75 CMCleanUp(G1ConcurrentMark* cm) :
76 _cm(cm) {}
77
78 void do_void(){
79 _cm->cleanup();
80 }
81 };
82
83 // Marking pauses can be scheduled flexibly, so we might delay marking to meet MMU.
84 void ConcurrentMarkThread::delay_to_keep_mmu(G1CollectorPolicy* g1_policy, bool remark) {
85 if (g1_policy->adaptive_young_list_length()) {
86 double now = os::elapsedTime();
87 double prediction_ms = remark ? g1_policy->predict_remark_time_ms()
88 : g1_policy->predict_cleanup_time_ms();
89 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
90 jlong sleep_time_ms = mmu_tracker->when_ms(now, prediction_ms);
91 os::sleep(this, sleep_time_ms, false);
92 }
93 }
94
95 class GCConcPhaseTimer : StackObj {
96 G1ConcurrentMark* _cm;
97
98 public:
99 GCConcPhaseTimer(G1ConcurrentMark* cm, const char* title) : _cm(cm) {
100 _cm->register_concurrent_phase_start(title);
101 }
102
103 ~GCConcPhaseTimer() {
104 _cm->register_concurrent_phase_end();
105 }
106 };
107
108 void ConcurrentMarkThread::run_service() {
109 _vtime_start = os::elapsedVTime();
110
111 G1CollectedHeap* g1h = G1CollectedHeap::heap();
112 G1CollectorPolicy* g1_policy = g1h->g1_policy();
113
114 while (!should_terminate()) {
115 // wait until started is set.
116 sleepBeforeNextCycle();
117 if (should_terminate()) {
118 _cm->root_regions()->cancel_scan();
119 break;
120 }
121
122 assert(GCId::current() != GCId::undefined(), "GC id should have been set up by the initial mark GC.");
123 {
124 ResourceMark rm;
125 HandleMark hm;
126 double cycle_start = os::elapsedVTime();
127
128 {
129 GCConcPhaseTimer(_cm, "Concurrent Clearing of Claimed Marks");
130 ClassLoaderDataGraph::clear_claimed_marks();
131 }
132
133 // We have to ensure that we finish scanning the root regions
134 // before the next GC takes place. To ensure this we have to
135 // make sure that we do not join the STS until the root regions
136 // have been scanned. If we did then it's possible that a
137 // subsequent GC could block us from joining the STS and proceed
138 // without the root regions have been scanned which would be a
139 // correctness issue.
140
141 {
142 GCConcPhaseTimer(_cm, "Concurrent Root Region Scanning");
143 _cm->scanRootRegions();
144 }
145
146 // It would be nice to use the GCTraceConcTime class here but
147 // the "end" logging is inside the loop and not at the end of
148 // a scope. Mimicking the same log output as GCTraceConcTime instead.
149 jlong mark_start = os::elapsed_counter();
150 log_info(gc)("Concurrent Mark (%.3fs)", TimeHelper::counter_to_seconds(mark_start));
151
152 int iter = 0;
153 do {
154 iter++;
155 if (!cm()->has_aborted()) {
156 GCConcPhaseTimer(_cm, "Concurrent Mark");
157 _cm->markFromRoots();
158 }
159
160 double mark_end_time = os::elapsedVTime();
161 jlong mark_end = os::elapsed_counter();
162 _vtime_mark_accum += (mark_end_time - cycle_start);
163 if (!cm()->has_aborted()) {
164 delay_to_keep_mmu(g1_policy, true /* remark */);
165 log_info(gc)("Concurrent Mark (%.3fs, %.3fs) %.3fms",
166 TimeHelper::counter_to_seconds(mark_start),
167 TimeHelper::counter_to_seconds(mark_end),
168 TimeHelper::counter_to_millis(mark_end - mark_start));
169
170 CMCheckpointRootsFinalClosure final_cl(_cm);
171 VM_CGC_Operation op(&final_cl, "Pause Remark", true /* needs_pll */);
172 VMThread::execute(&op);
173 }
174 if (cm()->restart_for_overflow()) {
175 log_debug(gc)("Restarting conc marking because of MS overflow in remark (restart #%d).", iter);
176 log_info(gc)("Concurrent Mark restart for overflow");
177 }
178 } while (cm()->restart_for_overflow());
179
180 double end_time = os::elapsedVTime();
181 // Update the total virtual time before doing this, since it will try
182 // to measure it to get the vtime for this marking. We purposely
183 // neglect the presumably-short "completeCleanup" phase here.
