text: /*
   * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   *
   */
  
  #include "precompiled.hpp"
  #include "classfile/classLoaderDataGraph.hpp"
  #include "gc/g1/g1Analytics.hpp"
  #include "gc/g1/g1CollectedHeap.inline.hpp"
  #include "gc/g1/g1ConcurrentMark.inline.hpp"
  #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  #include "gc/g1/g1MMUTracker.hpp"
  #include "gc/g1/g1Policy.hpp"
  #include "gc/g1/g1RemSet.hpp"
  #include "gc/g1/g1VMOperations.hpp"
  #include "gc/shared/concurrentGCPhaseManager.hpp"
  #include "gc/shared/gcId.hpp"
  #include "gc/shared/gcTrace.hpp"
  #include "gc/shared/gcTraceTime.inline.hpp"
  #include "gc/shared/suspendibleThreadSet.hpp"
  #include "logging/log.hpp"
  #include "memory/resourceArea.hpp"
  #include "runtime/handles.inline.hpp"
  #include "runtime/vmThread.hpp"
  #include "utilities/debug.hpp"
  
  // ======= Concurrent Mark Thread ========
  
  // Check order in EXPAND_CURRENT_PHASES
  STATIC_ASSERT(ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE <
                ConcurrentGCPhaseManager::IDLE_PHASE);
  
  #define EXPAND_CONCURRENT_PHASES(expander)                                 \
    expander(ANY, = ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE, NULL)     \
    expander(IDLE, = ConcurrentGCPhaseManager::IDLE_PHASE, NULL)             \
    expander(CONCURRENT_CYCLE,, "Concurrent Cycle")                          \
    expander(CLEAR_CLAIMED_MARKS,, "Concurrent Clear Claimed Marks")         \
    expander(SCAN_ROOT_REGIONS,, "Concurrent Scan Root Regions")             \
    expander(CONCURRENT_MARK,, "Concurrent Mark")                            \
    expander(MARK_FROM_ROOTS,, "Concurrent Mark From Roots")                 \
    expander(PRECLEAN,, "Concurrent Preclean")                               \
    expander(BEFORE_REMARK,, NULL)                                           \
    expander(REMARK,, NULL)                                                  \
    expander(REBUILD_REMEMBERED_SETS,, "Concurrent Rebuild Remembered Sets") \
    expander(CLEANUP_FOR_NEXT_MARK,, "Concurrent Cleanup for Next Mark")     \
    /* */
  
  class G1ConcurrentPhase : public AllStatic {
  public:
    enum {
  #define CONCURRENT_PHASE_ENUM(tag, value, ignore_title) tag value,
      EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_ENUM)
  #undef CONCURRENT_PHASE_ENUM
      PHASE_ID_LIMIT
    };
  };
  
  G1ConcurrentMarkThread::G1ConcurrentMarkThread(G1ConcurrentMark* cm) :
    ConcurrentGCThread(),
    _vtime_start(0.0),
    _vtime_accum(0.0),
    _vtime_mark_accum(0.0),
    _cm(cm),
    _state(Idle),
    _phase_manager_stack() {
  
    set_name("G1 Main Marker");
    create_and_start();
  }
  
  class CMRemark : public VoidClosure {
    G1ConcurrentMark* _cm;
  public:
    CMRemark(G1ConcurrentMark* cm) : _cm(cm) {}
  
    void do_void(){
      _cm->remark();
    }
  };
  
  class CMCleanup : public VoidClosure {
    G1ConcurrentMark* _cm;
  public:
    CMCleanup(G1ConcurrentMark* cm) : _cm(cm) {}
  
    void do_void(){
      _cm->cleanup();
    }
  };
  
  double G1ConcurrentMarkThread::mmu_sleep_time(G1Policy* g1_policy, bool remark) {
    // There are 3 reasons to use SuspendibleThreadSetJoiner.
    // 1. To avoid concurrency problem.
    //    - G1MMUTracker::add_pause(), when_sec() and its variation(when_ms() etc..) can be called
    //      concurrently from ConcurrentMarkThread and VMThread.
    // 2. If currently a gc is running, but it has not yet updated the MMU,
    //    we will not forget to consider that pause in the MMU calculation.
    // 3. If currently a gc is running, ConcurrentMarkThread will wait it to be finished.
    //    And then sleep for predicted amount of time by delay_to_keep_mmu().
    SuspendibleThreadSetJoiner sts_join;
  
    const G1Analytics* analytics = g1_policy->analytics();
    double now = os::elapsedTime();
    double prediction_ms = remark ? analytics->predict_remark_time_ms()
                                  : analytics->predict_cleanup_time_ms();
    G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
    return mmu_tracker->when_ms(now, prediction_ms);
  }
  
