class NRURP(BRRIPRP):
btp = 0
max_RRPV = 1
+
+class TreePLRURP(BaseReplacementPolicy):
+ type = 'TreePLRURP'
+ cxx_class = 'TreePLRURP'
+ cxx_header = "mem/cache/replacement_policies/tree_plru_rp.hh"
+ num_leaves = Param.Int(Parent.assoc, "Number of leaves in each tree")
Source('mru_rp.cc')
Source('random_rp.cc')
Source('second_chance_rp.cc')
+Source('tree_plru_rp.cc')
/**
* @file
* Declaration of a Least Recently Used replacement policy.
- * The victim is chosen using the timestamp. The timestamp may be true or
- * pseudo, depending on the quantity of bits allocated for that.
+ * The victim is chosen using the last touch timestamp.
*/
#ifndef __MEM_CACHE_REPLACEMENT_POLICIES_LRU_RP_HH__
--- /dev/null
+/**
+ * Copyright (c) 2018 Inria
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Daniel Carvalho
+ */
+
+/**
+ * @file
+ * Definitions of a Tree-PLRU replacement policy, along with some helper
+ * tree indexing functions, which map an index to the tree 2D-array.
+ */
+
+#include "mem/cache/replacement_policies/tree_plru_rp.hh"
+
+#include <memory>
+
+#include "base/intmath.hh"
+#include "params/TreePLRURP.hh"
+
+/**
+ * Get the index of the parent of the given indexed subtree.
+ *
+ * @param Index of the queried tree.
+ * @return The index of the parent tree.
+ */
+static uint64_t
+parentIndex(const uint64_t index)
+{
+ return std::floor((index-1)/2);
+}
+
+/**
+ * Get index of the subtree on the left of the given indexed tree.
+ *
+ * @param index The index of the queried tree.
+ * @return The index of the subtree to the left of the queried tree.
+ */
+static uint64_t
+leftSubtreeIndex(const uint64_t index)
+{
+ return 2*index + 1;
+}
+
+/**
+ * Get index of the subtree on the right of the given indexed tree.
+ *
+ * @param index The index of the queried tree.
+ * @return The index of the subtree to the right of the queried tree.
+ */
+static uint64_t
+rightSubtreeIndex(const uint64_t index)
+{
+ return 2*index + 2;
+}
+
+/**
+ * Find out if the subtree at index corresponds to the right or left subtree
+ * of its parent tree.
+ *
+ * @param index The index of the subtree.
+ * @return True if it is a right subtree, false otherwise.
+ */
+static bool
+isRightSubtree(const uint64_t index)
+{
+ return index%2 == 0;
+}
+
+TreePLRURP::TreePLRUReplData::TreePLRUReplData(
+ const uint64_t index, std::shared_ptr<PLRUTree> tree)
+ : index(index), tree(tree)
+{
+}
+
+TreePLRURP::TreePLRURP(const Params *p)
+ : BaseReplacementPolicy(p), numLeaves(p->num_leaves), count(0),
+ treeInstance(nullptr)
+{
+ fatal_if(!isPowerOf2(numLeaves),
+ "Number of leaves must be non-zero and a power of 2");
+}
+
+void
+TreePLRURP::invalidate(
+ const std::shared_ptr<ReplacementData>& replacement_data) const
+{
+ // Cast replacement data
+ std::shared_ptr<TreePLRUReplData> treePLRU_replacement_data =
+ std::static_pointer_cast<TreePLRUReplData>(replacement_data);
+ PLRUTree* tree = treePLRU_replacement_data->tree.get();
+
+ // Index of the tree entry we are currently checking
+ // Make this entry the new LRU entry
+ uint64_t tree_index = treePLRU_replacement_data->index;
+
+ // Parse and update tree to make it point to the new LRU
+ do {
+ // Store whether we are coming from a left or right node
+ const bool right = isRightSubtree(tree_index);
+
+ // Go to the parent tree node
+ tree_index = parentIndex(tree_index);
+
+ // Update parent node to make it point to the node we just came from
+ tree->at(tree_index) = right;
+ } while (tree_index != 0);
+}
+
+void
+TreePLRURP::touch(const std::shared_ptr<ReplacementData>& replacement_data)
+const
+{
+ // Cast replacement data
+ std::shared_ptr<TreePLRUReplData> treePLRU_replacement_data =
+ std::static_pointer_cast<TreePLRUReplData>(replacement_data);
+ PLRUTree* tree = treePLRU_replacement_data->tree.get();
+
+ // Index of the tree entry we are currently checking
+ // Make this entry the MRU entry
+ uint64_t tree_index = treePLRU_replacement_data->index;
+
+ // Parse and update tree to make every bit point away from the new MRU
+ do {
+ // Store whether we are coming from a left or right node
+ const bool right = isRightSubtree(tree_index);
+
+ // Go to the parent tree node
+ tree_index = parentIndex(tree_index);
+
+ // Update node to not point to the touched leaf
+ tree->at(tree_index) = !right;
+ } while (tree_index != 0);
+}
+
+void
+TreePLRURP::reset(const std::shared_ptr<ReplacementData>& replacement_data)
+const
+{
+ // A reset has the same functionality of a touch
+ touch(replacement_data);
+}
+
+ReplaceableEntry*
+TreePLRURP::getVictim(const ReplacementCandidates& candidates) const
+{
+ // There must be at least one replacement candidate
+ assert(candidates.size() > 0);
+
+ // Get tree
+ const PLRUTree* tree = std::static_pointer_cast<TreePLRUReplData>(
+ candidates[0]->replacementData)->tree.get();
+
+ // Index of the tree entry we are currently checking. Start with root.
