PseudoLRUPolicy.hh revision 11061 
1/*
2 * Copyright (c) 2007 Mark D. Hill and David A. Wood
3 * Copyright (c) 2013 Advanced Micro Devices, Inc
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are
8 * met: redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer;
10 * redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution;
13 * neither the name of the copyright holders nor the names of its
14 * contributors may be used to endorse or promote products derived from
15 * this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
20 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
21 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
22 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
23 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30#ifndef __MEM_RUBY_STRUCTURES_PSEUDOLRUPOLICY_HH__
31#define __MEM_RUBY_STRUCTURES_PSEUDOLRUPOLICY_HH__
32
33#include "mem/ruby/structures/AbstractReplacementPolicy.hh"
34#include "params/PseudoLRUReplacementPolicy.hh"
35
36/**
37 * Implementation of tree-based pseudo-LRU replacement
38 *
39 * Works for any associativity between 1 and 128.
40 *
41 * Also implements associativities that are not a power of 2 by
42 * ignoring paths that lead to a larger index (i.e. truncating the
43 * tree).  Note that when this occurs, the algorithm becomes less
44 * fair, as it will favor indicies in the larger (by index) half of
45 * the associative set. This is most unfair when the nearest power of
46 * 2 is one below the associativy, and most fair when it is one above.
47 */
48
49class PseudoLRUPolicy : public AbstractReplacementPolicy
50{
51  public:
52    typedef PseudoLRUReplacementPolicyParams Params;
53    PseudoLRUPolicy(const Params * p);
54    ~PseudoLRUPolicy();
55
56    void touch(int64_t set, int64_t way, Tick time);
57    int64_t getVictim(int64_t set) const;
58
59  private:
60    unsigned int m_effective_assoc;    /** nearest (to ceiling) power of 2 */
61    unsigned int m_num_levels;         /** number of levels in the tree */
62    uint64_t* m_trees;                   /** bit representation of the
63                                        * trees, one for each set */
64};
65
66#endif // __MEM_RUBY_STRUCTURES_PSEUDOLRUPOLICY_HH__
67