1/* 2 * Copyright (c) 2001, 2017, 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/concurrentMarkThread.inline.hpp" 28#include "gc/g1/g1Analytics.hpp" 29#include "gc/g1/g1CollectedHeap.inline.hpp" 30#include "gc/g1/g1ConcurrentMark.inline.hpp" 31#include "gc/g1/g1MMUTracker.hpp" 32#include "gc/g1/g1Policy.hpp" 33#include "gc/g1/suspendibleThreadSet.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 "logging/log.hpp" 40#include "memory/resourceArea.hpp" 41#include "runtime/vmThread.hpp" 42#include "utilities/debug.hpp" 43 44// ======= Concurrent Mark Thread ======== 45 46// Check order in EXPAND_CURRENT_PHASES 47STATIC_ASSERT(ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE < 48 ConcurrentGCPhaseManager::IDLE_PHASE); 49 50#define EXPAND_CONCURRENT_PHASES(expander) \ 51 expander(ANY, = ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE, NULL) \ 52 expander(IDLE, = ConcurrentGCPhaseManager::IDLE_PHASE, NULL) \ 53 expander(CONCURRENT_CYCLE,, "Concurrent Cycle") \ 54 expander(CLEAR_CLAIMED_MARKS,, "Concurrent Clear Claimed Marks") \ 55 expander(SCAN_ROOT_REGIONS,, "Concurrent Scan Root Regions") \ 56 expander(CONCURRENT_MARK,, "Concurrent Mark") \ 57 expander(MARK_FROM_ROOTS,, "Concurrent Mark From Roots") \ 58 expander(BEFORE_REMARK,, NULL) \ 59 expander(REMARK,, NULL) \ 60 expander(CREATE_LIVE_DATA,, "Concurrent Create Live Data") \ 61 expander(COMPLETE_CLEANUP,, "Concurrent Complete Cleanup") \ 62 expander(CLEANUP_FOR_NEXT_MARK,, "Concurrent Cleanup for Next Mark") \ 63 /* */ 64 65class G1ConcurrentPhase : public AllStatic { 66public: 67 enum { 68#define CONCURRENT_PHASE_ENUM(tag, value, ignore_title) tag value, 69 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_ENUM) 70#undef CONCURRENT_PHASE_ENUM 71 PHASE_ID_LIMIT 72 }; 73}; 74 75// The CM thread is created when the G1 garbage collector is used 76 77ConcurrentMarkThread::ConcurrentMarkThread(G1ConcurrentMark* cm) : 78 ConcurrentGCThread(), 79 _cm(cm), 80 _state(Idle), 81 _phase_manager_stack(), 82 _vtime_accum(0.0), 83 _vtime_mark_accum(0.0) { 84 85 set_name("G1 Main Marker"); 86 create_and_start(); 87} 88 89class CMCheckpointRootsFinalClosure: public VoidClosure { 90 91 G1ConcurrentMark* _cm; 92public: 93 94 CMCheckpointRootsFinalClosure(G1ConcurrentMark* cm) : 95 _cm(cm) {} 96 97 void do_void(){ 98 _cm->checkpointRootsFinal(false); // !clear_all_soft_refs 99 } 100}; 101 102class CMCleanUp: public VoidClosure { 103 G1ConcurrentMark* _cm; 104public: 105 106 CMCleanUp(G1ConcurrentMark* cm) : 107 _cm(cm) {} 108 109 void do_void(){ 110 _cm->cleanup(); 111 } 112}; 113 114// Marking pauses can be scheduled flexibly, so we might delay marking to meet MMU. 115void ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) { 116 const G1Analytics* analytics = g1_policy->analytics(); 117 if (g1_policy->adaptive_young_list_length()) { 118 double now = os::elapsedTime(); 119 double prediction_ms = remark ? analytics->predict_remark_time_ms() 120 : analytics->predict_cleanup_time_ms(); 121 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker(); 122 jlong sleep_time_ms = mmu_tracker->when_ms(now, prediction_ms); 123 os::sleep(this, sleep_time_ms, false); 124 } 125} 126 127class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> { 128 G1ConcurrentMark* _cm; 129 130 public: 131 G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) : 132 GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title), 133 _cm(cm) 134 { 135 _cm->gc_timer_cm()->register_gc_concurrent_start(title); 136 } 137 138 ~G1ConcPhaseTimer() { 139 _cm->gc_timer_cm()->register_gc_concurrent_end(); 140 } 141}; 142 143static const char* const concurrent_phase_names[] = { 144#define CONCURRENT_PHASE_NAME(tag, ignore_value, ignore_title) XSTR(tag), 145 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_NAME) 146#undef CONCURRENT_PHASE_NAME 147 NULL // terminator 148}; 149// Verify dense enum assumption. +1 for terminator. 150STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT + 1 == 151 ARRAY_SIZE(concurrent_phase_names)); 152 153// Returns the phase number for name, or a negative value if unknown. 154static int lookup_concurrent_phase(const char* name) { 155 const char* const* names = concurrent_phase_names; 156 for (uint i = 0; names[i] != NULL; ++i) { 157 if (strcmp(name, names[i]) == 0) { 158 return static_cast<int>(i); 159 } 160 } 161 return -1; 162} 163 164// The phase must be valid and must have a title. 165static const char* lookup_concurrent_phase_title(int phase) { 166 static const char* const titles[] = { 167#define CONCURRENT_PHASE_TITLE(ignore_tag, ignore_value, title) title, 168 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_TITLE) 169#undef CONCURRENT_PHASE_TITLE 170 }; 171 // Verify dense enum assumption. 172 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT == ARRAY_SIZE(titles)); 173 174 assert(0 <= phase, "precondition"); 175 assert((uint)phase < ARRAY_SIZE(titles), "precondition"); 176 const char* title = titles[phase]; 177 assert(title != NULL, "precondition"); 178 return title; 179} 180 181class G1ConcPhaseManager : public StackObj { 182 G1ConcurrentMark* _cm; 183 ConcurrentGCPhaseManager _manager; 184 185public: 186 G1ConcPhaseManager(int phase, ConcurrentMarkThread* thread) : 187 _cm(thread->cm()), 188 _manager(phase, thread->phase_manager_stack()) 189 { } 190 191 ~G1ConcPhaseManager() { 192 // Deactivate the manager if marking aborted, to avoid blocking on 193 // phase exit when the phase has been requested. 194 if (_cm->has_aborted()) { 195 _manager.deactivate(); 196 } 197 } 198 199 void set_phase(int phase, bool force) { 200 _manager.set_phase(phase, force); 201 } 202}; 203 204// Combine phase management and timing into one convenient utility. 205class G1ConcPhase : public StackObj { 206 G1ConcPhaseTimer _timer; 207 G1ConcPhaseManager _manager; 208 209public: 210 G1ConcPhase(int phase, ConcurrentMarkThread* thread) : 211 _timer(thread->cm(), lookup_concurrent_phase_title(phase)), 212 _manager(phase, thread) 213 { } 214}; 215 216const char* const* ConcurrentMarkThread::concurrent_phases() const { 217 return concurrent_phase_names; 218} 219 220bool ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) { 221 int phase = lookup_concurrent_phase(phase_name); 222 if (phase < 0) return false; 223 224 while (!ConcurrentGCPhaseManager::wait_for_phase(phase, 225 phase_manager_stack())) { 226 assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed"); 227 if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) { 228 // If idle and the goal is !idle, start a collection. 229 G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark); 230 } 231 } 232 return true; 233} 234 235void ConcurrentMarkThread::run_service() { 236 _vtime_start = os::elapsedVTime(); 237 238 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 239 G1Policy* g1_policy = g1h->g1_policy(); 240 241 G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this); 242 243 while (!should_terminate()) { 244 // wait until started is set. 245 sleepBeforeNextCycle(); 246 if (should_terminate()) { 247 break; 248 } 249 250 cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */); 251 252 GCIdMark gc_id_mark; 253 254 cm()->concurrent_cycle_start(); 255 256 assert(GCId::current() != GCId::undefined(), "GC id should have been set up by the initial mark GC."); 257 258 GCTraceConcTime(Info, gc) tt("Concurrent Cycle"); 259 { 260 ResourceMark rm; 261 HandleMark hm; 262 double cycle_start = os::elapsedVTime(); 263 264 { 265 G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this); 266 ClassLoaderDataGraph::clear_claimed_marks(); 267 } 268 269 // We have to ensure that we finish scanning the root regions 270 // before the next GC takes place. To ensure this we have to 271 // make sure that we do not join the STS until the root regions 272 // have been scanned. If we did then it's possible that a 273 // subsequent GC could block us from joining the STS and proceed 274 // without the root regions have been scanned which would be a 275 // correctness issue. 