PseudoLRUPolicy.cc revision 10970
1/* 2 * Copyright (c) 2013 Advanced Micro Devices, Inc 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are 7 * met: redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer; 9 * redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution; 12 * neither the name of the copyright holders nor the names of its 13 * contributors may be used to endorse or promote products derived from 14 * this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 * 28 * Author: Derek Hower 29 */ 30 31#include "mem/ruby/structures/PseudoLRUPolicy.hh" 32 33 34 35PseudoLRUPolicy::PseudoLRUPolicy(const Params * p) 36 : AbstractReplacementPolicy(p) 37{ 38 // associativity cannot exceed capacity of tree representation 39 assert(m_num_sets > 0 && 40 m_assoc > 1 && 41 m_assoc <= (int64) sizeof(uint64)*4); 42 43 m_trees = NULL; 44 m_num_levels = 0; 45 46 m_effective_assoc = 1; 47 while (m_effective_assoc < m_assoc) { 48 // effective associativity is ceiling power of 2 49 m_effective_assoc <<= 1; 50 } 51 int tmp_assoc = m_effective_assoc; 52 while (true) { 53 tmp_assoc /= 2; 54 if(!tmp_assoc) break; 55 m_num_levels++; 56 } 57 assert(m_num_levels < sizeof(unsigned int)*4); 58 m_trees = new uint64[m_num_sets]; 59 for (unsigned i = 0; i < m_num_sets; i++) { 60 m_trees[i] = 0; 61 } 62} 63 64PseudoLRUPolicy * 65PseudoLRUReplacementPolicyParams::create() 66{ 67 return new PseudoLRUPolicy(this); 68} 69 70 71PseudoLRUPolicy::~PseudoLRUPolicy() 72{ 73 if (m_trees != NULL) 74 delete[] m_trees; 75} 76 77void 78PseudoLRUPolicy::touch(int64 set, int64 index, Tick time) 79{ 80 assert(index >= 0 && index < m_assoc); 81 assert(set >= 0 && set < m_num_sets); 82 83 int tree_index = 0; 84 int node_val; 85 for (int i = m_num_levels - 1; i >= 0; i--) { 86 node_val = (index >> i)&1; 87 if (node_val) 88 m_trees[set] |= node_val << tree_index; 89 else 90 m_trees[set] &= ~(1 << tree_index); 91 tree_index = node_val ? (tree_index*2)+2 : (tree_index*2)+1; 92 } 93 m_last_ref_ptr[set][index] = time; 94} 95 96int64 97PseudoLRUPolicy::getVictim(int64 set) const 98{ 99 int64 index = 0; 100 101 int tree_index = 0; 102 int node_val; 103 for (unsigned i = 0; i < m_num_levels; i++){ 104 node_val = (m_trees[set] >> tree_index) & 1; 105 index += node_val ? 0 : (m_effective_assoc >> (i + 1)); 106 tree_index = node_val ? (tree_index * 2) + 1 : (tree_index * 2) + 2; 107 } 108 assert(index >= 0 && index < m_effective_assoc); 109 110 /* return either the found index or the max possible index */ 111 /* NOTE: this is not a fair replacement when assoc is not a power of 2 */ 112 return (index > (m_assoc - 1)) ? m_assoc - 1 : index; 113} 114