1/* 2 * Copyright (c) 2012-2013,2016,2018 ARM Limited 3 * All rights reserved. 4 * 5 * The license below extends only to copyright in the software and shall 6 * not be construed as granting a license to any other intellectual 7 * property including but not limited to intellectual property relating 8 * to a hardware implementation of the functionality of the software 9 * licensed hereunder. You may use the software subject to the license 10 * terms below provided that you ensure that this notice is replicated 11 * unmodified and in its entirety in all distributions of the software, 12 * modified or unmodified, in source code or in binary form. 13 * 14 * Copyright (c) 2003-2005 The Regents of The University of Michigan 15 * All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions are 19 * met: redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer; 21 * redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution; 24 * neither the name of the copyright holders nor the names of its 25 * contributors may be used to endorse or promote products derived from 26 * this software without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 39 * 40 * Authors: Erik Hallnor 41 * Nikos Nikoleris 42 */ 43 44/** 45 * @file 46 * Declaration of a fully associative LRU tag store. 47 */ 48 49#ifndef __MEM_CACHE_TAGS_FA_LRU_HH__ 50#define __MEM_CACHE_TAGS_FA_LRU_HH__ 51 52#include <cstdint> 53#include <functional> 54#include <string> 55#include <unordered_map> 56#include <vector> 57 58#include "base/bitfield.hh" 59#include "base/intmath.hh" 60#include "base/logging.hh" 61#include "base/statistics.hh" 62#include "base/types.hh" 63#include "mem/cache/cache_blk.hh" 64#include "mem/cache/tags/base.hh" 65#include "mem/packet.hh" 66#include "params/FALRU.hh" 67 68// Uncomment to enable sanity checks for the FALRU cache and the 69// TrackedCaches class 70//#define FALRU_DEBUG 71 72class BaseCache; 73class ReplaceableEntry; 74 75// A bitmask of the caches we are keeping track of. Currently the 76// lowest bit is the smallest cache we are tracking, as it is 77// specified by the corresponding parameter. The rest of the bits are 78// for exponentially growing cache sizes. 79typedef uint32_t CachesMask; 80 81/** 82 * A fully associative cache block. 83 */ 84class FALRUBlk : public CacheBlk 85{ 86 public: 87 FALRUBlk() : CacheBlk(), prev(nullptr), next(nullptr), inCachesMask(0) {} 88 89 /** The previous block in LRU order. */ 90 FALRUBlk *prev; 91 /** The next block in LRU order. */ 92 FALRUBlk *next; 93 94 /** A bit mask of the caches that fit this block. */ 95 CachesMask inCachesMask; 96 97 /** 98 * Pretty-print inCachesMask and other CacheBlk information. 99 * 100 * @return string with basic state information 101 */ 102 std::string print() const override; 103}; 104 105/** 106 * A fully associative LRU cache. Keeps statistics for accesses to a number of 107 * cache sizes at once. 108 */ 109class FALRU : public BaseTags 110{ 111 public: 112 /** Typedef the block type used in this class. */ 113 typedef FALRUBlk BlkType; 114 115 protected: 116 /** The cache blocks. */ 117 FALRUBlk *blks; 118 119 /** The MRU block. */ 120 FALRUBlk *head; 121 /** The LRU block. */ 122 FALRUBlk *tail; 123 124 /** Hash table type mapping addresses to cache block pointers. */ 125 struct PairHash 126 { 127 template <class T1, class T2> 128 std::size_t operator()(const std::pair<T1, T2> &p) const 129 { 130 return std::hash<T1>()(p.first) ^ std::hash<T2>()(p.second); 131 } 132 }; 133 typedef std::pair<Addr, bool> TagHashKey; 134 typedef std::unordered_map<TagHashKey, FALRUBlk *, PairHash> TagHash; 135 136 /** The address hash table. */ 137 TagHash tagHash; 138 139 /** 140 * Move a cache block to the MRU position. 