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 "classfile/classLoaderData.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/vm_operations_g1.hpp" 35 #include "gc/shared/concurrentGCPhaseManager.hpp" 36 #include "gc/shared/gcId.hpp" 37 #include "gc/shared/gcTrace.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 // Check order in EXPAND_CURRENT_PHASES 49 STATIC_ASSERT(ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE < 50 ConcurrentGCPhaseManager::IDLE_PHASE); 51 52 #define EXPAND_CONCURRENT_PHASES(expander) \ 53 expander(ANY, = ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE, NULL) \ 54 expander(IDLE, = ConcurrentGCPhaseManager::IDLE_PHASE, NULL) \ 55 expander(CONCURRENT_CYCLE,, "Concurrent Cycle") \ 56 expander(CLEAR_CLAIMED_MARKS,, "Concurrent Clear Claimed Marks") \ 57 expander(SCAN_ROOT_REGIONS,, "Concurrent Scan Root Regions") \ 58 expander(CONCURRENT_MARK,, "Concurrent Mark") \ 59 expander(MARK_FROM_ROOTS,, "Concurrent Mark From Roots") \ 60 expander(BEFORE_REMARK,, NULL) \ 61 expander(REMARK,, NULL) \ 62 expander(REBUILD_REMEMBERED_SETS,, "Concurrent Rebuild Remembered Sets") \ 63 expander(CLEANUP_FOR_NEXT_MARK,, "Concurrent Cleanup for Next Mark") \ 64 /* */ 65 66 class G1ConcurrentPhase : public AllStatic { 67 public: 68 enum { 69 #define CONCURRENT_PHASE_ENUM(tag, value, ignore_title) tag value, 70 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_ENUM) 71 #undef CONCURRENT_PHASE_ENUM 72 PHASE_ID_LIMIT 73 }; 74 }; 75 76 // The CM thread is created when the G1 garbage collector is used 77 78 G1ConcurrentMarkThread::G1ConcurrentMarkThread(G1ConcurrentMark* cm) : 79 ConcurrentGCThread(), 80 _cm(cm), 81 _state(Idle), 82 _phase_manager_stack(), 83 _vtime_accum(0.0), 84 _vtime_mark_accum(0.0) { 85 86 set_name("G1 Main Marker"); 87 create_and_start(); 88 } 89 90 class CMRemark : public VoidClosure { 91 G1ConcurrentMark* _cm; 92 public: 93 CMRemark(G1ConcurrentMark* cm) : _cm(cm) {} 94 95 void do_void(){ 96 _cm->remark(); 97 } 98 }; 99 100 class CMCleanup : public VoidClosure { 101 G1ConcurrentMark* _cm; 102 public: 103 CMCleanup(G1ConcurrentMark* cm) : _cm(cm) {} 104 105 void do_void(){ 106 _cm->cleanup(); 107 } 108 }; 109 110 double G1ConcurrentMarkThread::mmu_sleep_time(G1Policy* g1_policy, bool remark) { 111 // There are 3 reasons to use SuspendibleThreadSetJoiner. 112 // 1. To avoid concurrency problem. 113 // - G1MMUTracker::add_pause(), when_sec() and its variation(when_ms() etc..) can be called 114 // concurrently from ConcurrentMarkThread and VMThread. 115 // 2. If currently a gc is running, but it has not yet updated the MMU, 116 // we will not forget to consider that pause in the MMU calculation. 117 // 3. If currently a gc is running, ConcurrentMarkThread will wait it to be finished. 118 // And then sleep for predicted amount of time by delay_to_keep_mmu(). 119 SuspendibleThreadSetJoiner sts_join; 120 121 const G1Analytics* analytics = g1_policy->analytics(); 122 double now = os::elapsedTime(); 123 double prediction_ms = remark ? analytics->predict_remark_time_ms() 124 : analytics->predict_cleanup_time_ms(); 125 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker(); 126 return mmu_tracker->when_ms(now, prediction_ms); 127 } 128 129 void G1ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) { 130 if (g1_policy->adaptive_young_list_length()) { 131 jlong sleep_time_ms = mmu_sleep_time(g1_policy, remark); 132 if (!_cm->has_aborted() && sleep_time_ms > 0) { 133 os::sleep(this, sleep_time_ms, false); 134 } 135 } 136 } 137 138 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> { 139 G1ConcurrentMark* _cm; 140 141 public: 142 G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) : 143 GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title), 144 _cm(cm) 145 { 146 _cm->gc_timer_cm()->register_gc_concurrent_start(title); 147 } 148 149 ~G1ConcPhaseTimer() { 150 _cm->gc_timer_cm()->register_gc_concurrent_end(); 151 } 152 }; 153 154 static const char* const concurrent_phase_names[] = { 155 #define CONCURRENT_PHASE_NAME(tag, ignore_value, ignore_title) XSTR(tag), 156 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_NAME) 157 #undef CONCURRENT_PHASE_NAME 158 NULL // terminator 159 }; 160 // Verify dense enum assumption. +1 for terminator. 