view src/share/vm/gc_implementation/parallelScavenge/prefetchQueue.hpp @ 0:a61af66fc99e

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author duke
date Sat, 01 Dec 2007 00:00:00 +0000
children ba764ed4b6f2
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 * Copyright 2002-2003 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit if you need additional information or
 * have any questions.

// PrefetchQueue is a FIFO queue of variable length (currently 8).
// We need to examine the performance penalty of variable lengths.
// We may also want to split this into cpu dependant bits.

const int PREFETCH_QUEUE_SIZE  = 8;

class PrefetchQueue : public CHeapObj {
  oop*                         _prefetch_queue[PREFETCH_QUEUE_SIZE];
  unsigned int                 _prefetch_index;

  int length() { return PREFETCH_QUEUE_SIZE; }

  inline void clear() {
    for(int i=0; i<PREFETCH_QUEUE_SIZE; i++) {
      _prefetch_queue[i] = NULL;
    _prefetch_index = 0;

  inline oop* push_and_pop(oop* p) {
    Prefetch::write((*p)->mark_addr(), 0);
    // This prefetch is intended to make sure the size field of array
    // oops is in cache. It assumes the the object layout is
    // mark -> klass -> size, and that mark and klass are heapword
    // sized. If this should change, this prefetch will need updating!
    Prefetch::write((*p)->mark_addr() + (HeapWordSize*2), 0);
    _prefetch_queue[_prefetch_index++] = p;
    _prefetch_index &= (PREFETCH_QUEUE_SIZE-1);
    return _prefetch_queue[_prefetch_index];

  // Stores a NULL pointer in the pop'd location.
  inline oop* pop() {
    _prefetch_queue[_prefetch_index++] = NULL;
    _prefetch_index &= (PREFETCH_QUEUE_SIZE-1);
    return _prefetch_queue[_prefetch_index];