fa_lru.cc revision 12665:4ca9fc117b95
1/* 2 * Copyright (c) 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 * Definitions a fully associative LRU tagstore. 47 */ 48 49#include "mem/cache/tags/fa_lru.hh" 50 51#include <cassert> 52#include <sstream> 53 54#include "base/intmath.hh" 55#include "base/logging.hh" 56 57FALRU::FALRU(const Params *p) 58 : BaseTags(p), 59 60 cacheTracking(p->min_tracked_cache_size, size, blkSize) 61{ 62 if (!isPowerOf2(blkSize)) 63 fatal("cache block size (in bytes) `%d' must be a power of two", 64 blkSize); 65 if (!isPowerOf2(size)) 66 fatal("Cache Size must be power of 2 for now"); 67 68 blks = new FALRUBlk[numBlocks]; 69 70 head = &(blks[0]); 71 head->prev = nullptr; 72 head->next = &(blks[1]); 73 head->set = 0; 74 head->way = 0; 75 head->data = &dataBlks[0]; 76 77 for (unsigned i = 1; i < numBlocks - 1; i++) { 78 blks[i].prev = &(blks[i-1]); 79 blks[i].next = &(blks[i+1]); 80 blks[i].set = 0; 81 blks[i].way = i; 82 83 // Associate a data chunk to the block 84 blks[i].data = &dataBlks[blkSize*i]; 85 } 86 87 tail = &(blks[numBlocks - 1]); 88 tail->prev = &(blks[numBlocks - 2]); 89 tail->next = nullptr; 90 tail->set = 0; 91 tail->way = numBlocks - 1; 92 tail->data = &dataBlks[(numBlocks - 1) * blkSize]; 93 94 cacheTracking.init(head, tail); 95} 96 97FALRU::~FALRU() 98{ 99 delete[] blks; 100} 101 102void 103FALRU::regStats() 104{ 105 BaseTags::regStats(); 106 cacheTracking.regStats(name()); 107} 108 109FALRUBlk * 110FALRU::hashLookup(Addr addr) const 111{ 112 tagIterator iter = tagHash.find(addr); 113 if (iter != tagHash.end()) { 114 return (*iter).second; 115 } 116 return nullptr; 117} 118 119void 120FALRU::invalidate(CacheBlk *blk) 121{ 122 BaseTags::invalidate(blk); 123 124 // Move the block to the tail to make it the next victim 125 moveToTail((FALRUBlk*)blk); 126 127 // Erase block entry in the hash table 128 tagHash.erase(blk->tag); 129} 130 131CacheBlk* 132FALRU::accessBlock(Addr addr, bool is_secure, Cycles &lat) 133{ 134 return accessBlock(addr, is_secure, lat, 0); 135} 136 137CacheBlk* 138FALRU::accessBlock(Addr addr, bool is_secure, Cycles &lat, 139 CachesMask *in_caches_mask) 140{ 141 CachesMask mask = 0; 142 Addr blkAddr = blkAlign(addr); 143 FALRUBlk* blk = hashLookup(blkAddr); 144 145 if (blk && blk->isValid()) { 146 // If a cache hit 147 lat = accessLatency; 148 // Check if the block to be accessed is available. If not, 149 // apply the accessLatency on top of block->whenReady. 150 if (blk->whenReady > curTick() && 151 cache->ticksToCycles(blk->whenReady - curTick()) > 152 accessLatency) { 153 lat = cache->ticksToCycles(blk->whenReady - curTick()) + 154 accessLatency; 155 } 156 assert(blk->tag == blkAddr); 157 mask = blk->inCachesMask; 158 moveToHead(blk); 159 } else { 160 // If a cache miss 161 lat = lookupLatency; 162 blk = nullptr; 163 } 164 if (in_caches_mask) { 165 *in_caches_mask = mask; 166 } 167 168 cacheTracking.recordAccess(blk); 169 170 return blk; 171} 172 173 174CacheBlk* 175FALRU::findBlock(Addr addr, bool is_secure) const 176{ 177 Addr blkAddr = blkAlign(addr); 178 FALRUBlk* blk = hashLookup(blkAddr); 179 180 if (blk && blk->isValid()) { 181 assert(blk->tag == blkAddr); 182 } else { 183 blk = nullptr; 184 } 185 return blk; 186} 187 188CacheBlk* 189FALRU::findBlockBySetAndWay(int