view src/share/vm/gc_implementation/g1/vm_operations_g1.cpp @ 2034:7e37af9d69ef

7011379: G1: overly long concurrent marking cycles Summary: This changeset introduces filtering of SATB buffers at the point when they are about to be enqueued. If this filtering clears enough entries on each buffer, the buffer can then be re-used and not enqueued. This cuts down the number of SATB buffers that need to be processed by the concurrent marking threads. Reviewed-by: johnc, ysr
author tonyp
date Wed, 19 Jan 2011 09:35:17 -0500
parents 631f79e71e90
children 1d1603768966
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 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
 * 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 if you need additional information or have any
 * questions.

#include "precompiled.hpp"
#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
#include "gc_implementation/g1/g1CollectorPolicy.hpp"
#include "gc_implementation/g1/vm_operations_g1.hpp"
#include "gc_implementation/shared/isGCActiveMark.hpp"
#include "gc_implementation/g1/vm_operations_g1.hpp"
#include "runtime/interfaceSupport.hpp"

                                                  unsigned int gc_count_before,
                                                  size_t word_size)
  : VM_G1OperationWithAllocRequest(gc_count_before, word_size) {
  guarantee(word_size > 0, "an allocation should always be requested");

void VM_G1CollectForAllocation::doit() {
  G1CollectedHeap* g1h = G1CollectedHeap::heap();
  _result = g1h->satisfy_failed_allocation(_word_size, &_pause_succeeded);
  assert(_result == NULL || _pause_succeeded,
         "if we get back a result, the pause should have succeeded");

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

                                      unsigned int   gc_count_before,
                                      size_t         word_size,
                                      bool           should_initiate_conc_mark,
                                      double         target_pause_time_ms,
                                      GCCause::Cause gc_cause)
  : VM_G1OperationWithAllocRequest(gc_count_before, word_size),
    _full_collections_completed_before(0) {
  guarantee(target_pause_time_ms > 0.0,
            err_msg("target_pause_time_ms = %1.6lf should be positive",
  guarantee(word_size == 0 || gc_cause == GCCause::_g1_inc_collection_pause,
            "we can only request an allocation if the GC cause is for "
            "an incremental GC pause");
  _gc_cause = gc_cause;

void VM_G1IncCollectionPause::doit() {
  G1CollectedHeap* g1h = G1CollectedHeap::heap();
  assert(!_should_initiate_conc_mark ||
  ((_gc_cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
   (_gc_cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent)),
         "only a GC locker or a System.gc() 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;

  GCCauseSetter x(g1h, _gc_cause);
  if (_should_initiate_conc_mark) {
    // It's safer to read full_collections_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.
    _full_collections_completed_before = g1h->full_collections_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();

  _pause_succeeded =
  if (_pause_succeeded && _word_size > 0) {
    // An allocation had been requested.
    _result = g1h->attempt_allocation_at_safepoint(_word_size,
                                      true /* expect_null_cur_alloc_region */);
  } else {
    assert(_result == NULL, "invariant");

void VM_G1IncCollectionPause::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 (_gc_cause == GCCause::_java_lang_system_gc &&
      _should_initiate_conc_mark) {
           "the only way to be here is if ExplicitGCInvokesConcurrent is set");

    G1CollectedHeap* g1h = G1CollectedHeap::heap();

    // In the doit() method we saved g1h->full_collections_completed()
    // in the _full_collections_completed_before field. We have to
    // wait until we observe that g1h->full_collections_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->full_collections_completed() <=
                                          _full_collections_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->full_collections_completed() <=
                                          _full_collections_completed_before) {

void VM_CGC_Operation::doit() {
  gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
  TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
  TraceTime t(_printGCMessage, PrintGC, true, gclog_or_tty);
  SharedHeap* sh = SharedHeap::heap();
  // This could go away if CollectedHeap gave access to _gc_is_active...
  if (sh != NULL) {
    IsGCActiveMark x;
  } else {

bool VM_CGC_Operation::doit_prologue() {
  SharedHeap::heap()->_thread_holds_heap_lock_for_gc = true;
  return true;

void VM_CGC_Operation::doit_epilogue() {
  SharedHeap::heap()->_thread_holds_heap_lock_for_gc = false;