161 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT + 1 == 162 ARRAY_SIZE(concurrent_phase_names)); 163 164 // Returns the phase number for name, or a negative value if unknown. 165 static int lookup_concurrent_phase(const char* name) { 166 const char* const* names = concurrent_phase_names; 167 for (uint i = 0; names[i] != NULL; ++i) { 168 if (strcmp(name, names[i]) == 0) { 169 return static_cast<int>(i); 170 } 171 } 172 return -1; 173 } 174 175 // The phase must be valid and must have a title. 176 static const char* lookup_concurrent_phase_title(int phase) { 177 static const char* const titles[] = { 178 #define CONCURRENT_PHASE_TITLE(ignore_tag, ignore_value, title) title, 179 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_TITLE) 180 #undef CONCURRENT_PHASE_TITLE 181 }; 182 // Verify dense enum assumption. 183 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT == ARRAY_SIZE(titles)); 184 185 assert(0 <= phase, "precondition"); 186 assert((uint)phase < ARRAY_SIZE(titles), "precondition"); 187 const char* title = titles[phase]; 188 assert(title != NULL, "precondition"); 189 return title; 190 } 191 192 class G1ConcPhaseManager : public StackObj { 193 G1ConcurrentMark* _cm; 194 ConcurrentGCPhaseManager _manager; 195 196 public: 197 G1ConcPhaseManager(int phase, G1ConcurrentMarkThread* thread) : 198 _cm(thread->cm()), 199 _manager(phase, thread->phase_manager_stack()) 200 { } 201 202 ~G1ConcPhaseManager() { 203 // Deactivate the manager if marking aborted, to avoid blocking on 204 // phase exit when the phase has been requested. 205 if (_cm->has_aborted()) { 206 _manager.deactivate(); 207 } 208 } 209 210 void set_phase(int phase, bool force) { 211 _manager.set_phase(phase, force); 212 } 213 }; 214 215 // Combine phase management and timing into one convenient utility. 216 class G1ConcPhase : public StackObj { 217 G1ConcPhaseTimer _timer; 218 G1ConcPhaseManager _manager; 219 220 public: 221 G1ConcPhase(int phase, G1ConcurrentMarkThread* thread) : 222 _timer(thread->cm(), lookup_concurrent_phase_title(phase)), 223 _manager(phase, thread) 224 { } 225 }; 226 227 const char* const* G1ConcurrentMarkThread::concurrent_phases() const { 228 return concurrent_phase_names; 229 } 230 231 bool G1ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) { 232 int phase = lookup_concurrent_phase(phase_name); 233 if (phase < 0) return false; 234 235 while (!ConcurrentGCPhaseManager::wait_for_phase(phase, 236 phase_manager_stack())) { 237 assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed"); 238 if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) { 239 // If idle and the goal is !idle, start a collection. 240 G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark); 241 } 242 } 243 return true; 244 } 245 246 void G1ConcurrentMarkThread::run_service() { 247 _vtime_start = os::elapsedVTime(); 248 249 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 250 G1Policy* g1_policy = g1h->g1_policy(); 251 252 G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this); 253 254 while (!should_terminate()) { 255 // wait until started is set. 256 sleep_before_next_cycle(); 257 if (should_terminate()) { 258 break; 259 } 260 261 cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */); 262 263 GCIdMark gc_id_mark; 264 265 _cm->concurrent_cycle_start(); 266 267 GCTraceConcTime(Info, gc) tt("Concurrent Cycle"); 268 { 269 ResourceMark rm; 270 HandleMark hm; 271 double cycle_start = os::elapsedVTime(); 272 273 { 274 G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this); 275 ClassLoaderDataGraph::clear_claimed_marks(); 276 } 277 278 // We have to ensure that we finish scanning the root regions 279 // before the next GC takes place. To ensure this we have to 280 // make sure that we do not join the STS until the root regions 281 // have been scanned. If we did then it's possible that a 282 // subsequent GC could block us from joining the STS and proceed 283 // without the root regions have been scanned which would be a 284 // correctness issue. 285 286 { 287 G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this); 288 _cm->scan_root_regions(); 289 } 290 291 // It would be nice to use the G1ConcPhase class here but 292 // the "end" logging is inside the loop and not at the end of 293 // a scope. Also, the timer doesn't support nesting. 