set, int way) const 190{ 191 assert(set == 0); 192 return &blks[way]; 193} 194 195CacheBlk* 196FALRU::findVictim(Addr addr) 197{ 198 return tail; 199} 200 201void 202FALRU::insertBlock(PacketPtr pkt, CacheBlk *blk) 203{ 204 FALRUBlk* falruBlk = static_cast<FALRUBlk*>(blk); 205 206 // Make sure block is not present in the cache 207 assert(falruBlk->inCachesMask == 0); 208 209 // Do common block insertion functionality 210 BaseTags::insertBlock(pkt, blk); 211 212 // New block is the MRU 213 moveToHead(falruBlk); 214 215 // Insert new block in the hash table 216 tagHash[falruBlk->tag] = falruBlk; 217} 218 219void 220FALRU::moveToHead(FALRUBlk *blk) 221{ 222 // If block is not already head, do the moving 223 if (blk != head) { 224 cacheTracking.moveBlockToHead(blk); 225 // If block is tail, set previous block as new tail 226 if (blk == tail){ 227 assert(blk->next == nullptr); 228 tail = blk->prev; 229 tail->next = nullptr; 230 // Inform block's surrounding blocks that it has been moved 231 } else { 232 blk->prev->next = blk->next; 233 blk->next->prev = blk->prev; 234 } 235 236 // Swap pointers 237 blk->next = head; 238 blk->prev = nullptr; 239 head->prev = blk; 240 head = blk; 241 242 cacheTracking.check(head, tail); 243 } 244} 245 246void 247FALRU::moveToTail(FALRUBlk *blk) 248{ 249 // If block is not already tail, do the moving 250 if (blk != tail) { 251 cacheTracking.moveBlockToTail(blk); 252 // If block is head, set next block as new head 253 if (blk == head){ 254 assert(blk->prev == nullptr); 255 head = blk->next; 256 head->prev = nullptr; 257 // Inform block's surrounding blocks that it has been moved 258 } else { 259 blk->prev->next = blk->next; 260 blk->next->prev = blk->prev; 261 } 262 263 // Swap pointers 264 blk->prev = tail; 265 blk->next = nullptr; 266 tail->next = blk; 267 tail = blk; 268 269 cacheTracking.check(head, tail); 270 } 271} 272 273FALRU * 274FALRUParams::create() 275{ 276 return new FALRU(this); 277} 278 279void 280FALRU::CacheTracking::check(FALRUBlk *head, FALRUBlk *tail) 281{ 282#ifdef FALRU_DEBUG 283 FALRUBlk* blk = head; 284 unsigned curr_size = 0; 285 unsigned tracked_cache_size = minTrackedSize; 286 CachesMask in_caches_mask = inAllCachesMask; 287 int j = 0; 288 289 while (blk) { 290 panic_if(blk->inCachesMask != in_caches_mask, "Expected cache mask " 291 "%x found %x", blk->inCachesMask, in_caches_mask); 292 293 curr_size += blkSize; 294 if (curr_size == tracked_cache_size && blk != tail) { 295 panic_if(boundaries[j] != blk, "Unexpected boundary for the %d-th " 296 "cache", j); 297 tracked_cache_size <<= 1; 298 // from this point, blocks fit only in the larger caches 299 in_caches_mask &= ~(1U << j); 300 ++j; 301 } 302 blk = blk->next; 303 } 304#endif // FALRU_DEBUG 305} 306 307void 308FALRU::CacheTracking::init(FALRUBlk *head, FALRUBlk *tail) 309{ 310 // early exit if we are not tracking any extra caches 311 FALRUBlk* blk = numTrackedCaches ? head : nullptr; 312 unsigned curr_size = 0; 313 unsigned tracked_cache_size = minTrackedSize; 314 CachesMask in_caches_mask = inAllCachesMask; 315 int j = 0; 316 317 while (blk) { 318 blk->inCachesMask = in_caches_mask; 319 320 curr_size += blkSize; 321 if (curr_size == tracked_cache_size && blk != tail) { 322 boundaries[j] = blk; 323 324 tracked_cache_size <<= 1; 