fa_lru.cc revision 13225:8d1621fc586e
1/* 2 * Copyright (c) 2018 Inria 3 * Copyright (c) 2013,2016-2018 ARM Limited 4 * All rights reserved. 5 * 6 * The license below extends only to copyright in the software and shall 7 * not be construed as granting a license to any other intellectual 8 * property including but not limited to intellectual property relating 9 * to a hardware implementation of the functionality of the software 10 * licensed hereunder. You may use the software subject to the license 11 * terms below provided that you ensure that this notice is replicated 12 * unmodified and in its entirety in all distributions of the software, 13 * modified or unmodified, in source code or in binary form. 14 * 15 * Copyright (c) 2003-2005 The Regents of The University of Michigan 16 * All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions are 20 * met: redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer; 22 * redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution; 25 * neither the name of the copyright holders nor the names of its 26 * contributors may be used to endorse or promote products derived from 27 * this software without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 40 * 41 * Authors: Erik Hallnor 42 * Nikos Nikoleris 43 * Daniel Carvalho 44 */ 45 46/** 47 * @file 48 * Definitions a fully associative LRU tagstore. 49 */ 50 51#include "mem/cache/tags/fa_lru.hh" 52 53#include <cassert> 54#include <sstream> 55 56#include "base/intmath.hh" 57#include "base/logging.hh" 58#include "mem/cache/base.hh" 59#include "mem/cache/replacement_policies/replaceable_entry.hh" 60 61std::string 62FALRUBlk::print() const 63{ 64 return csprintf("%s inCachesMask: %#x", CacheBlk::print(), inCachesMask); 65} 66 67FALRU::FALRU(const Params *p) 68 : BaseTags(p), 69 70 cacheTracking(p->min_tracked_cache_size, size, blkSize) 71{ 72 if (!isPowerOf2(blkSize)) 73 fatal("cache block size (in bytes) `%d' must be a power of two", 74 blkSize); 75 if (!isPowerOf2(size)) 76 fatal("Cache Size must be power of 2 for now"); 77 78 blks = new FALRUBlk[numBlocks]; 79} 80 81FALRU::~FALRU() 82{ 83 delete[] blks; 84} 85 86void 87FALRU::init(BaseCache* cache) 88{ 89 // Set parent cache 90 setCache(cache); 91 92 head = &(blks[0]); 93 head->prev = nullptr; 94 head->next = &(blks[1]); 95 head->setPosition(0, 0); 96 head->data = &dataBlks[0]; 97 98 for (unsigned i = 1; i < numBlocks - 1; i++) { 99 blks[i].prev = &(blks[i-1]); 100 blks[i].next = &(blks[i+1]); 101 blks[i].setPosition(0, i); 102 103 // Associate a data chunk to the block 104 blks[i].data = &dataBlks[blkSize*i]; 105 } 106 107 tail = &(blks[numBlocks - 1]); 108 tail->prev = &(blks[numBlocks - 2]); 109 tail->next = nullptr; 110 tail->setPosition(0, numBlocks - 1); 111 tail->data = &dataBlks[(numBlocks - 1) * blkSize]; 112 113 cacheTracking.init(head, tail); 114} 115 116void 117FALRU::regStats() 118{ 119 BaseTags::regStats(); 120 cacheTracking.regStats(name()); 121} 122 123void 124FALRU::invalidate(CacheBlk *blk) 125{ 126 // Erase block entry reference in the hash table 127 auto num_erased = tagHash.erase(std::make_pair(blk->tag, blk->isSecure())); 128 129 // Sanity check; only one block reference should be erased 130 assert(num_erased == 1); 131 132 // Invalidate block entry. Must be done after the hash is erased 133 BaseTags::invalidate(blk); 134 135 // Decrease the number of tags in use 136 tagsInUse--; 137 138 // Move the block to the tail to make it the next victim 139 moveToTail((FALRUBlk*)blk); 140} 141 142CacheBlk* 143FALRU::accessBlock(Addr addr, bool is_secure, Cycles &lat) 144{ 145 return accessBlock(addr, is_secure, lat, 0); 146} 147 148CacheBlk* 149FALRU::accessBlock(Addr addr, bool is_secure, Cycles &lat, 150 CachesMask *in_caches_mask) 151{ 152 CachesMask mask = 0; 153 FALRUBlk* blk = static_cast<FALRUBlk*>(findBlock(addr, is_secure)); 154 155 if (blk && blk->isValid()) { 156 // If a cache hit 157 lat = accessLatency; 158 // Check if the block to be accessed is available. If not, 159 // apply the accessLatency on top of block->whenReady. 