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(PRECLEAN,, "Concurrent Preclean")                               \
  61   expander(BEFORE_REMARK,, NULL)                                           \
  62   expander(REMARK,, NULL)                                                  \
  63   expander(REBUILD_REMEMBERED_SETS,, "Concurrent Rebuild Remembered Sets") \
  64   expander(CLEANUP_FOR_NEXT_MARK,, "Concurrent Cleanup for Next Mark")     \
  65   /* */
  66 
  67 class G1ConcurrentPhase : public AllStatic {
  68 public:
  69   enum {
  70 #define CONCURRENT_PHASE_ENUM(tag, value, ignore_title) tag value,
  71     EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_ENUM)
  72 #undef CONCURRENT_PHASE_ENUM
  73     PHASE_ID_LIMIT
  74   };
  75 };
  76 
  77 // The CM thread is created when the G1 garbage collector is used
  78 
  79 G1ConcurrentMarkThread::G1ConcurrentMarkThread(G1ConcurrentMark* cm) :
  80   ConcurrentGCThread(),
  81   _cm(cm),
  82   _state(Idle),
  83   _phase_manager_stack(),
  84   _vtime_accum(0.0),
  85   _vtime_mark_accum(0.0) {
  86 
  87   set_name("G1 Main Marker");
  88   create_and_start();
  89 }
  90 
  91 class CMRemark : public VoidClosure {
  92   G1ConcurrentMark* _cm;
  93 public:
  94   CMRemark(G1ConcurrentMark* cm) : _cm(cm) {}
  95 
  96   void do_void(){
  97     _cm->remark();
  98   }
  99 };
 100 
 101 class CMCleanup : public VoidClosure {
 102   G1ConcurrentMark* _cm;
 103 public:
 104   CMCleanup(G1ConcurrentMark* cm) : _cm(cm) {}
 105 
 106   void do_void(){
 107     _cm->cleanup();
 108   }
 109 };
 110 
 111 double G1ConcurrentMarkThread::mmu_sleep_time(G1Policy* g1_policy, bool remark) {
 112   // There are 3 reasons to use SuspendibleThreadSetJoiner.
 113   // 1. To avoid concurrency problem.
 114   //    - G1MMUTracker::add_pause(), when_sec() and its variation(when_ms() etc..) can be called
 115   //      concurrently from ConcurrentMarkThread and VMThread.
 116   // 2. If currently a gc is running, but it has not yet updated the MMU,
 117   //    we will not forget to consider that pause in the MMU calculation.
 118   // 3. If currently a gc is running, ConcurrentMarkThread will wait it to be finished.
 119   //    And then sleep for predicted amount of time by delay_to_keep_mmu().
 120   SuspendibleThreadSetJoiner sts_join;
 121 
 122   const G1Analytics* analytics = g1_policy->analytics();
 123   double now = os::elapsedTime();
 124   double prediction_ms = remark ? analytics->predict_remark_time_ms()
 125                                 : analytics->predict_cleanup_time_ms();
 126   G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
 127   return mmu_tracker->when_ms(now, prediction_ms);
 128 }
 129 
 130 void G1ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) {
 131   if (g1_policy->adaptive_young_list_length()) {
 132     jlong sleep_time_ms = mmu_sleep_time(g1_policy, remark);
 133     if (!_cm->has_aborted() && sleep_time_ms > 0) {
 134       os::sleep(this, sleep_time_ms, false);
 135     }
 136   }
 137 }
 138 
 139 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
 140   G1ConcurrentMark* _cm;
 141 
 142  public:
 143   G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
 144     GCTraceConcTimeImpl<LogLevel::Info,  LogTag::_gc, LogTag::_marking>(title),
 145     _cm(cm)
 146   {
 147     _cm->gc_timer_cm()->register_gc_concurrent_start(title);
 148   }
 149 
 150   ~G1ConcPhaseTimer() {
 151     _cm->gc_timer_cm()->register_gc_concurrent_end();
 152   }
 153 };
 154 
 155 static const char* const concurrent_phase_names[] = {
 156 #define CONCURRENT_PHASE_NAME(tag, ignore_value, ignore_title) XSTR(tag),
 157   EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_NAME)
 158 #undef CONCURRENT_PHASE_NAME
 159   NULL                          // terminator
 160 };
 161 // Verify dense enum assumption.  +1 for terminator.
 162 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT + 1 ==
 163               ARRAY_SIZE(concurrent_phase_names));
 164 
 165 // Returns the phase number for name, or a negative value if unknown.