325 // from this point, blocks fit only in the larger caches 326 in_caches_mask &= ~(1U << j); 327 ++j; 328 } 329 blk = blk->next; 330 } 331} 332 333 334void 335FALRU::CacheTracking::moveBlockToHead(FALRUBlk *blk) 336{ 337 // Get the mask of all caches, in which the block didn't fit 338 // before moving it to the head 339 CachesMask update_caches_mask = inAllCachesMask ^ blk->inCachesMask; 340 341 for (int i = 0; i < numTrackedCaches; i++) { 342 CachesMask current_cache_mask = 1U << i; 343 if (current_cache_mask & update_caches_mask) { 344 // if the ith cache didn't fit the block (before it is moved to 345 // the head), move the ith boundary 1 block closer to the 346 // MRU 347 boundaries[i]->inCachesMask &= ~current_cache_mask; 348 boundaries[i] = boundaries[i]->prev; 349 } else if (boundaries[i] == blk) { 350 // Make sure the boundary doesn't point to the block 351 // we are about to move 352 boundaries[i] = blk->prev; 353 } 354 } 355 356 // Make block reside in all caches 357 blk->inCachesMask = inAllCachesMask; 358} 359 360void 361FALRU::CacheTracking::moveBlockToTail(FALRUBlk *blk) 362{ 363 CachesMask update_caches_mask = blk->inCachesMask; 364 365 for (int i = 0; i < numTrackedCaches; i++) { 366 CachesMask current_cache_mask = 1U << i; 367 if (current_cache_mask & update_caches_mask) { 368 // if the ith cache fitted the block (before it is moved to 369 // the tail), move the ith boundary 1 block closer to the 370 // LRU 371 boundaries[i] = boundaries[i]->next; 372 if (boundaries[i] == blk) { 373 // Make sure the boundary doesn't point to the block 374 // we are about to move 375 boundaries[i] = blk->next; 376 } 377 boundaries[i]->inCachesMask |= current_cache_mask; 378 } 379 } 380 381 // The block now fits only in the actual cache 382 blk->inCachesMask = 0; 383} 384 385void 386FALRU::CacheTracking::recordAccess(FALRUBlk *blk) 387{ 388 for (int i = 0; i < numTrackedCaches; i++) { 389 if (blk && ((1U << i) & blk->inCachesMask)) { 390 hits[i]++; 391 } else { 392 misses[i]++; 393 } 394 } 395 396 // Record stats for the actual cache too 397 if (blk) { 398 hits[numTrackedCaches]++; 399 } else { 400 misses[numTrackedCaches]++; 401 } 402 403 accesses++; 404} 405 406void 407printSize(std::ostream &stream, size_t size) 408{ 409 static const char *SIZES[] = { "B", "kB", "MB", "GB", "TB", "ZB" }; 410 int div = 0; 411 while (size >= 1024 && div < (sizeof SIZES / sizeof *SIZES)) { 412 div++; 413 size >>= 10; 414 } 415 stream << size << SIZES[div]; 416} 417 418void 419FALRU::CacheTracking::regStats(std::string name) 420{ 421 hits 422 .init(numTrackedCaches + 1) 423 .name(name + ".falru_hits") 424 .desc("The number of hits in each cache size.") 425 ; 426 misses 427 .init(numTrackedCaches + 1) 428 .name(name + ".falru_misses") 429 .desc("The number of misses in each cache size.") 430 ; 431 accesses 432 .name(name + ".falru_accesses") 433 .desc("The number of accesses to the FA LRU cache.") 434 ; 435 436 for (unsigned i = 0; i < numTrackedCaches + 1; ++i) { 437 std::stringstream size_str; 438 printSize(size_str, minTrackedSize << i); 439 hits.subname(i, size_str.str()); 440 hits.subdesc(i, "Hits in a " + size_str.str() + " cache"); 441 misses.subname(i, size_str.str()); 442 misses.subdesc(i, "Misses in a " + size_str.str() + " cache"); 443 } 444} 445