1 #ifdef USE_PRAGMA_IDENT_HDR
   2 #pragma ident "@(#)prefetchQueue.hpp    1.13 07/05/05 17:05:28 JVM"
   3 #endif
   4 /*
   5  * Copyright 2002-2008 Sun Microsystems, Inc.  All Rights Reserved.
   6  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   7  *
   8  * This code is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License version 2 only, as
  10  * published by the Free Software Foundation.
  11  *
  12  * This code is distributed in the hope that it will be useful, but WITHOUT
  13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15  * version 2 for more details (a copy is included in the LICENSE file that
  16  * accompanied this code).
  17  *
  18  * You should have received a copy of the GNU General Public License version
  19  * 2 along with this work; if not, write to the Free Software Foundation,
  20  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  21  *
  22  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  23  * CA 95054 USA or visit www.sun.com if you need additional information or
  24  * have any questions.
  25  *  
  26  */
  27 
  28 //
  29 // PrefetchQueue is a FIFO queue of variable length (currently 8).
  30 //
  31 // We need to examine the performance penalty of variable lengths.
  32 // We may also want to split this into cpu dependant bits.
  33 //
  34 
  35 const int PREFETCH_QUEUE_SIZE  = 8;
  36 
  37 class PrefetchQueue : public CHeapObj {
  38  private:
  39   void* _prefetch_queue[PREFETCH_QUEUE_SIZE];
  40   uint  _prefetch_index;
  41 
  42  public:
  43   int length() { return PREFETCH_QUEUE_SIZE; }
  44 
  45   inline void clear() {
  46     for(int i=0; i<PREFETCH_QUEUE_SIZE; i++) {
  47       _prefetch_queue[i] = NULL;
  48     }
  49     _prefetch_index = 0;
  50   }
  51 
  52   template <class T> inline void* push_and_pop(T* p) {
  53     oop o = oopDesc::load_decode_heap_oop_not_null(p);
  54     Prefetch::write(o->mark_addr(), 0);
  55     // This prefetch is intended to make sure the size field of array
  56     // oops is in cache. It assumes the the object layout is
  57     // mark -> klass -> size, and that mark and klass are heapword
  58     // sized. If this should change, this prefetch will need updating!
  59     Prefetch::write(o->mark_addr() + (HeapWordSize*2), 0);
  60     _prefetch_queue[_prefetch_index++] = p;
  61     _prefetch_index &= (PREFETCH_QUEUE_SIZE-1);
  62     return _prefetch_queue[_prefetch_index];
  63   }
  64 
  65   // Stores a NULL pointer in the pop'd location.
  66   inline void* pop() {
  67     _prefetch_queue[_prefetch_index++] = NULL;
  68     _prefetch_index &= (PREFETCH_QUEUE_SIZE-1);
  69     return _prefetch_queue[_prefetch_index];
  70   }
  71 };
  72 
  73 
  74