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 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 }