+ uint64_t tree_index = 0;
+
+ // Parse tree
+ while (tree_index < tree->size()) {
+ // Go to the next tree entry
+ if (tree->at(tree_index)) {
+ tree_index = rightSubtreeIndex(tree_index);
+ } else {
+ tree_index = leftSubtreeIndex(tree_index);
+ }
+ }
+
+ // The tree index is currently at the leaf of the victim displaced by the
+ // number of non-leaf nodes
+ return candidates[tree_index - (numLeaves - 1)];
+}
+
+std::shared_ptr<ReplacementData>
+TreePLRURP::instantiateEntry()
+{
+ // Generate a tree instance every numLeaves created
+ if (count % numLeaves == 0) {
+ treeInstance = new PLRUTree(numLeaves - 1, false);
+ }
+
+ // Create replacement data using current tree instance
+ TreePLRUReplData* treePLRUReplData = new TreePLRUReplData(
+ (count % numLeaves) + numLeaves - 1,
+ std::shared_ptr<PLRUTree>(treeInstance));
+
+ // Update instance counter
+ count++;
+
+ return std::shared_ptr<ReplacementData>(treePLRUReplData);
+}
+
+TreePLRURP*
+TreePLRURPParams::create()
+{
+ return new TreePLRURP(this);
+}
--- /dev/null
+/**
+ * Copyright (c) 2018 Inria
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Daniel Carvalho
+ */
+
+/**
+ * @file
+ * Declaration of a Pseudo-Least Recently Used replacement policy.
+ * The victim is chosen using a tree of bit timestamps.
+ *
+ * A tree contains consists of leafs that represent the direction to take when
+ * searching for the LRU entry.
+ *
+ * Let's assume each tree contains 8 replacement data entries. For example, if
+ * these entries are named from A to H, and the tree's bits are:
+ * ____1____
+ * __0__ __1__
+ * _0_ _1_ _1_ _0_
+ * A B C D E F G H
+ *
+ * Then the current PLRU entry is given by the sequence:
+ * 1 (get right child) -> 1 (get right child) -> 0 (get left child) -> G
+ *
+ * When an entry is touched the bits of the parent nodes are iteratively
+ * updated to point away from it. Therefore, if entry B is touched, its parent,
+ * grandparents, etc would be updated, and we'd end up with the following tree:
+ * ____1____
+ * __1__ __1__
+ * _0_ _1_ _1_ _0_
+ * A B C D E F G H
+ *
+ * Explanation: The parent of B must point away from it, that is, to the left
+ * child, but it is already doing so, so it is left unmodified (0). Then the
+ * grandparent must point to the right subtree, as B belongs to its left
+ * subtree (0 becomes 1). Lastly, the root must point away from the
+ * grandparent, so it is left unmodified (0).
+ *
+ * For invalidations the process is similar to touches, but instead of pointing
+ * away, the bits point toward the entry.
+ *
+ * Consecutive calls to instantiateEntry() use the same tree up to numLeaves.
+ * When numLeaves replacement datas have been created, a new tree is generated,
+ * and the counter is reset.
