src/mem/ruby/structures/PseudoLRUPolicy.hh

   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
  49 class PseudoLRUPolicy : public AbstractReplacementPolicy
  50 {
  51   public:
  52     typedef PseudoLRUReplacementPolicyParams Params;
  53     PseudoLRUPolicy(const Params * p);
  54     ~PseudoLRUPolicy();
  55
  56     void touch(int64 set, int64 way, Tick time);
  57     int64 getVictim(int64 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* m_trees;                   /** bit representation of the
  63                                         * trees, one for each set */
  64 };
  65
  66 #endif // __MEM_RUBY_STRUCTURES_PSEUDOLRUPOLICY_HH__