delay_end_sec = mmu_delay_end(policy, remark);
103 // Wait for timeout or thread termination request.
104 MonitorLocker ml(CGC_lock, Monitor::_no_safepoint_check_flag);
105 while (!_cm->has_aborted() && !should_terminate()) {
106 double sleep_time_sec = (delay_end_sec - os::elapsedTime());
107 jlong sleep_time_ms = ceil(sleep_time_sec * MILLIUNITS);
108 if (sleep_time_ms <= 0) {
109 break; // Passed end time.
110 } else if (ml.wait(sleep_time_ms, Monitor::_no_safepoint_check_flag)) {
111 break; // Timeout => reached end time.
112 }
113 // Other (possibly spurious) wakeup. Retry with updated sleep time.
114 }
115 }
116 }
117
118 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
119 G1ConcurrentMark* _cm;
120
121 public:
122 G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
123 GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title),
124 _cm(cm)
125 {
126 _cm->gc_timer_cm()->register_gc_concurrent_start(title);
127 }
128
129 ~G1ConcPhaseTimer() {
130 _cm->gc_timer_cm()->register_gc_concurrent_end();
131 }
132 };
133
134 void G1ConcurrentMarkThread::run_service() {
135 _vtime_start = os::elapsedVTime();
136
137 while (!should_terminate()) {
138 if (wait_for_next_cycle()) {
139 break;
140 }
141
142 GCIdMark gc_id_mark;
143 GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
144
145 concurrent_cycle_start();
146 full_concurrent_cycle_do();
147 concurrent_cycle_end();
148
149 _vtime_accum = (os::elapsedVTime() - _vtime_start);
150 }
151 _cm->root_regions()->cancel_scan();
152 }
153
154 void G1ConcurrentMarkThread::stop_service() {
155 MutexLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
156 CGC_lock->notify_all();
157 }
158
159 bool G1ConcurrentMarkThread::wait_for_next_cycle() {
160 assert(!in_progress(), "should have been cleared");
161
162 MonitorLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
163 while (!started() && !should_terminate()) {
164 ml.wait();
165 }
166
167 if (started()) {
168 set_in_progress();
169 }
170
171 return should_terminate();
172 }
173
174 bool G1ConcurrentMarkThread::phase_clear_cld_claimed_marks() {
175 G1ConcPhaseTimer p(_cm, "Concurrent Clear Claimed Marks");
176 ClassLoaderDataGraph::clear_claimed_marks();
177 return _cm->has_aborted();
178 }
179
180 bool G1ConcurrentMarkThread::phase_scan_root_regions() {
181 G1ConcPhaseTimer p(_cm, "Concurrent Scan Root Regions");
182 _cm->scan_root_regions();
183 return _cm->has_aborted();
184 }
185
186 bool G1ConcurrentMarkThread::phase_mark_loop() {
187 Ticks mark_start = Ticks::now();
188 log_info(gc, marking)("Concurrent Mark (%.3fs)", mark_start.seconds());
189
190 uint iter = 1;
191 while (true) {
192 // Subphase 1: Mark From Roots.
193 if (subphase_mark_from_roots()) return true;
194
195 // Subphase 2: Preclean (optional)
196 if (G1UseReferencePrecleaning) {
197 if (subphase_preclean()) return true;
198 }
199
200 // Subphase 3: Wait for Remark.
201 if (subphase_delay_to_keep_mmu_before_remark()) return true;
202
203 // Subphase 4: Remark pause
204 if (subphase_remark()) return true;
205
206 // Check if we need to restart the marking loop.
