fa_lru.hh revision 12665
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 <list> 53#include <unordered_map> 54 55#include "base/intmath.hh" 56#include "mem/cache/base.hh" 57#include "mem/cache/blk.hh" 58#include "mem/cache/tags/base.hh" 59#include "mem/packet.hh" 60#include "params/FALRU.hh" 61 62// Uncomment to enable sanity checks for the FALRU cache and the 63// TrackedCaches class 64//#define FALRU_DEBUG 65 66// A bitmask of the caches we are keeping track of. Currently the 67// lowest bit is the smallest cache we are tracking, as it is 68// specified by the corresponding parameter. The rest of the bits are 69// for exponentially growing cache sizes. 70typedef uint32_t CachesMask; 71 72/** 73 * A fully associative cache block. 74 */ 75class FALRUBlk : public CacheBlk 76{ 77 public: 78 /** The previous block in LRU order. */ 79 FALRUBlk *prev; 80 /** The next block in LRU order. */ 81 FALRUBlk *next; 82 83 /** A bit mask of the caches that fit this block. */ 84 CachesMask inCachesMask; 85}; 86 87/** 88 * A fully associative LRU cache. Keeps statistics for accesses to a number of 89 * cache sizes at once. 90 */ 91class FALRU : public BaseTags 92{ 93 public: 94 /** Typedef the block type used in this class. */ 95 typedef FALRUBlk BlkType; 96 97 protected: 98 /** The cache blocks. */ 99 FALRUBlk *blks; 100 101 /** The MRU block. */ 102 FALRUBlk *head; 103 /** The LRU block. */ 104 FALRUBlk *tail; 105 106 /** Hash table type mapping addresses to cache block pointers. */ 107 typedef std::unordered_map<Addr, FALRUBlk *, std::hash<Addr> > hash_t; 108 /** Iterator into the address hash table. */ 109 typedef hash_t::const_iterator tagIterator; 110 111 /** The address hash table. */ 112 hash_t tagHash; 113 114 /** 115 * Find the cache block for the given address. 116 * @param addr The address to find. 117 * @return The cache block of the address, if any. 118 */ 119 FALRUBlk * hashLookup(Addr addr) const; 120 121 /** 122 * Move a cache block to the MRU position. 123 * 124 * @param blk The block to promote. 125 */ 126 void moveToHead(FALRUBlk *blk); 127 128 /** 129 * Move a cache block to the LRU position. 130 * 131 * @param blk The block to demote. 132 */ 133 void moveToTail(FALRUBlk *blk); 134 135 public: 136 typedef FALRUParams Params; 137 138 /** 139 * Construct and initialize this cache tagstore. 140 */ 141 FALRU(const Params *p); 142 ~FALRU(); 143 144 /** 145 * Register the stats for this object. 146 */ 147 void regStats() override; 148 149 /** 150 * Invalidate a cache block. 151 * @param blk The block to invalidate. 152 */ 153 void invalidate(CacheBlk *blk) override; 154 155 /** 156 * Access block and update replacement data. May not succeed, in which 157 * case nullptr pointer is returned. This has all the implications of a 158 * cache access and should only be used as such. 159 * Returns the access latency and inCachesMask flags as a side effect. 160 * @param addr The address to look for. 161 * @param is_secure True if the target memory space is secure. 162 * @param lat The latency of the access. 163 * @param in_cache_mask Mask indicating the caches in which the blk fits. 164 * @return Pointer to the cache block. 165 */ 166 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat, 167 CachesMask *in_cache_mask); 168 169 /** 170 * Just a wrapper of above function to conform with the base interface. 171 */ 172 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override; 173 174 /** 175 * Find the block in the cache, do not update the replacement data. 176 * @param addr The address to look for. 177 * @param is_secure True if the target memory space is secure. 178 * @param asid The address space ID. 179 * @return Pointer to the cache block. 180 */ 181 CacheBlk* findBlock(Addr addr, bool is_secure) const override; 182 183 /** 184 * Find replacement victim based on address. 185 * 186 * @param addr Address to find a victim for. 187 * @return Cache block to be replaced. 188 */ 189 CacheBlk* findVictim(Addr addr) override; 190 191 /** 192 * Insert the new block into the cache and update replacement data. 193 * 194 * @param pkt Packet holding the address to update 195 * @param blk The block to update. 196 */ 197 void insertBlock(PacketPtr pkt, CacheBlk *blk) override; 198 199 /** 200 * Find the cache block given set and way 201 * @param set The set of the block. 202 * @param way The way of the block. 203 * @return The cache block. 204 */ 205 CacheBlk* findBlockBySetAndWay(int set, int way) const override; 206 207 /** 208 * Generate the tag from the addres. For fully associative this is just the 209 * block address. 210 * @param addr The address to get the tag from. 211 * @return The tag. 212 */ 213 Addr extractTag(Addr addr) const override 214 { 215 return blkAlign(addr); 216 } 217 218 /** 219 * Return the set of an address. Only one set in a fully associative cache. 