  void G1ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) {
    if (g1_policy->use_adaptive_young_list_length()) {
      jlong sleep_time_ms = mmu_sleep_time(g1_policy, remark);
      if (!_cm->has_aborted() && sleep_time_ms > 0) {
        os::sleep(this, sleep_time_ms, false);
      }
    }
  }
  
  class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
    G1ConcurrentMark* _cm;
  
   public:
    G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
      GCTraceConcTimeImpl<LogLevel::Info,  LogTag::_gc, LogTag::_marking>(title),
      _cm(cm)
    {
      _cm->gc_timer_cm()->register_gc_concurrent_start(title);
    }
  
    ~G1ConcPhaseTimer() {
      _cm->gc_timer_cm()->register_gc_concurrent_end();
    }
  };
  
  static const char* const concurrent_phase_names[] = {
  #define CONCURRENT_PHASE_NAME(tag, ignore_value, ignore_title) XSTR(tag),
    EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_NAME)
  #undef CONCURRENT_PHASE_NAME
    NULL                          // terminator
  };
  // Verify dense enum assumption.  +1 for terminator.
  STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT + 1 ==
                ARRAY_SIZE(concurrent_phase_names));
  
  // Returns the phase number for name, or a negative value if unknown.
  static int lookup_concurrent_phase(const char* name) {
    const char* const* names = concurrent_phase_names;
    for (uint i = 0; names[i] != NULL; ++i) {
      if (strcmp(name, names[i]) == 0) {
        return static_cast<int>(i);
      }
    }
    return -1;
  }
  
  // The phase must be valid and must have a title.
  static const char* lookup_concurrent_phase_title(int phase) {
    static const char* const titles[] = {
  #define CONCURRENT_PHASE_TITLE(ignore_tag, ignore_value, title) title,
      EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_TITLE)
  #undef CONCURRENT_PHASE_TITLE
    };
    // Verify dense enum assumption.
    STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT == ARRAY_SIZE(titles));
  
    assert(0 <= phase, "precondition");
    assert((uint)phase < ARRAY_SIZE(titles), "precondition");
    const char* title = titles[phase];
    assert(title != NULL, "precondition");
    return title;
  }
  
  class G1ConcPhaseManager : public StackObj {
    G1ConcurrentMark* _cm;
    ConcurrentGCPhaseManager _manager;
  
  public:
    G1ConcPhaseManager(int phase, G1ConcurrentMarkThread* thread) :
      _cm(thread->cm()),
      _manager(phase, thread->phase_manager_stack())
    { }
  
    ~G1ConcPhaseManager() {
      // Deactivate the manager if marking aborted, to avoid blocking on
      // phase exit when the phase has been requested.
      if (_cm->has_aborted()) {
        _manager.deactivate();
      }
    }
  
    void set_phase(int phase, bool force) {
      _manager.set_phase(phase, force);
    }
  };
  
  // Combine phase management and timing into one convenient utility.
  class G1ConcPhase : public StackObj {
    G1ConcPhaseTimer _timer;
    G1ConcPhaseManager _manager;
  
  public:
    G1ConcPhase(int phase, G1ConcurrentMarkThread* thread) :
      _timer(thread->cm(), lookup_concurrent_phase_title(phase)),
      _manager(phase, thread)
    { }
  };
  
  bool G1ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) {
    int phase = lookup_concurrent_phase(phase_name);
    if (phase < 0) return false;
  
    while (!ConcurrentGCPhaseManager::wait_for_phase(phase,
                                                     phase_manager_stack())) {
      assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed");
      if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) {
        // If idle and the goal is !idle, start a collection.
        G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark);
      }
    }
    return true;
  }
  
  void G1ConcurrentMarkThread::run_service() {
    _vtime_start = os::elapsedVTime();
  
    G1CollectedHeap* g1h = G1CollectedHeap::heap();
    G1Policy* policy = g1h->policy();
  
    G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this);
  
    while (!should_terminate()) {
      // wait until started is set.
      sleep_before_next_cycle();
      if (should_terminate()) {
        break;
      }
  
      cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */);
  
      GCIdMark gc_id_mark;
  
      _cm->concurrent_cycle_start();
  
      GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
      {
        ResourceMark rm;
        HandleMark   hm;
        double cycle_start = os::elapsedVTime();
  
        {
          G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this);
          ClassLoaderDataGraph::clear_claimed_marks();
        }
  
        // We have to ensure that we finish scanning the root regions
        // before the next GC takes place. To ensure this we have to
        // make sure that we do not join the STS until the root regions
        // have been scanned. If we did then it's possible that a
        // subsequent GC could block us from joining the STS and proceed
        // without the root regions have been scanned which would be a
        // correctness issue.
  
