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Java example source code file (heapRegionSets.cpp)

This example Java source code file (heapRegionSets.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

freelist_lock-, freeregionlist\:\:check_mt_safety, freeregionlist\:\:verify_region_extra, heapregionlinkedlist\:\:verify_region_extra, heapregionset::verify_region_extra, hrsphasecleanup, humongousregionset\:\:verify_region_extra, masterfreeregionlist\:\:check_mt_safety, masterfreeregionlist\:\:verify_region_extra, masterhumongousregionset\:\:check_mt_safety, oldsets_lock\-, safepointsynchronize::is_at_safepoint

The heapRegionSets.cpp Java example source code

/*
 * Copyright (c) 2011, 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_implementation/g1/heapRegionRemSet.hpp"
#include "gc_implementation/g1/heapRegionSets.hpp"

// Note on the check_mt_safety() methods below:
//
// Verification of the "master" heap region sets / lists that are
// maintained by G1CollectedHeap is always done during a STW pause and
// by the VM thread at the start / end of the pause. The standard
// verification methods all assert check_mt_safety(). This is
// important as it ensures that verification is done without
// concurrent updates taking place at the same time. It follows, that,
// for the "master" heap region sets / lists, the check_mt_safety()
// method should include the VM thread / STW case.

//////////////////// FreeRegionList ////////////////////

const char* FreeRegionList::verify_region_extra(HeapRegion* hr) {
  if (hr->is_young()) {
    return "the region should not be young";
  }
  // The superclass will check that the region is empty and
  // not humongous.
  return HeapRegionLinkedList::verify_region_extra(hr);
}

//////////////////// MasterFreeRegionList ////////////////////

const char* MasterFreeRegionList::verify_region_extra(HeapRegion* hr) {
  // We should reset the RSet for parallel iteration before we add it
  // to the master free list so that it is ready when the region is
  // re-allocated.
  if (!hr->rem_set()->verify_ready_for_par_iteration()) {
    return "the region's RSet should be ready for parallel iteration";
  }
  return FreeRegionList::verify_region_extra(hr);
}

bool MasterFreeRegionList::check_mt_safety() {
  // Master Free List MT safety protocol:
  // (a) If we're at a safepoint, operations on the master free list
  // should be invoked by either the VM thread (which will serialize
  // them) or by the GC workers while holding the
  // FreeList_lock.
  // (b) If we're not at a safepoint, operations on the master free
  // list should be invoked while holding the Heap_lock.

  if (SafepointSynchronize::is_at_safepoint()) {
    guarantee(Thread::current()->is_VM_thread() ||
              FreeList_lock->owned_by_self(),
              hrs_ext_msg(this, "master free list MT safety protocol "
                                "at a safepoint"));
  } else {
    guarantee(Heap_lock->owned_by_self(),
              hrs_ext_msg(this, "master free list MT safety protocol "
                                "outside a safepoint"));
  }

  return FreeRegionList::check_mt_safety();
}

//////////////////// SecondaryFreeRegionList ////////////////////

bool SecondaryFreeRegionList::check_mt_safety() {
  // Secondary Free List MT safety protocol:
  // Operations on the secondary free list should always be invoked
  // while holding the SecondaryFreeList_lock.

  guarantee(SecondaryFreeList_lock->owned_by_self(),
            hrs_ext_msg(this, "secondary free list MT safety protocol"));

  return FreeRegionList::check_mt_safety();
}

//////////////////// OldRegionSet ////////////////////

const char* OldRegionSet::verify_region_extra(HeapRegion* hr) {
  if (hr->is_young()) {
    return "the region should not be young";
  }
  // The superclass will check that the region is not empty and not
  // humongous.
  return HeapRegionSet::verify_region_extra(hr);
}

//////////////////// MasterOldRegionSet ////////////////////

bool MasterOldRegionSet::check_mt_safety() {
  // Master Old Set MT safety protocol:
  // (a) If we're at a safepoint, operations on the master old set
  // should be invoked:
  // - by the VM thread (which will serialize them), or
  // - by the GC workers while holding the FreeList_lock, if we're
  //   at a safepoint for an evacuation pause (this lock is taken
  //   anyway when an GC alloc region is retired so that a new one
  //   is allocated from the free list), or
  // - by the GC workers while holding the OldSets_lock, if we're at a
  //   safepoint for a cleanup pause.
  // (b) If we're not at a safepoint, operations on the master old set
  // should be invoked while holding the Heap_lock.

  if (SafepointSynchronize::is_at_safepoint()) {
    guarantee(Thread::current()->is_VM_thread() ||
              _phase == HRSPhaseEvacuation && FreeList_lock->owned_by_self() ||
              _phase == HRSPhaseCleanup && OldSets_lock->owned_by_self(),
              hrs_ext_msg(this, "master old set MT safety protocol "
                                "at a safepoint"));
  } else {
    guarantee(Heap_lock->owned_by_self(),
              hrs_ext_msg(this, "master old set MT safety protocol "
                                "outside a safepoint"));
  }

  return OldRegionSet::check_mt_safety();
}

//////////////////// HumongousRegionSet ////////////////////

const char* HumongousRegionSet::verify_region_extra(HeapRegion* hr) {
  if (hr->is_young()) {
    return "the region should not be young";
  }
  // The superclass will check that the region is not empty and
  // humongous.
  return HeapRegionSet::verify_region_extra(hr);
}

//////////////////// MasterHumongousRegionSet ////////////////////

bool MasterHumongousRegionSet::check_mt_safety() {
  // Master Humongous Set MT safety protocol:
  // (a) If we're at a safepoint, operations on the master humongous
  // set should be invoked by either the VM thread (which will
  // serialize them) or by the GC workers while holding the
  // OldSets_lock.
  // (b) If we're not at a safepoint, operations on the master
  // humongous set should be invoked while holding the Heap_lock.

  if (SafepointSynchronize::is_at_safepoint()) {
    guarantee(Thread::current()->is_VM_thread() ||
              OldSets_lock->owned_by_self(),
              hrs_ext_msg(this, "master humongous set MT safety protocol "
                                "at a safepoint"));
  } else {
    guarantee(Heap_lock->owned_by_self(),
              hrs_ext_msg(this, "master humongous set MT safety protocol "
                                "outside a safepoint"));
  }

  return HumongousRegionSet::check_mt_safety();
}

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