+ */
+
+#ifndef __MEM_CACHE_REPLACEMENT_POLICIES_TREE_PLRU_RP_HH__
+#define __MEM_CACHE_REPLACEMENT_POLICIES_TREE_PLRU_RP_HH__
+
+#include "mem/cache/replacement_policies/base.hh"
+
+struct TreePLRURPParams;
+
+class TreePLRURP : public BaseReplacementPolicy
+{
+ private:
+ /**
+ * Instead of implementing the tree itself with pointers, it is implemented
+ * as an array of bits. The index of the node defines its position in the
+ * tree, and its parent. Index 0 represents the root, 1 is its left node,
+ * and 2 is its right node. Then, in a BFS fashion this is expanded to the
+ * following nodes (3 and 4 are respectively 1's left and right nodes, and
+ * 5 and 6 are 2's left and right nodes, and so on).
+ *
+ * i.e., the following trees are equivalent in this representation:
+ * ____1____
+ * __0__ __1__
+ * _0_ _1_ _1_ _0_
+ * A B C D E F G H
+ *
+ * 1 0 1 0 1 1 0
+ *
+ * Notice that the replacement data entries are not represented in the tree
+ * to avoid unnecessary storage costs.
+ */
+ typedef std::vector<bool> PLRUTree;
+
+ /**
+ * Number of leaves that share a single replacement data.
+ */
+ const uint64_t numLeaves;
+
+ /**
+ * Count of the number of sharers of a replacement data. It is used when
+ * instantiating entries to share a replacement data among many replaceable
+ * entries.
+ */
+ uint64_t count;
+
+ /**
+ * Holds the latest temporary tree instance created by instantiateEntry().
+ */
+ PLRUTree* treeInstance;
+
+ protected:
+ /**
+ * Tree-PLRU-specific implementation of replacement data. Each replacement
+ * data shares its tree with other entries.
+ */
+ struct TreePLRUReplData : ReplacementData
+ {
+ /**
+ * Theoretical index of this replacement data in the tree. In practice,
+ * the corresponding node does not exist, as the tree stores only the
+ * nodes that are not leaves.
+ */
+ const uint64_t index;
+
+ /**
+ * Shared tree pointer. A tree is shared between numLeaves nodes, so
+ * that accesses to a replacement data entry updates the PLRU bits of
+ * all other replacement data entries in its set.
+ */
+ std::shared_ptr<PLRUTree> tree;
+
+ /**
+ * Default constructor. Invalidate data.
+ *
+ * @param index Index of the corresponding entry in the tree.
+ * @param tree The shared tree pointer.
+ */
+ TreePLRUReplData(const uint64_t index, std::shared_ptr<PLRUTree> tree);
+ };
+
+ public:
+ /** Convenience typedef. */
+ typedef TreePLRURPParams Params;
+
+ /**
+ * Construct and initiliaze this replacement policy.
+ */
+ TreePLRURP(const Params *p);
+
+ /**
+ * Destructor.
+ */
+ ~TreePLRURP() {}
+
+ /**
+ * Invalidate replacement data to set it as the next probable victim.
+ * Makes tree leaf of replacement data the LRU (tree bits point to it).
+ *
+ * @param replacement_data Replacement data to be invalidated.
+ */
+ void invalidate(const std::shared_ptr<ReplacementData>& replacement_data)
+ const override;
+
+ /**
+ * Touch an entry to update its replacement data.
+ * Makes tree leaf of replacement data the MRU.
+ *
+ * @param replacement_data Replacement data to be touched.
+ */
+ void touch(const std::shared_ptr<ReplacementData>& replacement_data) const
+ override;
+
+ /**
+ * Reset replacement data. Used when an entry is inserted. Provides the
+ * same functionality as touch().
+ *
+ * @param replacement_data Replacement data to be reset.
+ */
+ void reset(const std::shared_ptr<ReplacementData>& replacement_data) const
+ override;
+
+ /**
+ * Find replacement victim using TreePLRU bits. It is assumed that all
+ * candidates share the same replacement data tree.
+ *
+ * @param candidates Replacement candidates, selected by indexing policy.
+ * @return Replacement entry to be replaced.
+ */
+ ReplaceableEntry* getVictim(const ReplacementCandidates& candidates) const
+ override;
+
+ /**
+ * Instantiate a replacement data entry. Consecutive calls to this
+ * function use the same tree up to numLeaves. When numLeaves replacement
+ * data have been created, a new tree is generated, and the counter is
+ * reset.
+ * Therefore, it is essential that entries that share the same replacement
+ * data call this function consecutively.
+ *
+ * @return A shared pointer to the new replacement data.
+ */
+ std::shared_ptr<ReplacementData> instantiateEntry() override;
+};
+
+#endif // __MEM_CACHE_REPLACEMENT_POLICIES_TREE_PLRU_RP_HH__
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