141 * 142 * @param blk The block to promote. 143 */ 144 void moveToHead(FALRUBlk *blk); 145 146 /** 147 * Move a cache block to the LRU position. 148 * 149 * @param blk The block to demote. 150 */ 151 void moveToTail(FALRUBlk *blk); 152 153 public: 154 typedef FALRUParams Params; 155 156 /** 157 * Construct and initialize this cache tagstore. 158 */ 159 FALRU(const Params *p); 160 ~FALRU(); 161 162 /** 163 * Initialize blocks as FALRUBlk instances. 164 */ 165 void tagsInit() override; 166 167 /** 168 * Register the stats for this object. 169 */ 170 void regStats() override; 171 172 /** 173 * Invalidate a cache block. 174 * @param blk The block to invalidate. 175 */ 176 void invalidate(CacheBlk *blk) override; 177 178 /** 179 * Access block and update replacement data. May not succeed, in which 180 * case nullptr pointer is returned. This has all the implications of a 181 * cache access and should only be used as such. 182 * Returns tag lookup latency and the inCachesMask flags as a side effect. 183 * 184 * @param addr The address to look for. 185 * @param is_secure True if the target memory space is secure. 186 * @param lat The latency of the tag lookup. 187 * @param in_cache_mask Mask indicating the caches in which the blk fits. 188 * @return Pointer to the cache block. 189 */ 190 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat, 191 CachesMask *in_cache_mask); 192 193 /** 194 * Just a wrapper of above function to conform with the base interface. 195 */ 196 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override; 197 198 /** 199 * Find the block in the cache, do not update the replacement data. 200 * @param addr The address to look for. 201 * @param is_secure True if the target memory space is secure. 202 * @param asid The address space ID. 203 * @return Pointer to the cache block. 204 */ 205 CacheBlk* findBlock(Addr addr, bool is_secure) const override; 206 207 /** 208 * Find a block given set and way. 209 * 210 * @param set The set of the block. 211 * @param way The way of the block. 212 * @return The block. 213 */ 214 ReplaceableEntry* findBlockBySetAndWay(int set, int way) const override; 215 216 /** 217 * Find replacement victim based on address. The list of evicted blocks 218 * only contains the victim. 219 * 220 * @param addr Address to find a victim for. 221 * @param is_secure True if the target memory space is secure. 222 * @param size Size, in bits, of new block to allocate. 223 * @param evict_blks Cache blocks to be evicted. 224 * @return Cache block to be replaced. 225 */ 226 CacheBlk* findVictim(Addr addr, const bool is_secure, 227 const std::size_t size, 228 std::vector<CacheBlk*>& evict_blks) const override; 229 230 /** 231 * Insert the new block into the cache and update replacement data. 232 * 233 * @param pkt Packet holding the address to update 234 * @param blk The block to update. 235 */ 236 void insertBlock(const PacketPtr pkt, CacheBlk *blk) override; 237 238 /** 239 * Generate the tag from the addres. For fully associative this is just the 240 * block address. 241 * @param addr The address to get the tag from. 242 * @return The tag. 243 */ 244 Addr extractTag(Addr addr) const override 245 { 246 return blkAlign(addr); 247 } 248 249 /** 250 * Regenerate the block address from the tag. 251 * 252 * @param block The block. 253 * @return the block address. 