294 // Mimicking the same log output instead. 295 { 296 G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this); 297 jlong mark_start = os::elapsed_counter(); 298 const char* cm_title = lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK); 299 log_info(gc, marking)("%s (%.3fs)", 300 cm_title, 301 TimeHelper::counter_to_seconds(mark_start)); 302 for (uint iter = 1; !_cm->has_aborted(); ++iter) { 303 // Concurrent marking. 304 { 305 G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this); 306 _cm->mark_from_roots(); 307 } 308 if (_cm->has_aborted()) { 309 break; 310 } 311 312 // Provide a control point after mark_from_roots. 313 { 314 G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this); 315 } 316 if (_cm->has_aborted()) { 317 break; 318 } 319 320 // Delay remark pause for MMU. 321 double mark_end_time = os::elapsedVTime(); 322 jlong mark_end = os::elapsed_counter(); 323 _vtime_mark_accum += (mark_end_time - cycle_start); 324 delay_to_keep_mmu(g1_policy, true /* remark */); 325 if (_cm->has_aborted()) { 326 break; 327 } 328 329 // Pause Remark. 330 log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms", 331 cm_title, 332 TimeHelper::counter_to_seconds(mark_start), 333 TimeHelper::counter_to_seconds(mark_end), 334 TimeHelper::counter_to_millis(mark_end - mark_start)); 335 mark_manager.set_phase(G1ConcurrentPhase::REMARK, false); 336 CMRemark cl(_cm); 337 VM_CGC_Operation op(&cl, "Pause Remark"); 338 VMThread::execute(&op); 339 if (_cm->has_aborted()) { 340 break; 341 } else if (!_cm->restart_for_overflow()) { 342 break; // Exit loop if no restart requested. 343 } else { 344 // Loop to restart for overflow. 345 mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false); 346 log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)", 347 cm_title, iter); 348 } 349 } 350 } 351 352 if (!_cm->has_aborted()) { 353 G1ConcPhase p(G1ConcurrentPhase::REBUILD_REMEMBERED_SETS, this); 354 _cm->rebuild_rem_set_concurrently(); 355 } 356 357 double end_time = os::elapsedVTime(); 358 // Update the total virtual time before doing this, since it will try 359 // to measure it to get the vtime for this marking. 360 _vtime_accum = (end_time - _vtime_start); 361 362 if (!_cm->has_aborted()) { 363 delay_to_keep_mmu(g1_policy, false /* cleanup */); 364 } 365 366 if (!_cm->has_aborted()) { 367 CMCleanup cl_cl(_cm); 368 VM_CGC_Operation op(&cl_cl, "Pause Cleanup"); 369 VMThread::execute(&op); 370 } 371 372 // We now want to allow clearing of the marking bitmap to be 373 // suspended by a collection pause. 374 // We may have aborted just before the remark. Do not bother clearing the 375 // bitmap then, as it has been done during mark abort. 376 if (!_cm->has_aborted()) { 377 G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this); 378 _cm->cleanup_for_next_mark(); 379 } else { 380 assert(!G1VerifyBitmaps || _cm->next_mark_bitmap_is_clear(), "Next mark bitmap must be clear"); 381 } 382 } 383 384 // Update the number of full collections that have been 385 // completed. This will also notify the FullGCCount_lock in case a 386 // Java thread is waiting for a full GC to happen (e.g., it 387 // called System.gc() with +ExplicitGCInvokesConcurrent). 388 { 389 SuspendibleThreadSetJoiner sts_join; 390 g1h->increment_old_marking_cycles_completed(true /* concurrent */); 391 392 _cm->concurrent_cycle_end(); 393 } 394 395 cpmanager.set_phase(G1ConcurrentPhase::IDLE, _cm->has_aborted() /* force */); 396 } 397 _cm->root_regions()->cancel_scan(); 398 } 399 400 void G1ConcurrentMarkThread::stop_service() { 401 MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag); 402 CGC_lock->notify_all(); 403 } 404 405 406 void G1ConcurrentMarkThread::sleep_before_next_cycle() { 407 // We join here because we don't want to do the "shouldConcurrentMark()" 408 // below while the world is otherwise stopped. 409 assert(!in_progress(), "should have been cleared"); 410 411 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 412 while (!started() && !should_terminate()) { 413 CGC_lock->wait(Mutex::_no_safepoint_check_flag); 414 } 415 416 if (started()) { 417 set_in_progress(); 418 } 419 }