112 lines
3.7 KiB
C++
112 lines
3.7 KiB
C++
/*
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* Copyright (c) 2013 Advanced Micro Devices, Inc
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Author: Derek Hower
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*/
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#include "mem/ruby/structures/PseudoLRUPolicy.hh"
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PseudoLRUPolicy::PseudoLRUPolicy(const Params * p)
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: AbstractReplacementPolicy(p)
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{
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// associativity cannot exceed capacity of tree representation
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assert(m_num_sets > 0 &&
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m_assoc > 1 &&
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m_assoc <= (int64_t) sizeof(uint64_t)*4);
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m_trees = NULL;
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m_num_levels = 0;
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m_effective_assoc = 1;
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while (m_effective_assoc < m_assoc) {
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// effective associativity is ceiling power of 2
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m_effective_assoc <<= 1;
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}
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int tmp_assoc = m_effective_assoc;
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while (true) {
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tmp_assoc /= 2;
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if (!tmp_assoc) break;
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m_num_levels++;
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}
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assert(m_num_levels < sizeof(unsigned int)*4);
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m_trees = new uint64_t[m_num_sets];
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for (unsigned i = 0; i < m_num_sets; i++) {
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m_trees[i] = 0;
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}
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}
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PseudoLRUPolicy *
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PseudoLRUReplacementPolicyParams::create()
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{
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return new PseudoLRUPolicy(this);
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}
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PseudoLRUPolicy::~PseudoLRUPolicy()
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{
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if (m_trees != NULL)
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delete[] m_trees;
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}
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void
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PseudoLRUPolicy::touch(int64_t set, int64_t index, Tick time)
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{
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assert(index >= 0 && index < m_assoc);
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assert(set >= 0 && set < m_num_sets);
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int tree_index = 0;
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int node_val;
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for (int i = m_num_levels - 1; i >= 0; i--) {
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node_val = (index >> i)&1;
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if (node_val)
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m_trees[set] |= node_val << tree_index;
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else
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m_trees[set] &= ~(1 << tree_index);
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tree_index = node_val ? (tree_index*2)+2 : (tree_index*2)+1;
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}
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m_last_ref_ptr[set][index] = time;
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}
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int64_t
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PseudoLRUPolicy::getVictim(int64_t set) const
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{
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int64_t index = 0;
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int tree_index = 0;
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int node_val;
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for (unsigned i = 0; i < m_num_levels; i++){
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node_val = (m_trees[set] >> tree_index) & 1;
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index += node_val ? 0 : (m_effective_assoc >> (i + 1));
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tree_index = node_val ? (tree_index * 2) + 1 : (tree_index * 2) + 2;
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}
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assert(index >= 0 && index < m_effective_assoc);
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/* return either the found index or the max possible index */
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/* NOTE: this is not a fair replacement when assoc is not a power of 2 */
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return (index > (m_assoc - 1)) ? m_assoc - 1 : index;
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}
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