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1 /*
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2 * Copyright 2002-2003 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 //
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26 // PrefetchQueue is a FIFO queue of variable length (currently 8).
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27 //
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28 // We need to examine the performance penalty of variable lengths.
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29 // We may also want to split this into cpu dependant bits.
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30 //
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31
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32 const int PREFETCH_QUEUE_SIZE = 8;
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33
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34 class PrefetchQueue : public CHeapObj {
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35 private:
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36 oop* _prefetch_queue[PREFETCH_QUEUE_SIZE];
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37 unsigned int _prefetch_index;
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38
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39 public:
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40 int length() { return PREFETCH_QUEUE_SIZE; }
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41
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42 inline void clear() {
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43 for(int i=0; i<PREFETCH_QUEUE_SIZE; i++) {
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44 _prefetch_queue[i] = NULL;
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45 }
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46 _prefetch_index = 0;
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47 }
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48
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49 inline oop* push_and_pop(oop* p) {
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50 Prefetch::write((*p)->mark_addr(), 0);
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51 // This prefetch is intended to make sure the size field of array
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52 // oops is in cache. It assumes the the object layout is
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53 // mark -> klass -> size, and that mark and klass are heapword
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54 // sized. If this should change, this prefetch will need updating!
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55 Prefetch::write((*p)->mark_addr() + (HeapWordSize*2), 0);
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56 _prefetch_queue[_prefetch_index++] = p;
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57 _prefetch_index &= (PREFETCH_QUEUE_SIZE-1);
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58 return _prefetch_queue[_prefetch_index];
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59 }
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60
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61 // Stores a NULL pointer in the pop'd location.
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62 inline oop* pop() {
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63 _prefetch_queue[_prefetch_index++] = NULL;
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64 _prefetch_index &= (PREFETCH_QUEUE_SIZE-1);
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65 return _prefetch_queue[_prefetch_index];
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66 }
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67 };
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