| /* |
| * Copyright (c) 2014-2015 ARM Limited |
| * All rights reserved |
| * |
| * The license below extends only to copyright in the software and shall |
| * not be construed as granting a license to any other intellectual |
| * property including but not limited to intellectual property relating |
| * to a hardware implementation of the functionality of the software |
| * licensed hereunder. You may use the software subject to the license |
| * terms below provided that you ensure that this notice is replicated |
| * unmodified and in its entirety in all distributions of the software, |
| * modified or unmodified, in source code or in binary form. |
| * |
| * 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 |
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| */ |
| |
| #ifndef __MEM_STACK_DIST_CALC_HH__ |
| #define __MEM_STACK_DIST_CALC_HH__ |
| |
| #include <limits> |
| #include <map> |
| #include <vector> |
| |
| #include "base/types.hh" |
| |
| namespace gem5 |
| { |
| |
| /** |
| * The stack distance calculator is a passive object that merely |
| * observes the addresses pass to it. It calculates stack distances |
| * of incoming addresses based on the partial sum hierarchy tree |
| * algorithm described by Alamasi et al. |
| * http://doi.acm.org/10.1145/773039.773043. |
| * |
| * A tree structure is maintained and updated at each transaction |
| * (unique or non-unique). The tree is implemented as an STL vector |
| * with layers of the form <map> Each layer in this tree is an |
| * ordered map <uint64_t, Node*>. Nodes are structs which take form |
| * of leaf, intermediate and root nodes. For example, in a tree with 3 |
| * layers, tree[0][5] gives a leaf node pointer for key=5 tree[1][1] |
| * gives an intermediate node pointer for key=1 tree[2][0] gives the |
| * root node in the tree. |
| * |
| * At every transaction a hash-map (aiMap) is looked up to check if |
| * the address was already encountered before. Based on this lookup a |
| * transaction can be termed as unique or non-unique. |
| * |
| * In addition to the normal stack distance calculation, a feature to |
| * mark an old node in the tree is added. This is useful if it is |
| * required to see the reuse pattern. For example, BackInvalidates |
| * from a lower level (e.g. membus to L2), can be marked (isMarked |
| * flag of Node set to True). Then later if this same address is |
| * accessed (by L1), the value of the isMarked flag would be |
| * True. This would give some insight on how the BackInvalidates |
| * policy of the lower level affect the read/write accesses in an |
| * application. |
| * |
| * There are two functions provided to interface with the calculator: |
| * 1. pair<uint64_t, bool> calcStackDistAndUpdate(Addr r_address, |
| * bool addNewNode) |
| * At every unique transaction a new leaf node is added at tree[0](leaf layer) |
| * and linked to the layer above (if addNewNode is True). The sums of all |
| * the intermediate nodes is updated till the root. The stack-distance is |
| * returned as a Constant representing INFINITY. |
| * |
| * At every non-unique transaction the tree is traversed from the |
| * leaf at the returned index to the root, the old node is deleted |
| * from the tree, and the sums (to the right are collected) and |
| * decremented. The collected sum represets the stack distance of the |
| * found node. If this node was marked then a bool flag set to True |
| * is returned with the stack_distance. During this operation a node |
| * is discarded at the leaf layer always. Moreover during the |
| * traversal upwards using the updateSum() method, if an intermediate |
| * node is found with no children connected to it, then that is |
| * discarded too. |
| * |
| * The return value of this function is a pair representing the |
| * stack_distance and the value of the marked flag. |
| * |
| * 2. pair<uint64_t , bool> calcStackDist(Addr r_address, bool mark) |
| * This is a stripped down version of the above function which is used to |
| * just inspect the tree, and mark a leaf node (if mark flag is set). The |
| * functionality to add a new node is removed. |
| * |
| * At every unique transaction the stack-distance is returned as a constant |
| * representing INFINITY. |
| * |
| * At every non-unique transaction the tree is traversed from the |
| * leaf at the returned index to the root, and the sums (to the right) |
| * are collected. The collected sum represets the stack distance of |
| * the found node. |
| * |
| * This function does NOT Modify the stack. (No node is added or |
| * deleted). It is just used to mark a node already created and get |
| * its stack distance. |
| * |
| * The return value of this function is a pair representing the stack |
| * distance and the value of the marked flag. |
| * |
| * The table below depicts the usage of the Algorithm using the functions: |
| * pair<uint64_t Stack_dist, bool isMarked> calcStackDistAndUpdate |
| * (Addr r_address, bool addNewNode) |
| * pair<uint64_t Stack_dist, bool isMarked> calcStackDist |
| * (Addr r_address, bool mark) |
| * |
| * | Function | Arguments |Return Val |Use For| |
| * |calcStackDistAndUpdate|r_address, True|I/SD,False |A,GD,GM| |