 166 static int lookup_concurrent_phase(const char* name) {
 167   const char* const* names = concurrent_phase_names;
 168   for (uint i = 0; names[i] != NULL; ++i) {
 169     if (strcmp(name, names[i]) == 0) {
 170       return static_cast<int>(i);
 171     }
 172   }
 173   return -1;
 174 }
 175 
 176 // The phase must be valid and must have a title.
 177 static const char* lookup_concurrent_phase_title(int phase) {
 178   static const char* const titles[] = {
 179 #define CONCURRENT_PHASE_TITLE(ignore_tag, ignore_value, title) title,
 180     EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_TITLE)
 181 #undef CONCURRENT_PHASE_TITLE
 182   };
 183   // Verify dense enum assumption.
 184   STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT == ARRAY_SIZE(titles));
 185 
 186   assert(0 <= phase, "precondition");
 187   assert((uint)phase < ARRAY_SIZE(titles), "precondition");
 188   const char* title = titles[phase];
 189   assert(title != NULL, "precondition");
 190   return title;
 191 }
 192 
 193 class G1ConcPhaseManager : public StackObj {
 194   G1ConcurrentMark* _cm;
 195   ConcurrentGCPhaseManager _manager;
 196 
 197 public:
 198   G1ConcPhaseManager(int phase, G1ConcurrentMarkThread* thread) :
 199     _cm(thread->cm()),
 200     _manager(phase, thread->phase_manager_stack())
 201   { }
 202 
 203   ~G1ConcPhaseManager() {
 204     // Deactivate the manager if marking aborted, to avoid blocking on
 205     // phase exit when the phase has been requested.
 206     if (_cm->has_aborted()) {
 207       _manager.deactivate();
 208     }
 209   }
 210 
 211   void set_phase(int phase, bool force) {
 212     _manager.set_phase(phase, force);
 213   }
 214 };
 215 
 216 // Combine phase management and timing into one convenient utility.
 217 class G1ConcPhase : public StackObj {
 218   G1ConcPhaseTimer _timer;
 219   G1ConcPhaseManager _manager;
 220 
 221 public:
 222   G1ConcPhase(int phase, G1ConcurrentMarkThread* thread) :
 223     _timer(thread->cm(), lookup_concurrent_phase_title(phase)),
 224     _manager(phase, thread)
 225   { }
 226 };
 227 
 228 const char* const* G1ConcurrentMarkThread::concurrent_phases() const {
 229   return concurrent_phase_names;
 230 }
 231 
 232 bool G1ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) {
 233   int phase = lookup_concurrent_phase(phase_name);
 234   if (phase < 0) return false;
 235 
 236   while (!ConcurrentGCPhaseManager::wait_for_phase(phase,
 237                                                    phase_manager_stack())) {
 238     assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed");
 239     if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) {
 240       // If idle and the goal is !idle, start a collection.
 241       G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark);
 242     }
 243   }
 244   return true;
 245 }
 246 
 247 void G1ConcurrentMarkThread::run_service() {
 248   _vtime_start = os::elapsedVTime();
 249 
 250   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 251   G1Policy* g1_policy = g1h->g1_policy();
 252 
 253   G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this);
 254 
 255   while (!should_terminate()) {
 256     // wait until started is set.
 257     sleep_before_next_cycle();
 258     if (should_terminate()) {
 259       break;
 260     }
 261 
 262     cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */);
 263 
 264     GCIdMark gc_id_mark;
 265 
 266     _cm->concurrent_cycle_start();
 267 
 268     GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
 269     {
 270       ResourceMark rm;
 271       HandleMark   hm;
 272       double cycle_start = os::elapsedVTime();
 273 
 274       {
 275         G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this);
 276         ClassLoaderDataGraph::clear_claimed_marks();
 277       }
 278 
 279       // We have to ensure that we finish scanning the root regions
 280       // before the next GC takes place. To ensure this we have to
 281       // make sure that we do not join the STS until the root regions
 282       // have been scanned. If we did then it's possible that a
 283       // subsequent GC could block us from joining the STS and proceed
 284       // without the root regions have been scanned which would be a
 285       // correctness issue.
 286 
 287       {
 288         G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this);
 289         _cm->scan_root_regions();
 290       }
 291 
 292       // It would be nice to use the G1ConcPhase class here but
 293       // the "end" logging is inside the loop and not at the end of
 294       // a scope. Also, the timer doesn't support nesting.
 295       // Mimicking the same log output instead.
 296       {
 297         G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this);
 298         jlong mark_start = os::elapsed_counter();
 299         const char* cm_title = lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK);
 300         log_info(gc, marking)("%s (%.3fs)",
 301                               cm_title,
 302                               TimeHelper::counter_to_seconds(mark_start));
 303         for (uint iter = 1; !_cm->has_aborted(); ++iter) {
 304           // Concurrent marking.
