fa_lru.hh revision 12743:b5ccee582b40
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 57#include "base/bitfield.hh" 58#include "base/intmath.hh" 59#include "base/logging.hh" 60#include "base/statistics.hh" 61#include "base/types.hh" 62#include "mem/cache/blk.hh" 63#include "mem/cache/tags/base.hh" 64#include "mem/packet.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 71// A bitmask of the caches we are keeping track of. Currently the 72// lowest bit is the smallest cache we are tracking, as it is 73// specified by the corresponding parameter. The rest of the bits are 74// for exponentially growing cache sizes. 75typedef uint32_t CachesMask; 76 77/** 78 * A fully associative cache block. 79 */ 80class FALRUBlk : public CacheBlk 81{ 82 public: 83 /** The previous block in LRU order. */ 84 FALRUBlk *prev; 85 /** The next block in LRU order. */ 86 FALRUBlk *next; 87 88 /** A bit mask of the caches that fit this block. */ 89 CachesMask inCachesMask; 90}; 91 92/** 93 * A fully associative LRU cache. Keeps statistics for accesses to a number of 94 * cache sizes at once. 95 */ 96class FALRU : public BaseTags 97{ 98 public: 99 /** Typedef the block type used in this class. */ 100 typedef FALRUBlk BlkType; 101 102 protected: 103 /** The cache blocks. */ 104 FALRUBlk *blks; 105 106 /** The MRU block. */ 107 FALRUBlk *head; 108 /** The LRU block. */ 109 FALRUBlk *tail; 110 111 /** Hash table type mapping addresses to cache block pointers. */ 112 typedef std::unordered_map<Addr, FALRUBlk *, std::hash<Addr> > hash_t; 113 /** Iterator into the address hash table. */ 114 typedef hash_t::const_iterator tagIterator; 115 116 /** The address hash table. */ 117 hash_t tagHash; 118 119 /** 120 * Find the cache block for the given address. 121 * @param addr The address to find. 122 * @return The cache block of the address, if any. 123 */ 124 FALRUBlk * hashLookup(Addr addr) const; 125 126 /** 127 * Move a cache block to the MRU position. 128 * 129 * @param blk The block to promote. 130 */ 131 void moveToHead(FALRUBlk *blk); 132 133 /** 134 * Move a cache block to the LRU position. 135 * 136 * @param blk The block to demote. 137 */ 138 void moveToTail(FALRUBlk *blk); 139 140 public: 141 typedef FALRUParams Params; 142 143 /** 144 * Construct and initialize this cache tagstore. 145 */ 146 FALRU(const Params *p); 147 ~FALRU(); 148 149 /** 150 * Register the stats for this object. 151 */ 152 void regStats() override; 153 154 /** 155 * Invalidate a cache block. 156 * @param blk The block to invalidate. 157 */ 158 void invalidate(CacheBlk *blk) override; 159 160 /** 161 * Access block and update replacement data. May not succeed, in which 162 * case nullptr pointer is returned. This has all the implications of a 163 * cache access and should only be used as such. 164 * Returns the access latency and inCachesMask flags as a side effect. 165 * @param addr The address to look for. 166 * @param is_secure True if the target memory space is secure. 167 * @param lat The latency of the access. 168 * @param in_cache_mask Mask indicating the caches in which the blk fits. 169 * @return Pointer to the cache block. 170 */ 171 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat, 172 CachesMask *in_cache_mask); 173 174 /** 175 * Just a wrapper of above function to conform with the base interface. 176 */ 177 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override; 178 179 /** 180 * Find the block in the cache, do not update the replacement data. 181 * @param addr The address to look for. 182 * @param is_secure True if the target memory space is secure. 183 * @param asid The address space ID. 184 * @return Pointer to the cache block. 185 */ 186 CacheBlk* findBlock(Addr addr, bool is_secure) const override; 187 188 /** 189 * Find a block given set and way. 190 * 191 * @param set The set of the block. 192 * @param way The way of the block. 193 * @return The block. 194 */ 195 ReplaceableEntry* findBlockBySetAndWay(int set, int way) const override; 196 197 /** 198 * Find replacement victim based on address. 199 * 200 * @param addr Address to find a victim for. 201 * @return Cache block to be replaced. 202 */ 203 CacheBlk* findVictim(Addr addr) override; 204 205 /** 206 * Insert the new block into the cache and update replacement data. 207 * 208 * @param pkt Packet holding the address to update 209 * @param blk The block to update. 210 */ 211 void insertBlock(PacketPtr pkt, CacheBlk *blk) override; 212 213 /** 214 * Generate the tag from the addres. For fully associative this is just the 215 * block address. 