220 * @param addr The address to get the set from. 221 * @return 0. 222 */ 223 int extractSet(Addr addr) const override 224 { 225 return 0; 226 } 227 228 /** 229 * Regenerate the block address from the tag. 230 * 231 * @param block The block. 232 * @return the block address. 233 */ 234 Addr regenerateBlkAddr(const CacheBlk* blk) const override 235 { 236 return blk->tag; 237 } 238 239 /** 240 * @todo Implement as in lru. Currently not used 241 */ 242 virtual std::string print() const override { return ""; } 243 244 /** 245 * Visit each block in the tag store and apply a visitor to the 246 * block. 247 * 248 * The visitor should be a function (or object that behaves like a 249 * function) that takes a cache block reference as its parameter 250 * and returns a bool. A visitor can request the traversal to be 251 * stopped by returning false, returning true causes it to be 252 * called for the next block in the tag store. 253 * 254 * \param visitor Visitor to call on each block. 255 */ 256 void forEachBlk(CacheBlkVisitor &visitor) override { 257 for (int i = 0; i < numBlocks; i++) { 258 if (!visitor(blks[i])) 259 return; 260 } 261 } 262 263 private: 264 /** 265 * Mechanism that allows us to simultaneously collect miss 266 * statistics for multiple caches. Currently, we keep track of 267 * caches from a set minimum size of interest up to the actual 268 * cache size. 269 */ 270 class CacheTracking 271 { 272 public: 273 CacheTracking(unsigned min_size, unsigned max_size, 274 unsigned block_size) 275 : blkSize(block_size), 276 minTrackedSize(min_size), 277 numTrackedCaches(max_size > min_size ? 278 floorLog2(max_size) - floorLog2(min_size) : 0), 279 inAllCachesMask(mask(numTrackedCaches)), 280 boundaries(new FALRUBlk *[numTrackedCaches]) 281 { 282 fatal_if(numTrackedCaches > sizeof(CachesMask) * 8, 283 "Not enough bits (%s) in type CachesMask type to keep " 284 "track of %d caches\n", sizeof(CachesMask), 285 numTrackedCaches); 286 } 287 288 ~CacheTracking() 289 { 290 delete[] boundaries; 291 } 292 293 /** 294 * Initialiaze cache blocks and the tracking mechanism 295 * 296 * All blocks in the cache need to be initialized once. 297 * 298 * @param blk the MRU block 299 * @param blk the LRU block 300 */ 301 void init(FALRUBlk *head, FALRUBlk *tail); 302 303 /** 304 * Update boundaries as a block will be moved to the MRU. 305 * 306 * For all caches that didn't fit the block before moving it, 307 * we move their boundaries one block closer to the MRU. We 308 * also update InCacheMasks as neccessary. 309 * 310 * @param blk the block that will be moved to the head 311 */ 312 void moveBlockToHead(FALRUBlk *blk); 313 314 /** 315 * Update boundaries as a block will be moved to the LRU. 316 * 317 * For all caches that fitted the block before moving it, we 318 * move their boundaries one block closer to the LRU. We 319 * also update InCacheMasks as neccessary. 320 * 321 * @param blk the block that will be moved to the head 322 */ 323 void moveBlockToTail(FALRUBlk *blk); 324 325 /** 326 * Notify of a block access. 327 * 328 * This should be called every time a block is accessed and it 329 * updates statistics. If the input block is nullptr then we 330 * treat the access as a miss. The block's InCacheMask 331 * determines the caches in which the block fits. 332 * 333 * @param blk the block to record the access for 334 */ 335 void recordAccess(FALRUBlk *blk); 336 337 /** 338 * Check that the tracking mechanism is in consistent state. 339 * 340 * Iterate from the head (MRU) to the tail (LRU) of the list 341 * of blocks and assert the inCachesMask and the boundaries 342 * are in consistent state. 343 * 344 * @param head the MRU block of the actual cache 345 * @param head the LRU block of the actual cache 346 */ 347 void check(FALRUBlk *head, FALRUBlk *tail); 348 349 /** 350 * Register the stats for this object. 351 */ 352 void regStats(std::string name); 353 354 private: 355 /** The size of the cache block */ 356 const unsigned blkSize; 357 /** The smallest cache we are tracking */ 358 const unsigned minTrackedSize; 359 /** The number of different size caches being tracked. */ 360 const int numTrackedCaches; 361 /** A mask for all cache being tracked. */ 362 const CachesMask inAllCachesMask; 363 /** Array of pointers to blocks at the cache boundaries. */ 364 FALRUBlk** boundaries; 365 366 protected: 367 /** 368 * @defgroup FALRUStats Fully Associative LRU specific statistics 369 * The FA lru stack lets us track multiple cache sizes at once. These 370 * statistics track the hits and misses for different cache sizes. 371 * @{ 372 */ 373 374 /** Hits in each cache */ 375 Stats::Vector hits; 376 /** Misses in each cache */ 377 Stats::Vector misses; 378 /** Total number of accesses */ 379 Stats::Scalar accesses; 380 381 /** 382 * @} 383 */ 384 }; 385 CacheTracking cacheTracking; 386}; 387 388#endif // __MEM_CACHE_TAGS_FA_LRU_HH__ 389