184 _vtime_accum = (end_time - _vtime_start);
185
186 if (!cm()->has_aborted()) {
187 delay_to_keep_mmu(g1_policy, false /* cleanup */);
188
189 CMCleanUp cl_cl(_cm);
190 VM_CGC_Operation op(&cl_cl, "Pause Cleanup", false /* needs_pll */);
191 VMThread::execute(&op);
192 } else {
193 // We don't want to update the marking status if a GC pause
194 // is already underway.
195 SuspendibleThreadSetJoiner sts_join;
196 g1h->collector_state()->set_mark_in_progress(false);
197 }
198
199 // Check if cleanup set the free_regions_coming flag. If it
200 // hasn't, we can just skip the next step.
201 if (g1h->free_regions_coming()) {
202 // The following will finish freeing up any regions that we
203 // found to be empty during cleanup. We'll do this part
204 // without joining the suspendible set. If an evacuation pause
205 // takes place, then we would carry on freeing regions in
206 // case they are needed by the pause. If a Full GC takes
207 // place, it would wait for us to process the regions
208 // reclaimed by cleanup.
209
210 GCTraceConcTime(Info, gc) tt("Concurrent Cleanup");
211 GCConcPhaseTimer(_cm, "Concurrent Cleanup");
212
213 // Now do the concurrent cleanup operation.
214 _cm->completeCleanup();
215
216 // Notify anyone who's waiting that there are no more free
217 // regions coming. We have to do this before we join the STS
218 // (in fact, we should not attempt to join the STS in the
219 // interval between finishing the cleanup pause and clearing
220 // the free_regions_coming flag) otherwise we might deadlock:
221 // a GC worker could be blocked waiting for the notification
222 // whereas this thread will be blocked for the pause to finish
223 // while it's trying to join the STS, which is conditional on
224 // the GC workers finishing.
225 g1h->reset_free_regions_coming();
226 }
227 guarantee(cm()->cleanup_list_is_empty(),
228 "at this point there should be no regions on the cleanup list");
229
230 // There is a tricky race before recording that the concurrent
231 // cleanup has completed and a potential Full GC starting around
232 // the same time. We want to make sure that the Full GC calls
233 // abort() on concurrent mark after
234 // record_concurrent_mark_cleanup_completed(), since abort() is
239 // the STS allows the correct ordering of the two methods. There
240 // are two scenarios:
241 //
242 // a) If we reach here before the Full GC, the fact that we have
243 // joined the STS means that the Full GC cannot start until we
244 // leave the STS, so record_concurrent_mark_cleanup_completed()
245 // will complete before abort() is called.
246 //
247 // b) If we reach here during the Full GC, we'll be held up from
248 // joining the STS until the Full GC is done, which means that
249 // abort() will have completed and has_aborted() will return
250 // true to prevent us from calling
251 // record_concurrent_mark_cleanup_completed() (and, in fact, it's
252 // not needed any more as the concurrent mark state has been
253 // already reset).
254 {
255 SuspendibleThreadSetJoiner sts_join;
256 if (!cm()->has_aborted()) {
257 g1_policy->record_concurrent_mark_cleanup_completed();
258 } else {
259 log_info(gc)("Concurrent Mark abort");
260 }
261 }
262
263 // We now want to allow clearing of the marking bitmap to be
264 // suspended by a collection pause.
265 // We may have aborted just before the remark. Do not bother clearing the
266 // bitmap then, as it has been done during mark abort.
267 if (!cm()->has_aborted()) {
268 GCConcPhaseTimer(_cm, "Concurrent Bitmap Clearing");
269 _cm->cleanup_for_next_mark();
270 } else {
271 assert(!G1VerifyBitmaps || _cm->nextMarkBitmapIsClear(), "Next mark bitmap must be clear");
272 }
273 }
274
275 // Update the number of full collections that have been
276 // completed. This will also notify the FullGCCount_lock in case a
277 // Java thread is waiting for a full GC to happen (e.g., it
278 // called System.gc() with +ExplicitGCInvokesConcurrent).
279 {
280 SuspendibleThreadSetJoiner sts_join;
281 g1h->increment_old_marking_cycles_completed(true /* concurrent */);
282 g1h->register_concurrent_cycle_end();
283 }
284 }
285 }
286
287 void ConcurrentMarkThread::stop_service() {
288 MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag);
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75 CMCleanUp(G1ConcurrentMark* cm) :
76 _cm(cm) {}
77
78 void do_void(){
79 _cm->cleanup();
80 }
81 };
82
83 // Marking pauses can be scheduled flexibly, so we might delay marking to meet MMU.