| * |calcStackDistAndUpdate|r_address,False|SD,prevMark|D,GD,GM| |
| * |calcStackDist |r_address,False|SD,prevMark| GD,GM| |
| * |calcStackDist |r_address, True|SD,prevMark| GD,GM| |
| * |
| * (*A: Allocate an address in stack, if old entry present then it is deleted, |
| * *U: Delete old-address from stack, no new entry is added |
| * *GD: Get-Stack distance of an address, |
| * *GM: Get value of Mark flag, indicates if that address has been touched |
| * before, |
| * *I: stack-distance = infinity, |
| * *SD: Stack Distance |
| * *r_address: address to be added, *prevMark: value of isMarked flag |
| * of the Node) |
| * |
| * Invalidates refer to a type of packet that removes something from |
| * a cache, either autonoumously (due-to cache's own replacement |
| * policy), or snoops from other caches which invalidate something |
| * inside our cache. |
| * |
| * Usage | Function to use |Typical Use | |
| * Add new entry |calcStackDistAndUpdate|Read/Write Allocate | |
| * Delete Old Entry |calcStackDistAndUpdate|Writebacks/Cleanevicts| |
| * Dist.of Old entry|calcStackDist |Cleanevicts/Invalidate| |
| * |
| * Node Balancing: The tree structure is maintained by an |
| * updateTree() operation called when an intermediate node is |
| * required. The update operation is roughly categorized as a root |
| * update or intermediate layer update. When number of leaf nodes |
| * grow over a power of 2 then a new layer is added at the top of the |
| * tree and a new root node is initialized. The old node at the lower |
| * layer is connected to this. In an intermediate node update |
| * operation a new intermediate node is added to the required layer. |
| * |
| * Debugging: Debugging can be enabled by setting the verifyStack flag |
| * true. Debugging is implemented using a dummy stack that behaves in |
| * a naive way, using STL vectors (i.e each unique address is pushed |
| * on the top of an STL vector stack, and SD is returned as |
| * Infinity. If a non unique address is encountered then the previous |
| * entry in the STL vector is removed, all the entities above it are |
| * pushed down, and the address is pushed at the top of the stack). |
| * |
| * A printStack(int numOfEntitiesToPrint) is provided to print top n entities |
| * in both (tree and STL based dummy stack). |
| */ |
| class StackDistCalc |
| { |
| |
| private: |
| |
| struct Node; |
| |
| typedef std::map<uint64_t, Node*> IndexNodeMap; |
| typedef std::map<Addr, uint64_t> AddressIndexMap; |
| typedef std::vector<IndexNodeMap> TreeType; |
| |
| /** |
| * Gets sum from the node upwards recursively till the root. This |
| * function is called first by getSumsLeavesToRoot, and then |
| * recursively calls itself. |
| * |
| * @param node pointer to the node which is updated |
| * @param from_left variable which says that the request arrived |
| * from the left |
| * @param sum_from_below Sum of left and right children below |
| * @param level level in the tree the calling node is located |
| * @param stack_dist stack distance of the node below |
| * @return The stack distance of the current address. |
| * |
| */ |
| uint64_t getSum(Node* node, bool from_left, uint64_t sum_from_below, |
| uint64_t stack_dist, uint64_t level) const; |
| |
| /** |
| * Gets the sum from the leaf node specified. This function |
| * is called by calcStackDist. |
| * |
| * @param node pointer to the node which is updated |
| * @return The stack distance of the current address. |
| * |
| */ |
| uint64_t getSumsLeavesToRoot(Node* node) const; |
| |
| /** |
| * Updates the nodes upwards recursively till the root. |
| * This function is first called by updateSumsLeavesToRoot, |
| * and then it recursively calls itself. |
| * |
| * @param node pointer to the node which is updated |
| * @param from_left variable which says that the request arrived |
| * from the left |
| * @param sum_from_below Sum of left and right children below |
| * @param level level in the tree the calling node is located |
| * @param stack_dist stack distance of the node below |
| * @param discard_node whether the calling node was discarded or not |
| * @return The stack distance of the current address. |
| * |
| */ |
| uint64_t updateSum(Node* node, |
| bool from_left, uint64_t sum_from_below, uint64_t level, |
| uint64_t stack_dist, bool discard_node); |
| |
| /** |
| * Updates the leaf nodes and nodes above. This function is |
| * called by the calcStackDistAndUpdate. |
| * |
| * @param node pointer to the node which is updated |
| * @param is_new_leaf is true if this is a newly added node |
| * @return The stack distance of the current address. |
| * |
| */ |
| uint64_t updateSumsLeavesToRoot(Node* node, bool is_new_leaf); |
| |
| /** |
| * updateTree is a tree balancing operation, which maintains the |
| * binary tree structure. |
| * This method is called whenever index%2 == 0 (i.e. every |
| * alternate cycle) The two main operation are : |
| * OP1. Moving the root node one layer up if index counter |
| * crosses power of 2 |
| * OP2. Addition of intermediate nodes as and when required |
| * and linking them to their parents in the layer above. |
| */ |
| void updateTree(); |
| |
| /** |
