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 "params/FALRU.hh" 66 67// Uncomment to enable sanity checks for the FALRU cache and the 68// TrackedCaches class 69//#define FALRU_DEBUG 70 71class BaseCache; 72class ReplaceableEntry; 73 74// A bitmask of the caches we are keeping track of. Currently the 75// lowest bit is the smallest cache we are tracking, as it is 76// specified by the corresponding parameter. The rest of the bits are 77// for exponentially growing cache sizes. 78typedef uint32_t CachesMask; 79 80/** 81 * A fully associative cache block. 82 */ 83class FALRUBlk : public CacheBlk 84{ 85 public: 86 FALRUBlk() : CacheBlk(), prev(nullptr), next(nullptr), inCachesMask(0) {} 87 88 /** The previous block in LRU order. */ 89 FALRUBlk *prev; 90 /** The next block in LRU order. */ 91 FALRUBlk *next; 92 93 /** A bit mask of the caches that fit this block. */ 94 CachesMask inCachesMask; 95 96 /** 97 * Pretty-print inCachesMask and other CacheBlk information. 98 * 99 * @return string with basic state information 100 */ 101 std::string print() const override; 102}; 103 104/** 105 * A fully associative LRU cache. Keeps statistics for accesses to a number of 106 * cache sizes at once. 107 */ 108class FALRU : public BaseTags 109{ 110 public: 111 /** Typedef the block type used in this class. */ 112 typedef FALRUBlk BlkType; 113 114 protected: 115 /** The cache blocks. */ 116 FALRUBlk *blks; 117 118 /** The MRU block. */ 119 FALRUBlk *head; 120 /** The LRU block. */ 121 FALRUBlk *tail; 122 123 /** Hash table type mapping addresses to cache block pointers. */ 124 struct PairHash 125 { 126 template <class T1, class T2> 127 std::size_t operator()(const std::pair<T1, T2> &p) const 128 { 129 return std::hash<T1>()(p.first) ^ std::hash<T2>()(p.second); 130 } 131 }; 132 typedef std::pair<Addr, bool> TagHashKey; 133 typedef std::unordered_map<TagHashKey, FALRUBlk *, PairHash> TagHash; 134 135 /** The address hash table. */ 136 TagHash tagHash; 137 138 /** 139 * Move a cache block to the MRU position. 140 * 141 * @param blk The block to promote. 142 */ 143 void moveToHead(FALRUBlk *blk); 144 145 /** 146 * Move a cache block to the LRU position. 147 * 148 * @param blk The block to demote. 149 */ 150 void moveToTail(FALRUBlk *blk); 151 152 public: 153 typedef FALRUParams Params; 154 155 /** 156 * Construct and initialize this cache tagstore. 157 */ 158 FALRU(const Params *p); 159 ~FALRU(); 160 161 /**
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162 * Initialize blocks and set the parent cache back pointer.
163 *
164 * @param _cache Pointer to parent cache.
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162 * Initialize blocks as FALRUBlk instances. |
163 */
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166 void tagsInit(BaseCache *_cache) override;
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164 void tagsInit() override; |
165 166 /** 167 * Register the stats for this object. 168 */ 169 void regStats() override; 170 171 /** 172 * Invalidate a cache block. 173 * @param blk The block to invalidate. 174 */ 175 void invalidate(CacheBlk *blk) override; 176 177 /** 178 * Access block and update replacement data. May not succeed, in which 179 * case nullptr pointer is returned. This has all the implications of a 180 * cache access and should only be used as such. 181 * Returns tag lookup latency and the inCachesMask flags as a side effect. 182 * 183 * @param addr The address to look for. 184 * @param is_secure True if the target memory space is secure. 185 * @param lat The latency of the tag lookup. 186 * @param in_cache_mask Mask indicating the caches in which the blk fits. 187 * @return Pointer to the cache block. 188 */ 189 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat, 190 CachesMask *in_cache_mask); 191 192 /** 193 * Just a wrapper of above function to conform with the base interface. 194 */ 195 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override; 196 197 /** 198 * Find the block in the cache, do not update the replacement data. 199 * @param addr The address to look for. 200 * @param is_secure True if the target memory space is secure. 201 * @param asid The address space ID. 202 * @return Pointer to the cache block. 203 */ 204 CacheBlk* findBlock(Addr addr, bool is_secure) const override; 205 206 /** 207 * Find a block given set and way. 208 * 209 * @param set The set of the block. 210 * @param way The way of the block. 211 * @return The block. 212 */ 213 ReplaceableEntry* findBlockBySetAndWay(int set, int way) const override; 214 215 /** 216 * Find replacement victim based on address. The list of evicted blocks 217 * only contains the victim. 218 * 219 * @param addr Address to find a victim for. 220 * @param is_secure True if the target memory space is secure. 221 * @param evict_blks Cache blocks to be evicted. 222 * @return Cache block to be replaced. 223 */ 224 CacheBlk* findVictim(Addr addr, const bool is_secure, 225 std::vector<CacheBlk*>& evict_blks) const override; 226 227 /** 228 * Insert the new block into the cache and update replacement data. 229 * 230 * @param addr Address of the block. 