JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2001, 2020, 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
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#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 "memory/universe.hpp"
#include "runtime/interfaceSupport.inline.hpp"

void VM_G1CollectFull::doit() {
  G1CollectedHeap* g1h = G1CollectedHeap::heap();
  GCCauseSetter x(g1h, _gc_cause);
  _gc_succeeded = g1h->do_full_collection(true /* explicit_gc */, false /* clear_all_soft_refs */);
}

VM_G1TryInitiateConcMark::VM_G1TryInitiateConcMark(uint gc_count_before,
                                                   GCCause::Cause gc_cause,
                                                   double target_pause_time_ms) :
  VM_GC_Operation(gc_count_before, gc_cause),
  _target_pause_time_ms(target_pause_time_ms),
  _transient_failure(false),
  _cycle_already_in_progress(false),
  _terminating(false),
  _gc_succeeded(false)
{}

bool VM_G1TryInitiateConcMark::doit_prologue() {
  bool result = VM_GC_Operation::doit_prologue();
  // 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.
  if (!result) _transient_failure = true;
  return result;
}

void VM_G1TryInitiateConcMark::doit() {
  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  GCCauseSetter x(g1h, _gc_cause);

  // Record for handling by caller.
  _terminating = g1h->_cm_thread->should_terminate();

  if (_terminating && GCCause::is_user_requested_gc(_gc_cause)) {
    // When terminating, the request to initiate a concurrent cycle will be
    // ignored by do_collection_pause_at_safepoint; instead it will just do
    // a young-only or mixed GC (depending on phase).  For a user request
    // there's no point in even doing that much, so done.  For some non-user
    // requests the alternative GC might still be needed.
  } else if (!g1h->policy()->force_initial_mark_if_outside_cycle(_gc_cause)) {
    // Failure to force the next GC pause to be an initial mark indicates
    // there is already a concurrent marking cycle in progress.  Set flag
    // to notify the caller and return immediately.
    _cycle_already_in_progress = true;
  } else if (!g1h->do_collection_pause_at_safepoint(_target_pause_time_ms)) {
    // Failure to perform the collection at all occurs because GCLocker is
    // active, and we have the bad luck to be the collection request that
    // makes a later _gc_locker collection needed.  (Else we would have hit
    // the GCLocker check in the prologue.)
    _transient_failure = true;
  } else if (g1h->should_upgrade_to_full_gc(_gc_cause)) {
    // GC ran, but we're still in trouble and need a full GC.
    log_info(gc, ergo)("Attempting maximally compacting collection");
    _gc_succeeded = g1h->do_full_collection(false, /* explicit gc */
                                            true /* clear_all_soft_refs */);
    guarantee(_gc_succeeded, "Elevated collections during the safepoint must always succeed");
  } else {
    _gc_succeeded = true;
  }
}

VM_G1CollectForAllocation::VM_G1CollectForAllocation(size_t         word_size,
                                                     uint           gc_count_before,
                                                     GCCause::Cause gc_cause,
                                                     double         target_pause_time_ms) :
  VM_CollectForAllocation(word_size, gc_count_before, gc_cause),
  _gc_succeeded(false),
  _target_pause_time_ms(target_pause_time_ms) {

  guarantee(target_pause_time_ms > 0.0,
            "target_pause_time_ms = %1.6lf should be positive",
            target_pause_time_ms);
  _gc_cause = gc_cause;
}

void VM_G1CollectForAllocation::doit() {
  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  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.
      _gc_succeeded = true;
      return;
    }
  }

  GCCauseSetter x(g1h, _gc_cause);
  // Try a partial collection of some kind.
  _gc_succeeded = g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);

  if (_gc_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, &_gc_succeeded);
    } else if (g1h->should_upgrade_to_full_gc(_gc_cause)) {
      // 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");
      _gc_succeeded = g1h->do_full_collection(false, /* explicit gc */

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