| * This method is used for verification purposes |
| * It recursively traverses upwards from the given node till |
| * the root to check if the ultimate parent node (root-node) points |
| * to null. |
| * |
| * @param node pointer to the node whose sanity is being checked |
| * @param level the level at which this node is located in the tree |
| * |
| */ |
| void sanityCheckTree(const Node* node, uint64_t level = 0) const; |
| |
| /** |
| * Return the counter for address accesses (unique and |
| * non-unique). This is further used to dump stats at |
| * regular intervals. |
| * |
| * @return The stack distance of the current address. |
| */ |
| uint64_t getIndex() const { return index; } |
| |
| /** |
| * Query depth of the tree (tree[0] represents leaf layer while |
| * tree[treeDepth] represents the root layer, all layers in |
| * between contain intermediate nodes) |
| * |
| * @return Tree depth |
| */ |
| uint64_t getTreeDepth() const { return tree.size() - 1; } |
| |
| /** |
| * Print the last n items on the stack. |
| * This method prints top n entries in the tree based implementation as |
| * well as dummy stack. |
| * @param n Number of entries to print |
| */ |
| void printStack(int n = 5) const; |
| |
| /** |
| * This is an alternative implementation of the stack-distance |
| * in a naive way. It uses simple STL vector to represent the stack. |
| * It can be used in parallel for debugging purposes. |
| * It is 10x slower than the tree based implemenation. |
| * |
| * @param r_address The current address to process |
| * @param update_stack Flag to indicate if stack should be updated |
| * @return Stack distance which is calculated by this alternative |
| * implementation |
| * |
| */ |
| uint64_t verifyStackDist(const Addr r_address, |
| bool update_stack = false); |
| |
| public: |
| StackDistCalc(bool verify_stack = false); |
| |
| ~StackDistCalc(); |
| |
| /** |
| * A convenient way of refering to infinity. |
| */ |
| static constexpr uint64_t Infinity = std::numeric_limits<uint64_t>::max(); |
| |
| |
| /** |
| * Process the given address. If Mark is true then set the |
| * mark flag of the leaf node. |
| * This function returns the stack distance of the incoming |
| * address and the previous status of the mark flag. |
| * |
| * @param r_address The current address to process |
| * @param mark set the mark flag for the address. |
| * @return The stack distance of the current address and the mark flag. |
| */ |
| std::pair<uint64_t, bool> calcStackDist(const Addr r_address, |
| bool mark = false); |
| |
| /** |
| * Process the given address: |
| * - Lookup the tree for the given address |
| * - delete old node if found in tree |
| * - add a new node (if addNewNode flag is set) |
| * This function returns the stack distance of the incoming |
| * address and the status of the mark flag. |
| * |
| * @param r_address The current address to process |
| * @param addNewNode If true, a new node is added to the tree |
| * @return The stack distance of the current address and the mark flag. |
| */ |
| std::pair<uint64_t, bool> calcStackDistAndUpdate(const Addr r_address, |
| bool addNewNode = true); |
| |
| private: |
| |
| /** |
| * Node which takes form of Leaf, INode or Root |
| */ |
| struct Node |
| { |
| // Sum of the left children |
| uint64_t sumLeft; |
| |
| // Sum of the right children |
| uint64_t sumRight; |
| |
| // Flag to indicate that sumLeft has gone from non-zero value to 0 |
| bool discardLeft; |
| |
| // Flag to indicate that sumRight has gone from non-zero value to 0 |
| bool discardRight; |
| |
| // Index of the current element in the Map |
| uint64_t nodeIndex; |
| |
| // Pointer to the parent |
| Node* parent; |
| |
| // Flag to mark the node as the right/left child |
| bool isLeftNode; |
| |
| /** |
| * Flag to indicate if this address is marked. Used in case |
| * where stack distance of a touched address is required. |
| */ |
| bool isMarked; |
| |
| /** |
| * The discard flags are false by default they become true if |
| * the node is reached again in a future lookup. |
| */ |
| Node() : sumLeft(0), sumRight(0), discardLeft(false), |
| discardRight(false), nodeIndex(0), |
| parent(nullptr), isLeftNode(true), isMarked(false) |
| { } |
| }; |
| |
| /** |
| * Internal counter for address accesses (unique and non-unique) |
| * This counter increments everytime the calcStackDist() method is |
| * called. This counter is used as a key for the hash- map at the |
| * leaf layer. Practically at every call to the calculator this |
| * counter is incremented and a new leaf node is added in the tree |
| * at the leaf layer using this counter value as the key. |
| */ |
| uint64_t index; |
| |
| // Binary tree of partial sums |
| TreeType tree; |
| |
| // Hash map which returns last seen index of each address |
| AddressIndexMap aiMap; |
| |
| // Keeps count of number of the next unique index for each |
| // level in the tree |
| std::vector<uint64_t> nextIndex; |
| |
| // Dummy Stack for verification |
| std::vector<uint64_t> stack; |
| |
| // Flag to enable verification of stack. (Slows down the simulation) |
| const bool verifyStack; |
| }; |
| |
| } // namespace gem5 |
| |
| #endif //__STACK_DIST_CALC_HH__ |