276 277 { 278 G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this); 279 _cm->scan_root_regions(); 280 } 281 282 // It would be nice to use the G1ConcPhase class here but 283 // the "end" logging is inside the loop and not at the end of 284 // a scope. Also, the timer doesn't support nesting. 285 // Mimicking the same log output instead. 286 { 287 G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this); 288 jlong mark_start = os::elapsed_counter(); 289 const char* cm_title = 290 lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK); 291 log_info(gc, marking)("%s (%.3fs)", 292 cm_title, 293 TimeHelper::counter_to_seconds(mark_start)); 294 for (uint iter = 1; !cm()->has_aborted(); ++iter) { 295 // Concurrent marking. 296 { 297 G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this); 298 _cm->mark_from_roots(); 299 } 300 if (cm()->has_aborted()) break; 301 302 // Provide a control point after mark_from_roots. 303 { 304 G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this); 305 } 306 if (cm()->has_aborted()) break; 307 308 // Delay remark pause for MMU. 309 double mark_end_time = os::elapsedVTime(); 310 jlong mark_end = os::elapsed_counter(); 311 _vtime_mark_accum += (mark_end_time - cycle_start); 312 delay_to_keep_mmu(g1_policy, true /* remark */); 313 if (cm()->has_aborted()) break; 314 315 // Pause Remark. 316 log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms", 317 cm_title, 318 TimeHelper::counter_to_seconds(mark_start), 319 TimeHelper::counter_to_seconds(mark_end), 320 TimeHelper::counter_to_millis(mark_end - mark_start)); 321 mark_manager.set_phase(G1ConcurrentPhase::REMARK, false); 322 CMCheckpointRootsFinalClosure final_cl(_cm); 323 VM_CGC_Operation op(&final_cl, "Pause Remark"); 324 VMThread::execute(&op); 325 if (cm()->has_aborted()) { 326 break; 327 } else if (!cm()->restart_for_overflow()) { 328 break; // Exit loop if no restart requested. 329 } else { 330 // Loop to restart for overflow. 331 mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false); 332 log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)", 333 cm_title, iter); 334 } 335 } 336 } 337 338 if (!cm()->has_aborted()) { 339 G1ConcPhase p(G1ConcurrentPhase::CREATE_LIVE_DATA, this); 340 cm()->create_live_data(); 341 } 342 343 double end_time = os::elapsedVTime(); 344 // Update the total virtual time before doing this, since it will try 345 // to measure it to get the vtime for this marking. We purposely 346 // neglect the presumably-short "completeCleanup" phase here. 347 _vtime_accum = (end_time - _vtime_start); 348 349 if (!cm()->has_aborted()) { 350 delay_to_keep_mmu(g1_policy, false /* cleanup */); 351 352 CMCleanUp cl_cl(_cm); 353 VM_CGC_Operation op(&cl_cl, "Pause Cleanup"); 354 VMThread::execute(&op); 355 } else { 356 // We don't want to update the marking status if a GC pause 357 // is already underway. 358 SuspendibleThreadSetJoiner sts_join; 359 g1h->collector_state()->set_mark_in_progress(false); 360 } 361 362 // Check if cleanup set the free_regions_coming flag. If it 363 // hasn't, we can just skip the next step. 364 if (g1h->free_regions_coming()) { 365 // The following will finish freeing up any regions that we 366 // found to be empty during cleanup. We'll do this part 367 // without joining the suspendible set. If an evacuation pause 368 // takes place, then we would carry on freeing regions in 369 // case they are needed by the pause. If a Full GC takes 370 // place, it would wait for us to process the regions 371 // reclaimed by cleanup. 372 373 // Now do the concurrent cleanup operation. 