        {
          G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this);
          _cm->scan_root_regions();
        }
  
        // It would be nice to use the G1ConcPhase class here but
        // the "end" logging is inside the loop and not at the end of
        // a scope. Also, the timer doesn't support nesting.
        // Mimicking the same log output instead.
        {
          G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this);
          jlong mark_start = os::elapsed_counter();
          const char* cm_title = lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK);
          log_info(gc, marking)("%s (%.3fs)",
                                cm_title,
                                TimeHelper::counter_to_seconds(mark_start));
          for (uint iter = 1; !_cm->has_aborted(); ++iter) {
            // Concurrent marking.
            {
              G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this);
              _cm->mark_from_roots();
            }
            if (_cm->has_aborted()) {
              break;
            }
  
            if (G1UseReferencePrecleaning) {
              G1ConcPhase p(G1ConcurrentPhase::PRECLEAN, this);
              _cm->preclean();
            }
  
            // Provide a control point before remark.
            {
              G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this);
            }
            if (_cm->has_aborted()) {
              break;
            }
  
            // Delay remark pause for MMU.
            double mark_end_time = os::elapsedVTime();
            jlong mark_end = os::elapsed_counter();
            _vtime_mark_accum += (mark_end_time - cycle_start);
            delay_to_keep_mmu(policy, true /* remark */);
            if (_cm->has_aborted()) {
              break;
            }
  
            // Pause Remark.
            log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms",
                                  cm_title,
                                  TimeHelper::counter_to_seconds(mark_start),
                                  TimeHelper::counter_to_seconds(mark_end),
                                  TimeHelper::counter_to_millis(mark_end - mark_start));
            mark_manager.set_phase(G1ConcurrentPhase::REMARK, false);
            CMRemark cl(_cm);
            VM_G1Concurrent op(&cl, "Pause Remark");
            VMThread::execute(&op);
            if (_cm->has_aborted()) {
              break;
            } else if (!_cm->restart_for_overflow()) {
              break;              // Exit loop if no restart requested.
            } else {
              // Loop to restart for overflow.
              mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false);
              log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)",
                                    cm_title, iter);
            }
          }
        }
  
        if (!_cm->has_aborted()) {
          G1ConcPhase p(G1ConcurrentPhase::REBUILD_REMEMBERED_SETS, this);
          _cm->rebuild_rem_set_concurrently();
        }
  
        double end_time = os::elapsedVTime();
        // Update the total virtual time before doing this, since it will try
        // to measure it to get the vtime for this marking.
        _vtime_accum = (end_time - _vtime_start);
  
        if (!_cm->has_aborted()) {
          delay_to_keep_mmu(policy, false /* cleanup */);
        }
  
        if (!_cm->has_aborted()) {
          CMCleanup cl_cl(_cm);
          VM_G1Concurrent op(&cl_cl, "Pause Cleanup");
          VMThread::execute(&op);
        }
  
        // We now want to allow clearing of the marking bitmap to be
        // suspended by a collection pause.
        // We may have aborted just before the remark. Do not bother clearing the
        // bitmap then, as it has been done during mark abort.
        if (!_cm->has_aborted()) {
          G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this);
          _cm->cleanup_for_next_mark();
        }
      }
  
      // Update the number of full collections that have been
      // completed. This will also notify the FullGCCount_lock in case a
      // Java thread is waiting for a full GC to happen (e.g., it
      // called System.gc() with +ExplicitGCInvokesConcurrent).
      {
        SuspendibleThreadSetJoiner sts_join;
        g1h->increment_old_marking_cycles_completed(true /* concurrent */);
  
        _cm->concurrent_cycle_end();
      }
  
      cpmanager.set_phase(G1ConcurrentPhase::IDLE, _cm->has_aborted() /* force */);
    }
    _cm->root_regions()->cancel_scan();
  }
  
  void G1ConcurrentMarkThread::stop_service() {
    MutexLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
    CGC_lock->notify_all();
  }
  
  
  void G1ConcurrentMarkThread::sleep_before_next_cycle() {
    // We join here because we don't want to do the "shouldConcurrentMark()"
    // below while the world is otherwise stopped.
    assert(!in_progress(), "should have been cleared");
  
    MonitorLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
    while (!started() && !should_terminate()) {
      ml.wait();
    }
  
    if (started()) {
      set_in_progress();
    }
  }
  