84 void ConcurrentMarkThread::delay_to_keep_mmu(G1CollectorPolicy* g1_policy, bool remark) {
85 if (g1_policy->adaptive_young_list_length()) {
86 double now = os::elapsedTime();
87 double prediction_ms = remark ? g1_policy->predict_remark_time_ms()
88 : g1_policy->predict_cleanup_time_ms();
89 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
90 jlong sleep_time_ms = mmu_tracker->when_ms(now, prediction_ms);
91 os::sleep(this, sleep_time_ms, false);
92 }
93 }
94
95 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
96 G1ConcurrentMark* _cm;
97
98 public:
99 G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
100 GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title),
101 _cm(cm) {
102 _cm->register_concurrent_phase_start(title);
103 }
104
105 ~G1ConcPhaseTimer() {
106 _cm->register_concurrent_phase_end();
107 }
108 };
109
110 void ConcurrentMarkThread::run_service() {
111 _vtime_start = os::elapsedVTime();
112
113 G1CollectedHeap* g1h = G1CollectedHeap::heap();
114 G1CollectorPolicy* g1_policy = g1h->g1_policy();
115
116 while (!should_terminate()) {
117 // wait until started is set.
118 sleepBeforeNextCycle();
119 if (should_terminate()) {
120 _cm->root_regions()->cancel_scan();
121 break;
122 }
123
124 assert(GCId::current() != GCId::undefined(), "GC id should have been set up by the initial mark GC.");
125
126 GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
127 {
128 ResourceMark rm;
129 HandleMark hm;
130 double cycle_start = os::elapsedVTime();
131
132 {
133 G1ConcPhaseTimer t(_cm, "Concurrent Clear Claimed Marks");
134 ClassLoaderDataGraph::clear_claimed_marks();
135 }
136
137 // We have to ensure that we finish scanning the root regions
138 // before the next GC takes place. To ensure this we have to
139 // make sure that we do not join the STS until the root regions
140 // have been scanned. If we did then it's possible that a
141 // subsequent GC could block us from joining the STS and proceed
142 // without the root regions have been scanned which would be a
143 // correctness issue.
144
145 {
146 G1ConcPhaseTimer t(_cm, "Concurrent Scan Root Regions");
147 _cm->scan_root_regions();
148 }
149
150 // It would be nice to use the GCTraceConcTime class here but
151 // the "end" logging is inside the loop and not at the end of
152 // a scope. Mimicking the same log output as GCTraceConcTime instead.
153 jlong mark_start = os::elapsed_counter();
154 log_info(gc, marking)("Concurrent Mark (%.3fs)", TimeHelper::counter_to_seconds(mark_start));
155
156 int iter = 0;
157 do {
158 iter++;
159 if (!cm()->has_aborted()) {
160 G1ConcPhaseTimer t(_cm, "Concurrent Mark From Roots");
161 _cm->mark_from_roots();
162 }
163
164 double mark_end_time = os::elapsedVTime();
165 jlong mark_end = os::elapsed_counter();
166 _vtime_mark_accum += (mark_end_time - cycle_start);
167 if (!cm()->has_aborted()) {
168 delay_to_keep_mmu(g1_policy, true /* remark */);
169 log_info(gc, marking)("Concurrent Mark (%.3fs, %.3fs) %.3fms",
170 TimeHelper::counter_to_seconds(mark_start),
171 TimeHelper::counter_to_seconds(mark_end),
172 TimeHelper::counter_to_millis(mark_end - mark_start));
173
174 CMCheckpointRootsFinalClosure final_cl(_cm);
175 VM_CGC_Operation op(&final_cl, "Pause Remark", true /* needs_pll */);
176 VMThread::execute(&op);
177 }
178 if (cm()->restart_for_overflow()) {
179 log_debug(gc, marking)("Restarting Concurrent Marking because of Mark Stack Overflow in Remark (Iteration #%d).", iter);
180 log_info(gc, marking)("Concurrent Mark Restart due to overflow");
181 }
182 } while (cm()->restart_for_overflow());
183
184 double end_time = os::elapsedVTime();
185 // Update the total virtual time before doing this, since it will try
186 // to measure it to get the vtime for this marking. We purposely
187 // neglect the presumably-short "completeCleanup" phase here.
