hotspot/src/share/vm/gc/g1/youngList.hpp

/*
 * Copyright (c) 2015, 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.
 *
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#ifndef SHARE_VM_GC_G1_YOUNGLIST_HPP
#define SHARE_VM_GC_G1_YOUNGLIST_HPP

#include "memory/allocation.hpp"
#include "runtime/globals.hpp"

class YoungList : public CHeapObj<mtGC> {
private:
  G1CollectedHeap* _g1h;

  HeapRegion* _head;

  HeapRegion* _survivor_head;
  HeapRegion* _survivor_tail;

  HeapRegion* _curr;

  uint        _length;
  uint        _survivor_length;

  size_t      _last_sampled_rs_lengths;
  size_t      _sampled_rs_lengths;

  void         empty_list(HeapRegion* list);

public:
  YoungList(G1CollectedHeap* g1h);

  void         push_region(HeapRegion* hr);
  void         add_survivor_region(HeapRegion* hr);

  void         empty_list();
  bool         is_empty() { return _length == 0; }
  uint         length() { return _length; }
  uint         eden_length() { return length() - survivor_length(); }
  uint         survivor_length() { return _survivor_length; }

  // Currently we do not keep track of the used byte sum for the
  // young list and the survivors and it'd be quite a lot of work to
  // do so. When we'll eventually replace the young list with
  // instances of HeapRegionLinkedList we'll get that for free. So,
  // we'll report the more accurate information then.
  size_t       eden_used_bytes() {
    assert(length() >= survivor_length(), "invariant");
    return (size_t) eden_length() * HeapRegion::GrainBytes;
  }
  size_t       survivor_used_bytes() {
    return (size_t) survivor_length() * HeapRegion::GrainBytes;
  }

  void rs_length_sampling_init();
  bool rs_length_sampling_more();
  void rs_length_sampling_next();

  void reset_sampled_info() {
    _last_sampled_rs_lengths =   0;
  }
  size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }

  // for development purposes
  void reset_auxilary_lists();
  void clear() { _head = NULL; _length = 0; }

  void clear_survivors() {
    _survivor_head    = NULL;
    _survivor_tail    = NULL;
    _survivor_length  = 0;
  }

  HeapRegion* first_region() { return _head; }
  HeapRegion* first_survivor_region() { return _survivor_head; }
  HeapRegion* last_survivor_region() { return _survivor_tail; }

  // debugging
  bool          check_list_well_formed();
  bool          check_list_empty(bool check_sample = true);
  void          print();
};

#endif // SHARE_VM_GC_G1_YOUNGLIST_HPP