207 if (!mark_loop_needs_restart()) break;
208
209 log_info(gc, marking)("Concurrent Mark Restart for Mark Stack Overflow (iteration #%u)",
210 iter++);
211 }
212
213 Ticks mark_end = Ticks::now();
214 log_info(gc, marking)("Concurrent Mark (%.3fs, %.3fs) %.3fms",
215 mark_start.seconds(), mark_end.seconds(),
216 (mark_end - mark_start).seconds() * 1000.0);
217
218 return false;
219 }
220
221 bool G1ConcurrentMarkThread::mark_loop_needs_restart() const {
222 return _cm->has_overflown();
223 }
224
225 bool G1ConcurrentMarkThread::subphase_mark_from_roots() {
226 ConcurrentGCBreakpoints::at("AFTER MARKING STARTED");
227 G1ConcPhaseTimer p(_cm, "Concurrent Mark From Roots");
228 _cm->mark_from_roots();
229 return _cm->has_aborted();
230 }
231
232 bool G1ConcurrentMarkThread::subphase_preclean() {
233 G1ConcPhaseTimer p(_cm, "Concurrent Preclean");
234 _cm->preclean();
235 return _cm->has_aborted();
236 }
237
238 bool G1ConcurrentMarkThread::subphase_delay_to_keep_mmu_before_remark() {
239 delay_to_keep_mmu(true /* remark */);
240 return _cm->has_aborted();
241 }
242
243 bool G1ConcurrentMarkThread::subphase_remark() {
244 ConcurrentGCBreakpoints::at("BEFORE MARKING COMPLETED");
245 CMRemark cl(_cm);
246 VM_G1Concurrent op(&cl, "Pause Remark");
247 VMThread::execute(&op);
248 return _cm->has_aborted();
249 }
250
251 bool G1ConcurrentMarkThread::phase_rebuild_remembered_sets() {
252 G1ConcPhaseTimer p(_cm, "Concurrent Rebuild Remembered Sets");
253 _cm->rebuild_rem_set_concurrently();
254 return _cm->has_aborted();
255 }
256
257 bool G1ConcurrentMarkThread::phase_delay_to_keep_mmu_before_cleanup() {
258 delay_to_keep_mmu(false /* cleanup */);
259 return _cm->has_aborted();
260 }
261
262 bool G1ConcurrentMarkThread::phase_cleanup() {
263 CMCleanup cl(_cm);
264 VM_G1Concurrent op(&cl, "Pause Cleanup");
265 VMThread::execute(&op);
266 return _cm->has_aborted();
267 }
268
269 bool G1ConcurrentMarkThread::phase_clear_bitmap_for_next_mark() {
270 G1ConcPhaseTimer p(_cm, "Concurrent Cleanup for Next Mark");
271 _cm->cleanup_for_next_mark();
272 return _cm->has_aborted();
273 }
274
275 void G1ConcurrentMarkThread::concurrent_cycle_start() {
276 _cm->concurrent_cycle_start();
277 }
278
279 void G1ConcurrentMarkThread::full_concurrent_cycle_do() {
280 HandleMark hm(Thread::current());
281 ResourceMark rm;
282
283 // Phase 1: Clear CLD claimed marks.
284 phase_clear_cld_claimed_marks();
285
286 // Do not return before the scan root regions phase as a GC waits for a
287 // notification from it.
288
289 // Phase 2: Scan root regions.
290 if (phase_scan_root_regions()) return;
291
292 // Phase 3: Actual mark loop.
293 if (phase_mark_loop()) return;
294
295 // Phase 4: Rebuild remembered sets.
296 if (phase_rebuild_remembered_sets()) return;
297
298 // Phase 5: Wait for Cleanup.
299 if (phase_delay_to_keep_mmu_before_cleanup()) return;
300
301 // Phase 6: Cleanup pause
302 if (phase_cleanup()) return;
303
304 // Phase 7: Clear bitmap for next mark.
305 phase_clear_bitmap_for_next_mark();
306 }
307
308 void G1ConcurrentMarkThread::concurrent_cycle_end() {
309 // Update the number of full collections that have been
310 // completed. This will also notify the G1OldGCCount_lock in case a
311 // Java thread is waiting for a full GC to happen (e.g., it
312 // called System.gc() with +ExplicitGCInvokesConcurrent).
313 SuspendibleThreadSetJoiner sts_join;
314 G1CollectedHeap::heap()->increment_old_marking_cycles_completed(true /* concurrent */,
315 !_cm->has_aborted());
316
317 _cm->concurrent_cycle_end();
318 ConcurrentGCBreakpoints::notify_active_to_idle();
319 }
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