188 _vtime_accum = (end_time - _vtime_start);
189
190 if (!cm()->has_aborted()) {
191 delay_to_keep_mmu(g1_policy, false /* cleanup */);
192
193 CMCleanUp cl_cl(_cm);
194 VM_CGC_Operation op(&cl_cl, "Pause Cleanup", false /* needs_pll */);
195 VMThread::execute(&op);
196 } else {
197 // We don't want to update the marking status if a GC pause
198 // is already underway.
199 SuspendibleThreadSetJoiner sts_join;
200 g1h->collector_state()->set_mark_in_progress(false);
201 }
202
203 // Check if cleanup set the free_regions_coming flag. If it
204 // hasn't, we can just skip the next step.
205 if (g1h->free_regions_coming()) {
206 // The following will finish freeing up any regions that we
207 // found to be empty during cleanup. We'll do this part
208 // without joining the suspendible set. If an evacuation pause
209 // takes place, then we would carry on freeing regions in
210 // case they are needed by the pause. If a Full GC takes
211 // place, it would wait for us to process the regions
212 // reclaimed by cleanup.
213
214 G1ConcPhaseTimer t(_cm, "Concurrent Complete Cleanup");
215 // Now do the concurrent cleanup operation.
216 _cm->complete_cleanup();
217
218 // Notify anyone who's waiting that there are no more free
219 // regions coming. We have to do this before we join the STS
220 // (in fact, we should not attempt to join the STS in the
221 // interval between finishing the cleanup pause and clearing
222 // the free_regions_coming flag) otherwise we might deadlock:
223 // a GC worker could be blocked waiting for the notification
224 // whereas this thread will be blocked for the pause to finish
225 // while it's trying to join the STS, which is conditional on
226 // the GC workers finishing.
227 g1h->reset_free_regions_coming();
228 }
229 guarantee(cm()->cleanup_list_is_empty(),
230 "at this point there should be no regions on the cleanup list");
231
232 // There is a tricky race before recording that the concurrent
233 // cleanup has completed and a potential Full GC starting around
234 // the same time. We want to make sure that the Full GC calls
235 // abort() on concurrent mark after
236 // record_concurrent_mark_cleanup_completed(), since abort() is
241 // the STS allows the correct ordering of the two methods. There
242 // are two scenarios:
243 //
244 // a) If we reach here before the Full GC, the fact that we have
245 // joined the STS means that the Full GC cannot start until we
246 // leave the STS, so record_concurrent_mark_cleanup_completed()
247 // will complete before abort() is called.
248 //
249 // b) If we reach here during the Full GC, we'll be held up from
250 // joining the STS until the Full GC is done, which means that
251 // abort() will have completed and has_aborted() will return
252 // true to prevent us from calling
253 // record_concurrent_mark_cleanup_completed() (and, in fact, it's
254 // not needed any more as the concurrent mark state has been
255 // already reset).
256 {
257 SuspendibleThreadSetJoiner sts_join;
258 if (!cm()->has_aborted()) {
259 g1_policy->record_concurrent_mark_cleanup_completed();
260 } else {
261 log_info(gc, marking)("Concurrent Mark Abort");
262 }
263 }
264
265 // We now want to allow clearing of the marking bitmap to be
266 // suspended by a collection pause.
267 // We may have aborted just before the remark. Do not bother clearing the
268 // bitmap then, as it has been done during mark abort.
269 if (!cm()->has_aborted()) {
270 G1ConcPhaseTimer t(_cm, "Concurrent Cleanup for Next Mark");
271 _cm->cleanup_for_next_mark();
272 } else {
273 assert(!G1VerifyBitmaps || _cm->nextMarkBitmapIsClear(), "Next mark bitmap must be clear");
274 }
275 }
276
277 // Update the number of full collections that have been
278 // completed. This will also notify the FullGCCount_lock in case a
279 // Java thread is waiting for a full GC to happen (e.g., it
280 // called System.gc() with +ExplicitGCInvokesConcurrent).
281 {
282 SuspendibleThreadSetJoiner sts_join;
283 g1h->increment_old_marking_cycles_completed(true /* concurrent */);
284 g1h->register_concurrent_cycle_end();
285 }
286 }
287 }
288
289 void ConcurrentMarkThread::stop_service() {
290 MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag);
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