/*

 * Copyright (c) 2001, 2018, 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 "gc/g1/g1CollectedHeap.inline.hpp"

#include "gc/g1/g1ConcurrentMarkThread.inline.hpp"

#include "gc/g1/g1Policy.hpp"

#include "gc/g1/g1VMOperations.hpp"

#include "gc/shared/gcId.hpp"

#include "gc/shared/gcTimer.hpp"

#include "gc/shared/gcTraceTime.inline.hpp"

#include "gc/shared/isGCActiveMark.hpp"

#include "runtime/interfaceSupport.inline.hpp"

void VM_G1CollectFull::doit() {

  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  GCCauseSetter x(g1h, _gc_cause);

  g1h->do_full_collection(false /* clear_all_soft_refs */);

}

VM_G1CollectForAllocation::VM_G1CollectForAllocation(size_t         word_size,

                                                     uint           gc_count_before,

                                                     GCCause::Cause gc_cause,

                                                     bool           should_initiate_conc_mark,

                                                     double         target_pause_time_ms) :

  VM_CollectForAllocation(word_size, gc_count_before, gc_cause),

  _pause_succeeded(false),

  _should_initiate_conc_mark(should_initiate_conc_mark),

  _should_retry_gc(false),

  _target_pause_time_ms(target_pause_time_ms),

  _old_marking_cycles_completed_before(0) {

  guarantee(target_pause_time_ms > 0.0,

            "target_pause_time_ms = %1.6lf should be positive",

            target_pause_time_ms);

  _gc_cause = gc_cause;

}

bool VM_G1CollectForAllocation::doit_prologue() {

  bool res = VM_CollectForAllocation::doit_prologue();

  if (!res) {

    if (_should_initiate_conc_mark) {

      // The prologue can fail for a couple of reasons. The first is that another GC

      // got scheduled and prevented the scheduling of the initial mark GC. The

      // second is that the GC locker may be active and the heap can't be expanded.

      // In both cases we want to retry the GC so that the initial mark pause is

      // actually scheduled. In the second case, however, we should stall until

      // until the GC locker is no longer active and then retry the initial mark GC.

      _should_retry_gc = true;

    }

  }

  return res;

}

void VM_G1CollectForAllocation::doit() {

  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  assert(!_should_initiate_conc_mark || g1h->should_do_concurrent_full_gc(_gc_cause),

      "only a GC locker, a System.gc(), stats update, whitebox, or a hum allocation induced GC should start a cycle");

  if (_word_size > 0) {

    // An allocation has been requested. So, try to do that first.

    _result = g1h->attempt_allocation_at_safepoint(_word_size,

                                                   false /* expect_null_cur_alloc_region */);

    if (_result != NULL) {

      // If we can successfully allocate before we actually do the

      // pause then we will consider this pause successful.

      _pause_succeeded = true;

      return;

    }

  }

  GCCauseSetter x(g1h, _gc_cause);

  if (_should_initiate_conc_mark) {

    // It's safer to read old_marking_cycles_completed() here, given

    // that noone else will be updating it concurrently. Since we'll

    // only need it if we're initiating a marking cycle, no point in

    // setting it earlier.

    _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();

    // At this point we are supposed to start a concurrent cycle. We

    // will do so if one is not already in progress.

    bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);

    // The above routine returns true if we were able to force the

    // next GC pause to be an initial mark; it returns false if a

    // marking cycle is already in progress.

    //

    // If a marking cycle is already in progress just return and skip the

    // pause below - if the reason for requesting this initial mark pause

    // was due to a System.gc() then the requesting thread should block in

    // doit_epilogue() until the marking cycle is complete.

    //

    // If this initial mark pause was requested as part of a humongous

    // allocation then we know that the marking cycle must just have

    // been started by another thread (possibly also allocating a humongous

    // object) as there was no active marking cycle when the requesting

    // thread checked before calling collect() in

    // attempt_allocation_humongous(). Retrying the GC, in this case,

    // will cause the requesting thread to spin inside collect() until the

    // just started marking cycle is complete - which may be a while. So

    // we do NOT retry the GC.

    if (!res) {

      assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");

      if (_gc_cause != GCCause::_g1_humongous_allocation) {

        _should_retry_gc = true;

      }

      return;

    }

  }

  // Try a partial collection of some kind.

  _pause_succeeded = g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);

  if (_pause_succeeded) {

    if (_word_size > 0) {

      // An allocation had been requested. Do it, eventually trying a stronger

      // kind of GC.

      _result = g1h->satisfy_failed_allocation(_word_size, &_pause_succeeded);

    } else {

      if (should_upgrade_to_full) {

        // There has been a request to perform a GC to free some space. We have no

        // information on how much memory has been asked for. In case there are

        // absolutely no regions left to allocate into, do a maximally compacting full GC.

        log_info(gc, ergo)("Attempting maximally compacting collection");

        _pause_succeeded = g1h->do_full_collection(false, /* explicit gc */

                                                   true   /* clear_all_soft_refs */);

      }

    }

    guarantee(_pause_succeeded, "Elevated collections during the safepoint must always succeed.");

  } else {

    assert(_result == NULL, "invariant");

    // The only reason for the pause to not be successful is that, the GC locker is

    // active (or has become active since the prologue was executed). In this case

    // we should retry the pause after waiting for the GC locker to become inactive.

    _should_retry_gc = true;

  }

}

void VM_G1CollectForAllocation::doit_epilogue() {

  VM_CollectForAllocation::doit_epilogue();

  // If the pause was initiated by a System.gc() and

  // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle

  // that just started (or maybe one that was already in progress) to

  // finish.

  if (GCCause::is_user_requested_gc(_gc_cause) &&

      _should_initiate_conc_mark) {

    assert(ExplicitGCInvokesConcurrent,

           "the only way to be here is if ExplicitGCInvokesConcurrent is set");

    G1CollectedHeap* g1h = G1CollectedHeap::heap();

    // In the doit() method we saved g1h->old_marking_cycles_completed()

    // in the _old_marking_cycles_completed_before field. We have to

    // wait until we observe that g1h->old_marking_cycles_completed()

    // has increased by at least one. This can happen if a) we started

    // a cycle and it completes, b) a cycle already in progress

    // completes, or c) a Full GC happens.

    // If the condition has already been reached, there's no point in

    // actually taking the lock and doing the wait.

    if (g1h->old_marking_cycles_completed() <=

                                          _old_marking_cycles_completed_before) {

      // The following is largely copied from CMS

      Thread* thr = Thread::current();

      assert(thr->is_Java_thread(), "invariant");

      JavaThread* jt = (JavaThread*)thr;

      ThreadToNativeFromVM native(jt);

      MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);

      while (g1h->old_marking_cycles_completed() <=

                                          _old_marking_cycles_completed_before) {

        FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);

      }

    }

  }

}

void VM_G1Concurrent::doit() {

  GCIdMark gc_id_mark(_gc_id);

  GCTraceCPUTime tcpu;

  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  GCTraceTime(Info, gc) t(_message, g1h->concurrent_mark()->gc_timer_cm(), GCCause::_no_gc, true);

  TraceCollectorStats tcs(g1h->g1mm()->conc_collection_counters());

  SvcGCMarker sgcm(SvcGCMarker::CONCURRENT);

  IsGCActiveMark x;

  _cl->do_void();

}

bool VM_G1Concurrent::doit_prologue() {

  Heap_lock->lock();

  return true;

}

void VM_G1Concurrent::doit_epilogue() {

  if (Universe::has_reference_pending_list()) {

    Heap_lock->notify_all();

  }

  Heap_lock->unlock();

}