view src/share/vm/oops/objArrayOop.hpp @ 2861:dc467e8b2c5e

7112743: G1: Reduce overhead of marking closure during evacuation pauses Summary: Parallelize the serial code that was used to mark objects reachable from survivor objects in the collection set. Some minor improvments in the timers used to track the freeing of the collection set along with some tweaks to PrintGCDetails. Reviewed-by: tonyp, brutisso
author johnc
date Thu, 17 Nov 2011 12:40:15 -0800
parents f95d63e2154a
children d8ce2825b193
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 * Copyright (c) 1997, 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 "oops/arrayOop.hpp"

// An objArrayOop is an array containing oops.
// Evaluating "String arg[10]" will create an objArrayOop.

class objArrayOopDesc : public arrayOopDesc {
  friend class objArrayKlass;
  friend class Runtime1;
  friend class psPromotionManager;
  friend class CSetMarkOopClosure;
  friend class G1ParScanPartialArrayClosure;

  template <class T> T* obj_at_addr(int index) const {
    assert(is_within_bounds(index), "index out of bounds");
    return &((T*)base())[index];

  // Give size of objArrayOop in HeapWords minus the header
  static int array_size(int length) {
    const int OopsPerHeapWord = HeapWordSize/heapOopSize;
    assert(OopsPerHeapWord >= 1 && (HeapWordSize % heapOopSize == 0),
           "Else the following (new) computation would be in error");
#ifdef ASSERT
    // The old code is left in for sanity-checking; it'll
    // go away pretty soon. XXX
    // Without UseCompressedOops, this is simply:
    // oop->length() * HeapWordsPerOop;
    // With narrowOops, HeapWordsPerOop is 1/2 or equal 0 as an integer.
    // The oop elements are aligned up to wordSize
    const int HeapWordsPerOop = heapOopSize/HeapWordSize;
    int old_res;
    if (HeapWordsPerOop > 0) {
      old_res = length * HeapWordsPerOop;
    } else {
      old_res = align_size_up(length, OopsPerHeapWord)/OopsPerHeapWord;
#endif  // ASSERT
    int res = ((uint)length + OopsPerHeapWord - 1)/OopsPerHeapWord;
    assert(res == old_res, "Inconsistency between old and new.");
    return res;

  // Returns the offset of the first element.
  static int base_offset_in_bytes() {
    return arrayOopDesc::base_offset_in_bytes(T_OBJECT);

  // base is the address following the header.
  HeapWord* base() const      { return (HeapWord*) arrayOopDesc::base(T_OBJECT); }

  // Accessing
  oop obj_at(int index) const {
    // With UseCompressedOops decode the narrow oop in the objArray to an
    // uncompressed oop.  Otherwise this is simply a "*" operator.
    if (UseCompressedOops) {
      return load_decode_heap_oop(obj_at_addr<narrowOop>(index));
    } else {
      return load_decode_heap_oop(obj_at_addr<oop>(index));

  void obj_at_put(int index, oop value) {
    if (UseCompressedOops) {
      oop_store(obj_at_addr<narrowOop>(index), value);
    } else {
      oop_store(obj_at_addr<oop>(index), value);
  // Sizing
  static int header_size()    { return arrayOopDesc::header_size(T_OBJECT); }
  int object_size()           { return object_size(length()); }

  static int object_size(int length) {
    // This returns the object size in HeapWords.
    uint asz = array_size(length);
    uint osz = align_object_size(header_size() + asz);
    assert(osz >= asz,   "no overflow");
    assert((int)osz > 0, "no overflow");
    return (int)osz;

  // special iterators for index ranges, returns size of object
#define ObjArrayOop_OOP_ITERATE_DECL(OopClosureType, nv_suffix)     \
  int oop_iterate_range(OopClosureType* blk, int start, int end);