1/* 2 * Copyright (c) 2018 Inria 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 * Authors: Daniel Carvalho 29 */ 30 31/** 32 * @file 33 * Declaration of a compressed set associative tag store using superblocks. 34 */ 35 36#ifndef __MEM_CACHE_TAGS_COMPRESSED_TAGS_HH__ 37#define __MEM_CACHE_TAGS_COMPRESSED_TAGS_HH__ 38 39#include <vector> 40 41#include "mem/cache/tags/sector_tags.hh" 42#include "mem/cache/tags/super_blk.hh" 43 44class BaseCache;
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45class CacheBlk; |
46struct CompressedTagsParams; 47 48/** 49 * A CompressedTags cache tag store. 50 * @sa \ref gem5MemorySystem "gem5 Memory System" 51 * 52 * The Compression Ratio (CR) of a superblock is defined by 53 * CR = uncompressed_size / compressed_size. 54 * 55 * The CompressedTags placement policy divides the cache into s sets of w 56 * superblocks (ways). Each superblock can then contain up to CR compressed 57 * blocks. 58 * 59 * For each tag entry there can be multiple data blocks. We have the same 60 * number of tags a conventional cache would have, but we instantiate the 61 * maximum number of data blocks (according to the compression ratio) per 62 * tag, to virtually implement compression without increasing the complexity 63 * of the simulator. 64 * 65 * This is a simple implementation of cache compression, where superblocks 66 * can only have at most numBlocksPerSector compressed blocks, each compressed 67 * to at least (100/numBlocksPerSector)% of its size. 68 * 69 * numBlocksPerSector holds the maximum number of blocks a superblock with 70 * the best possible compression factor would hold. It is equivalent to CR 71 * from the previous definition. 72 */ 73class CompressedTags : public SectorTags 74{ 75 private: 76 /** The cache blocks. */ 77 std::vector<CompressionBlk> blks; 78 /** The cache superblocks. */ 79 std::vector<SuperBlk> superBlks; 80 81 public: 82 /** Convenience typedef. */ 83 typedef CompressedTagsParams Params; 84 85 /** 86 * Construct and initialize this tag store. 87 */ 88 CompressedTags(const Params *p); 89 90 /** 91 * Destructor. 92 */ 93 virtual ~CompressedTags() {}; 94 95 /** 96 * Initialize blocks as SuperBlk and CompressionBlk instances. 97 */ 98 void tagsInit() override; 99 100 /**
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101 * Checks whether a superblock can co-allocate given compressed data block. 102 * 103 * @param superblock Superblock to check. 104 * @param compressed_size Size, in bits, of new block to allocate. 105 * @return True if block can be co-allocated in superblock. 106 */ 107 bool canCoAllocate(const SuperBlk* superblock, 108 const std::size_t compressed_size) const; 109 110 /** 111 * Find replacement victim based on address. Checks if data can be co- 112 * allocated before choosing blocks to be evicted. 113 * 114 * @param addr Address to find a victim for. 115 * @param is_secure True if the target memory space is secure. 116 * @param compressed_size Size, in bits, of new block to allocate. 117 * @param evict_blks Cache blocks to be evicted. 118 * @return Cache block to be replaced. 119 */ 120 CacheBlk* findVictim(Addr addr, const bool is_secure, 121 const std::size_t compressed_size, 122 std::vector<CacheBlk*>& evict_blks) const override; 123 124 /** |
125 * Insert the new block into the cache and update replacement data. 126 * 127 * @param pkt Packet holding the address to update 128 * @param blk The block to update. 129 */ 130 void insertBlock(const PacketPtr pkt, CacheBlk *blk) override; 131 132 /** 133 * Visit each sub-block in the tags and apply a visitor. 134 * 135 * The visitor should be a std::function that takes a cache block. 136 * reference as its parameter. 137 * 138 * @param visitor Visitor to call on each block. 139 */ 140 void forEachBlk(std::function<void(CacheBlk &)> visitor) override; 141 142 /** 143 * Find if any of the sub-blocks satisfies a condition. 144 * 145 * The visitor should be a std::function that takes a cache block 146 * reference as its parameter. The visitor will terminate the 147 * traversal early if the condition is satisfied. 148 * 149 * @param visitor Visitor to call on each block. 150 */ 151 bool anyBlk(std::function<bool(CacheBlk &)> visitor) override; 152}; 153 154#endif //__MEM_CACHE_TAGS_COMPRESSED_TAGS_HH__
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