374 G1ConcPhase p(G1ConcurrentPhase::COMPLETE_CLEANUP, this); 375 _cm->complete_cleanup(); 376 377 // Notify anyone who's waiting that there are no more free 378 // regions coming. We have to do this before we join the STS 379 // (in fact, we should not attempt to join the STS in the 380 // interval between finishing the cleanup pause and clearing 381 // the free_regions_coming flag) otherwise we might deadlock: 382 // a GC worker could be blocked waiting for the notification 383 // whereas this thread will be blocked for the pause to finish 384 // while it's trying to join the STS, which is conditional on 385 // the GC workers finishing. 386 g1h->reset_free_regions_coming(); 387 } 388 guarantee(cm()->cleanup_list_is_empty(), 389 "at this point there should be no regions on the cleanup list"); 390 391 // There is a tricky race before recording that the concurrent 392 // cleanup has completed and a potential Full GC starting around 393 // the same time. We want to make sure that the Full GC calls 394 // abort() on concurrent mark after 395 // record_concurrent_mark_cleanup_completed(), since abort() is 396 // the method that will reset the concurrent mark state. If we 397 // end up calling record_concurrent_mark_cleanup_completed() 398 // after abort() then we might incorrectly undo some of the work 399 // abort() did. Checking the has_aborted() flag after joining 400 // the STS allows the correct ordering of the two methods. There 401 // are two scenarios: 402 // 403 // a) If we reach here before the Full GC, the fact that we have 404 // joined the STS means that the Full GC cannot start until we 405 // leave the STS, so record_concurrent_mark_cleanup_completed() 406 // will complete before abort() is called. 407 // 408 // b) If we reach here during the Full GC, we'll be held up from 409 // joining the STS until the Full GC is done, which means that 410 // abort() will have completed and has_aborted() will return 411 // true to prevent us from calling 412 // record_concurrent_mark_cleanup_completed() (and, in fact, it's 413 // not needed any more as the concurrent mark state has been 414 // already reset). 415 { 416 SuspendibleThreadSetJoiner sts_join; 417 if (!cm()->has_aborted()) { 418 g1_policy->record_concurrent_mark_cleanup_completed(); 419 } else { 420 log_info(gc, marking)("Concurrent Mark Abort"); 421 } 422 } 423 424 // We now want to allow clearing of the marking bitmap to be 425 // suspended by a collection pause. 426 // We may have aborted just before the remark. Do not bother clearing the 427 // bitmap then, as it has been done during mark abort. 428 if (!cm()->has_aborted()) { 429 G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this); 430 _cm->cleanup_for_next_mark(); 431 } else { 432 assert(!G1VerifyBitmaps || _cm->nextMarkBitmapIsClear(), "Next mark bitmap must be clear"); 433 } 434 } 435 436 // Update the number of full collections that have been 437 // completed. This will also notify the FullGCCount_lock in case a 438 // Java thread is waiting for a full GC to happen (e.g., it 439 // called System.gc() with +ExplicitGCInvokesConcurrent). 440 { 441 SuspendibleThreadSetJoiner sts_join; 442 g1h->increment_old_marking_cycles_completed(true /* concurrent */); 443 444 cm()->concurrent_cycle_end(); 445 } 446 447 cpmanager.set_phase(G1ConcurrentPhase::IDLE, cm()->has_aborted() /* force */); 448 } 449 _cm->root_regions()->cancel_scan(); 450} 451 452void ConcurrentMarkThread::stop_service() { 453 MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag); 454 CGC_lock->notify_all(); 455} 456 457void ConcurrentMarkThread::sleepBeforeNextCycle() { 458 // We join here because we don't want to do the "shouldConcurrentMark()" 459 // below while the world is otherwise stopped. 460 assert(!in_progress(), "should have been cleared"); 461 462 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 463 while (!started() && !should_terminate()) { 464 CGC_lock->wait(Mutex::_no_safepoint_check_flag); 465 } 466 467 if (started()) { 468 set_in_progress(); 469 } 470} 471