231 * @param is_secure Whether the block is in secure space or not. 232 * @param src_master_ID The source requestor ID. 233 * @param task_ID The new task ID. 234 * @param blk The block to update. 235 */ 236 void insertBlock(const Addr addr, const bool is_secure, 237 const int src_master_ID, const uint32_t task_ID, 238 CacheBlk *blk) override; 239 240 /** 241 * Generate the tag from the addres. For fully associative this is just the 242 * block address. 243 * @param addr The address to get the tag from. 244 * @return The tag. 245 */ 246 Addr extractTag(Addr addr) const override 247 { 248 return blkAlign(addr); 249 } 250 251 /** 252 * Regenerate the block address from the tag. 253 * 254 * @param block The block. 255 * @return the block address. 256 */ 257 Addr regenerateBlkAddr(const CacheBlk* blk) const override 258 { 259 return blk->tag; 260 } 261 262 void forEachBlk(std::function<void(CacheBlk &)> visitor) override { 263 for (int i = 0; i < numBlocks; i++) { 264 visitor(blks[i]); 265 } 266 } 267 268 bool anyBlk(std::function<bool(CacheBlk &)> visitor) override { 269 for (int i = 0; i < numBlocks; i++) { 270 if (visitor(blks[i])) { 271 return true; 272 } 273 } 274 return false; 275 } 276 277 private: 278 /** 279 * Mechanism that allows us to simultaneously collect miss 280 * statistics for multiple caches. Currently, we keep track of 281 * caches from a set minimum size of interest up to the actual 282 * cache size. 283 */ 284 class CacheTracking 285 { 286 public: 287 CacheTracking(unsigned min_size, unsigned max_size, 288 unsigned block_size) 289 : blkSize(block_size), 290 minTrackedSize(min_size), 291 numTrackedCaches(max_size > min_size ? 292 floorLog2(max_size) - floorLog2(min_size) : 0), 293 inAllCachesMask(mask(numTrackedCaches)), 294 boundaries(numTrackedCaches) 295 { 296 fatal_if(numTrackedCaches > sizeof(CachesMask) * 8, 297 "Not enough bits (%s) in type CachesMask type to keep " 298 "track of %d caches\n", sizeof(CachesMask), 299 numTrackedCaches); 300 } 301 302 /** 303 * Initialiaze cache blocks and the tracking mechanism 304 * 305 * All blocks in the cache need to be initialized once. 306 * 307 * @param blk the MRU block 308 * @param blk the LRU block 309 */ 310 void init(FALRUBlk *head, FALRUBlk *tail); 311 312 /** 313 * Update boundaries as a block will be moved to the MRU. 314 * 315 * For all caches that didn't fit the block before moving it, 316 * we move their boundaries one block closer to the MRU. We 317 * also update InCacheMasks as neccessary. 318 * 319 * @param blk the block that will be moved to the head 320 */ 321 void moveBlockToHead(FALRUBlk *blk); 322 323 /** 324 * Update boundaries as a block will be moved to the LRU. 325 * 326 * For all caches that fitted the block before moving it, we 327 * move their boundaries one block closer to the LRU. We 328 * also update InCacheMasks as neccessary. 329 * 330 * @param blk the block that will be moved to the head 331 */ 332 void moveBlockToTail(FALRUBlk *blk); 333 334 /** 335 * Notify of a block access. 336 * 337 * This should be called every time a block is accessed and it 338 * updates statistics. If the input block is nullptr then we 339 * treat the access as a miss. The block's InCacheMask 340 * determines the caches in which the block fits. 341 * 342 * @param blk the block to record the access for 343 */ 344 void recordAccess(FALRUBlk *blk); 345 346 /** 347 * Check that the tracking mechanism is in consistent state. 348 * 349 * Iterate from the head (MRU) to the tail (LRU) of the list 350 * of blocks and assert the inCachesMask and the boundaries 351 * are in consistent state. 352 * 353 * @param head the MRU block of the actual cache 354 * @param head the LRU block of the actual cache 355 */ 356 void check(const FALRUBlk *head, const FALRUBlk *tail) const; 357 358 /** 359 * Register the stats for this object. 360 */ 361 void regStats(std::string name); 362 363 private: 364 /** The size of the cache block */ 365 const unsigned blkSize; 366 /** The smallest cache we are tracking */ 367 const unsigned minTrackedSize; 368 /** The number of different size caches being tracked. */ 369 const int numTrackedCaches; 370 /** A mask for all cache being tracked. */ 371 const CachesMask inAllCachesMask; 372 /** Array of pointers to blocks at the cache boundaries. */ 373 std::vector<FALRUBlk*> boundaries; 374 375 protected: 376 /** 377 * @defgroup FALRUStats Fully Associative LRU specific statistics 378 * The FA lru stack lets us track multiple cache sizes at once. These 379 * statistics track the hits and misses for different cache sizes. 380 * @{ 381 */ 382 383 /** Hits in each cache */ 384 Stats::Vector hits; 385 /** Misses in each cache */ 386 Stats::Vector misses; 387 /** Total number of accesses */ 388 Stats::Scalar accesses; 389 390 /** 391 * @} 392 */ 393 }; 394 CacheTracking cacheTracking; 395}; 396 397#endif // __MEM_CACHE_TAGS_FA_LRU_HH__
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