 305           {
 306             G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this);
 307             _cm->mark_from_roots();
 308           }
 309           if (_cm->has_aborted()) {
 310             break;
 311           }
 312 
 313           if (G1UseReferencePrecleaning) {
 314             G1ConcPhase p(G1ConcurrentPhase::PRECLEAN, this);
 315             _cm->preclean();
 316           }
 317 
 318           // Provide a control point before remark.
 319           {
 320             G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this);
 321           }
 322           if (_cm->has_aborted()) {
 323             break;
 324           }
 325 
 326           // Delay remark pause for MMU.
 327           double mark_end_time = os::elapsedVTime();
 328           jlong mark_end = os::elapsed_counter();
 329           _vtime_mark_accum += (mark_end_time - cycle_start);
 330           delay_to_keep_mmu(g1_policy, true /* remark */);
 331           if (_cm->has_aborted()) {
 332             break;
 333           }
 334 
 335           // Pause Remark.
 336           log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms",
 337                                 cm_title,
 338                                 TimeHelper::counter_to_seconds(mark_start),
 339                                 TimeHelper::counter_to_seconds(mark_end),
 340                                 TimeHelper::counter_to_millis(mark_end - mark_start));
 341           mark_manager.set_phase(G1ConcurrentPhase::REMARK, false);
 342           CMRemark cl(_cm);
 343           VM_CGC_Operation op(&cl, "Pause Remark");
 344           VMThread::execute(&op);
 345           if (_cm->has_aborted()) {
 346             break;
 347           } else if (!_cm->restart_for_overflow()) {
 348             break;              // Exit loop if no restart requested.
 349           } else {
 350             // Loop to restart for overflow.
 351             mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false);
 352             log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)",
 353                                   cm_title, iter);
 354           }
 355         }
 356       }
 357 
 358       if (!_cm->has_aborted()) {
 359         G1ConcPhase p(G1ConcurrentPhase::REBUILD_REMEMBERED_SETS, this);
 360         _cm->rebuild_rem_set_concurrently();
 361       }
 362 
 363       double end_time = os::elapsedVTime();
 364       // Update the total virtual time before doing this, since it will try
 365       // to measure it to get the vtime for this marking.
 366       _vtime_accum = (end_time - _vtime_start);
 367 
 368       if (!_cm->has_aborted()) {
 369         delay_to_keep_mmu(g1_policy, false /* cleanup */);
 370       }
 371 
 372       if (!_cm->has_aborted()) {
 373         CMCleanup cl_cl(_cm);
 374         VM_CGC_Operation op(&cl_cl, "Pause Cleanup");
 375         VMThread::execute(&op);
 376       }
 377 
 378       // We now want to allow clearing of the marking bitmap to be
 379       // suspended by a collection pause.
 380       // We may have aborted just before the remark. Do not bother clearing the
 381       // bitmap then, as it has been done during mark abort.
 382       if (!_cm->has_aborted()) {
 383         G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this);
 384         _cm->cleanup_for_next_mark();
 385       } else {
 386         assert(!G1VerifyBitmaps || _cm->next_mark_bitmap_is_clear(), "Next mark bitmap must be clear");
 387       }
 388     }
 389 
 390     // Update the number of full collections that have been
 391     // completed. This will also notify the FullGCCount_lock in case a
 392     // Java thread is waiting for a full GC to happen (e.g., it
 393     // called System.gc() with +ExplicitGCInvokesConcurrent).
 394     {
 395       SuspendibleThreadSetJoiner sts_join;
 396       g1h->increment_old_marking_cycles_completed(true /* concurrent */);
 397 
 398       _cm->concurrent_cycle_end();
 399     }
 400 
 401     cpmanager.set_phase(G1ConcurrentPhase::IDLE, _cm->has_aborted() /* force */);
 402   }
 403   _cm->root_regions()->cancel_scan();
 404 }
 405 
 406 void G1ConcurrentMarkThread::stop_service() {
 407   MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag);
 408   CGC_lock->notify_all();
 409 }
 410 
 411 
 412 void G1ConcurrentMarkThread::sleep_before_next_cycle() {
 413   // We join here because we don't want to do the "shouldConcurrentMark()"
 414   // below while the world is otherwise stopped.
 415   assert(!in_progress(), "should have been cleared");
 416 
 417   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
 418   while (!started() && !should_terminate()) {
 419     CGC_lock->wait(Mutex::_no_safepoint_check_flag);
 420   }
 421 
 422   if (started()) {
 423     set_in_progress();
 424   }
 425 }