216 * @param addr The address to get the tag from. 217 * @return The tag. 218 */ 219 Addr extractTag(Addr addr) const override 220 { 221 return blkAlign(addr); 222 } 223 224 /** 225 * Regenerate the block address from the tag. 226 * 227 * @param block The block. 228 * @return the block address. 229 */ 230 Addr regenerateBlkAddr(const CacheBlk* blk) const override 231 { 232 return blk->tag; 233 } 234 235 void forEachBlk(std::function<void(CacheBlk &)> visitor) override { 236 for (int i = 0; i < numBlocks; i++) { 237 visitor(blks[i]); 238 } 239 } 240 241 bool anyBlk(std::function<bool(CacheBlk &)> visitor) override { 242 for (int i = 0; i < numBlocks; i++) { 243 if (visitor(blks[i])) { 244 return true; 245 } 246 } 247 return false; 248 } 249 250 private: 251 /** 252 * Mechanism that allows us to simultaneously collect miss 253 * statistics for multiple caches. Currently, we keep track of 254 * caches from a set minimum size of interest up to the actual 255 * cache size. 256 */ 257 class CacheTracking 258 { 259 public: 260 CacheTracking(unsigned min_size, unsigned max_size, 261 unsigned block_size) 262 : blkSize(block_size), 263 minTrackedSize(min_size), 264 numTrackedCaches(max_size > min_size ? 265 floorLog2(max_size) - floorLog2(min_size) : 0), 266 inAllCachesMask(mask(numTrackedCaches)), 267 boundaries(new FALRUBlk *[numTrackedCaches]) 268 { 269 fatal_if(numTrackedCaches > sizeof(CachesMask) * 8, 270 "Not enough bits (%s) in type CachesMask type to keep " 271 "track of %d caches\n", sizeof(CachesMask), 272 numTrackedCaches); 273 } 274 275 ~CacheTracking() 276 { 277 delete[] boundaries; 278 } 279 280 /** 281 * Initialiaze cache blocks and the tracking mechanism 282 * 283 * All blocks in the cache need to be initialized once. 284 * 285 * @param blk the MRU block 286 * @param blk the LRU block 287 */ 288 void init(FALRUBlk *head, FALRUBlk *tail); 289 290 /** 291 * Update boundaries as a block will be moved to the MRU. 292 * 293 * For all caches that didn't fit the block before moving it, 294 * we move their boundaries one block closer to the MRU. We 295 * also update InCacheMasks as neccessary. 296 * 297 * @param blk the block that will be moved to the head 298 */ 299 void moveBlockToHead(FALRUBlk *blk); 300 301 /** 302 * Update boundaries as a block will be moved to the LRU. 303 * 304 * For all caches that fitted the block before moving it, we 305 * move their boundaries one block closer to the LRU. We 306 * also update InCacheMasks as neccessary. 307 * 308 * @param blk the block that will be moved to the head 309 */ 310 void moveBlockToTail(FALRUBlk *blk); 311 312 /** 313 * Notify of a block access. 314 * 315 * This should be called every time a block is accessed and it 316 * updates statistics. If the input block is nullptr then we 317 * treat the access as a miss. The block's InCacheMask 318 * determines the caches in which the block fits. 319 * 320 * @param blk the block to record the access for 321 */ 322 void recordAccess(FALRUBlk *blk); 323 324 /** 325 * Check that the tracking mechanism is in consistent state. 326 * 327 * Iterate from the head (MRU) to the tail (LRU) of the list 328 * of blocks and assert the inCachesMask and the boundaries 329 * are in consistent state. 330 * 331 * @param head the MRU block of the actual cache 332 * @param head the LRU block of the actual cache 333 */ 334 void check(FALRUBlk *head, FALRUBlk *tail); 335 336 /** 337 * Register the stats for this object. 338 */ 339 void regStats(std::string name); 340 341 private: 342 /** The size of the cache block */ 343 const unsigned blkSize; 344 /** The smallest cache we are tracking */ 345 const unsigned minTrackedSize; 346 /** The number of different size caches being tracked. */ 347 const int numTrackedCaches; 348 /** A mask for all cache being tracked. */ 349 const CachesMask inAllCachesMask; 350 /** Array of pointers to blocks at the cache boundaries. */ 351 FALRUBlk** boundaries; 352 353 protected: 354 /** 355 * @defgroup FALRUStats Fully Associative LRU specific statistics 356 * The FA lru stack lets us track multiple cache sizes at once. These 357 * statistics track the hits and misses for different cache sizes. 358 * @{ 359 */ 360 361 /** Hits in each cache */ 362 Stats::Vector hits; 363 /** Misses in each cache */ 364 Stats::Vector misses; 365 /** Total number of accesses */ 366 Stats::Scalar accesses; 367 368 /** 369 * @} 370 */ 371 }; 372 CacheTracking cacheTracking; 373}; 374 375#endif // __MEM_CACHE_TAGS_FA_LRU_HH__ 376