254 */ 255 Addr regenerateBlkAddr(const CacheBlk* blk) const override 256 { 257 return blk->tag; 258 } 259 260 void forEachBlk(std::function<void(CacheBlk &)> visitor) override { 261 for (int i = 0; i < numBlocks; i++) { 262 visitor(blks[i]); 263 } 264 } 265 266 bool anyBlk(std::function<bool(CacheBlk &)> visitor) override { 267 for (int i = 0; i < numBlocks; i++) { 268 if (visitor(blks[i])) { 269 return true; 270 } 271 } 272 return false; 273 } 274 275 private: 276 /** 277 * Mechanism that allows us to simultaneously collect miss 278 * statistics for multiple caches. Currently, we keep track of 279 * caches from a set minimum size of interest up to the actual 280 * cache size. 281 */ 282 class CacheTracking 283 { 284 public: 285 CacheTracking(unsigned min_size, unsigned max_size, 286 unsigned block_size) 287 : blkSize(block_size), 288 minTrackedSize(min_size), 289 numTrackedCaches(max_size > min_size ? 290 floorLog2(max_size) - floorLog2(min_size) : 0), 291 inAllCachesMask(mask(numTrackedCaches)), 292 boundaries(numTrackedCaches) 293 { 294 fatal_if(numTrackedCaches > sizeof(CachesMask) * 8, 295 "Not enough bits (%s) in type CachesMask type to keep " 296 "track of %d caches\n", sizeof(CachesMask), 297 numTrackedCaches); 298 } 299 300 /** 301 * Initialiaze cache blocks and the tracking mechanism 302 * 303 * All blocks in the cache need to be initialized once. 304 * 305 * @param blk the MRU block 306 * @param blk the LRU block 307 */ 308 void init(FALRUBlk *head, FALRUBlk *tail); 309 310 /** 311 * Update boundaries as a block will be moved to the MRU. 312 * 313 * For all caches that didn't fit the block before moving it, 314 * we move their boundaries one block closer to the MRU. We 315 * also update InCacheMasks as neccessary. 316 * 317 * @param blk the block that will be moved to the head 318 */ 319 void moveBlockToHead(FALRUBlk *blk); 320 321 /** 322 * Update boundaries as a block will be moved to the LRU. 323 * 324 * For all caches that fitted the block before moving it, we 325 * move their boundaries one block closer to the LRU. We 326 * also update InCacheMasks as neccessary. 327 * 328 * @param blk the block that will be moved to the head 329 */ 330 void moveBlockToTail(FALRUBlk *blk); 331 332 /** 333 * Notify of a block access. 334 * 335 * This should be called every time a block is accessed and it 336 * updates statistics. If the input block is nullptr then we 337 * treat the access as a miss. The block's InCacheMask 338 * determines the caches in which the block fits. 339 * 340 * @param blk the block to record the access for 341 */ 342 void recordAccess(FALRUBlk *blk); 343 344 /** 345 * Check that the tracking mechanism is in consistent state. 346 * 347 * Iterate from the head (MRU) to the tail (LRU) of the list 348 * of blocks and assert the inCachesMask and the boundaries 349 * are in consistent state. 350 * 351 * @param head the MRU block of the actual cache 352 * @param head the LRU block of the actual cache 353 */ 354 void check(const FALRUBlk *head, const FALRUBlk *tail) const; 355 356 /** 357 * Register the stats for this object. 358 */ 359 void regStats(std::string name); 360 361 private: 362 /** The size of the cache block */ 363 const unsigned blkSize; 364 /** The smallest cache we are tracking */ 365 const unsigned minTrackedSize; 366 /** The number of different size caches being tracked. */ 367 const int numTrackedCaches; 368 /** A mask for all cache being tracked. */ 369 const CachesMask inAllCachesMask; 370 /** Array of pointers to blocks at the cache boundaries. */ 371 std::vector<FALRUBlk*> boundaries; 372 373 protected: 374 /** 375 * @defgroup FALRUStats Fully Associative LRU specific statistics 376 * The FA lru stack lets us track multiple cache sizes at once. These 377 * statistics track the hits and misses for different cache sizes. 378 * @{ 379 */ 380 381 /** Hits in each cache */ 382 Stats::Vector hits; 383 /** Misses in each cache */ 384 Stats::Vector misses; 385 /** Total number of accesses */ 386 Stats::Scalar accesses; 387 388 /** 389 * @} 390 */ 391 }; 392 CacheTracking cacheTracking; 393}; 394 395#endif // __MEM_CACHE_TAGS_FA_LRU_HH__ 396