160 if (blk->whenReady > curTick() && 161 cache->ticksToCycles(blk->whenReady - curTick()) > 162 accessLatency) { 163 lat = cache->ticksToCycles(blk->whenReady - curTick()) + 164 accessLatency; 165 } 166 mask = blk->inCachesMask; 167 168 moveToHead(blk); 169 } else { 170 // If a cache miss 171 lat = lookupLatency; 172 } 173 if (in_caches_mask) { 174 *in_caches_mask = mask; 175 } 176 177 cacheTracking.recordAccess(blk); 178 179 return blk; 180} 181 182CacheBlk* 183FALRU::findBlock(Addr addr, bool is_secure) const 184{ 185 FALRUBlk* blk = nullptr; 186 187 Addr tag = extractTag(addr); 188 auto iter = tagHash.find(std::make_pair(tag, is_secure)); 189 if (iter != tagHash.end()) { 190 blk = (*iter).second; 191 } 192 193 if (blk && blk->isValid()) { 194 assert(blk->tag == tag); 195 assert(blk->isSecure() == is_secure); 196 } 197 198 return blk; 199} 200 201ReplaceableEntry* 202FALRU::findBlockBySetAndWay(int set, int way) const 203{ 204 assert(set == 0); 205 return &blks[way]; 206} 207 208CacheBlk* 209FALRU::findVictim(Addr addr, const bool is_secure, 210 std::vector<CacheBlk*>& evict_blks) const 211{ 212 // The victim is always stored on the tail for the FALRU 213 FALRUBlk* victim = tail; 214 215 // There is only one eviction for this replacement 216 evict_blks.push_back(victim); 217 218 return victim; 219} 220 221void 222FALRU::insertBlock(const Addr addr, const bool is_secure, 223 const int src_master_ID, const uint32_t task_ID, 224 CacheBlk *blk) 225{ 226 FALRUBlk* falruBlk = static_cast<FALRUBlk*>(blk); 227 228 // Make sure block is not present in the cache 229 assert(falruBlk->inCachesMask == 0); 230 231 // Do common block insertion functionality 232 BaseTags::insertBlock(addr, is_secure, src_master_ID, task_ID, blk); 233 234 // Increment tag counter 235 tagsInUse++; 236 237 // New block is the MRU 238 moveToHead(falruBlk); 239 240 // Insert new block in the hash table 241 tagHash[std::make_pair(blk->tag, blk->isSecure())] = falruBlk; 242} 243 244void 245FALRU::moveToHead(FALRUBlk *blk) 246{ 247 // If block is not already head, do the moving 248 if (blk != head) { 249 cacheTracking.moveBlockToHead(blk); 250 // If block is tail, set previous block as new tail 251 if (blk == tail){ 252 assert(blk->next == nullptr); 253 tail = blk->prev; 254 tail->next = nullptr; 255 // Inform block's surrounding blocks that it has been moved 256 } else { 257 blk->prev->next = blk->next; 258 blk->next->prev = blk->prev; 259 } 260 261 // Swap pointers 262 blk->next = head; 263 blk->prev = nullptr; 264 head->prev = blk; 265 head = blk; 266 267 cacheTracking.check(head, tail); 268 } 269} 270 271void 272FALRU::moveToTail(FALRUBlk *blk) 273{ 274 // If block is not already tail, do the moving 275 if (blk != tail) { 276 cacheTracking.moveBlockToTail(blk); 277 // If block is head, set next block as new head 278 if (blk == head){ 279 assert(blk->prev == nullptr); 280 head = blk->next; 281 head->prev = nullptr; 282 // Inform block's surrounding blocks that it has been moved 283 } else { 284 blk->prev->next = blk->next; 285 blk->next->prev = blk->prev; 286 } 287 288 // Swap pointers 289 blk->prev = tail; 290 blk->next = nullptr; 291 tail->next = blk; 292 tail = blk; 293 294 cacheTracking.check(head, tail); 295 } 296} 297 298FALRU * 299FALRUParams::create() 300{ 301 return new FALRU(this); 302} 303 304void 305FALRU::CacheTracking::check(const FALRUBlk *head, const FALRUBlk *tail) const 306{ 307#ifdef FALRU_DEBUG 308 const FALRUBlk* blk = head; 309 unsigned curr_size = 0; 310 unsigned tracked_cache_size = minTrackedSize; 311 CachesMask in_caches_mask = inAllCachesMask; 312 int j = 0; 313 314 while (blk) { 315 panic_if(blk->inCachesMask != in_caches_mask, "Expected cache mask " 316 "%x found %x", blk->inCachesMask, in_caches_mask); 317 318 curr_size += blkSize; 319 if (curr_size == tracked_cache_size && blk != tail) { 320 panic_if(boundaries[j] != blk, "Unexpected boundary for the %d-th " 321 "cache", j); 322 tracked_cache_size <<= 1; 323 // from this point, blocks fit only in the larger caches 324 in_caches_mask &= ~(1U << j); 325 ++j; 326 } 327 blk = blk->next; 328 } 329#endif // FALRU_DEBUG 330} 331 332void 333FALRU::CacheTracking::init(FALRUBlk *head, FALRUBlk *tail) 334{ 335 // early exit if we are not tracking any extra caches 336 FALRUBlk* blk = numTrackedCaches ? head : nullptr; 337 unsigned curr_size = 0; 338 unsigned tracked_cache_size = minTrackedSize; 339 CachesMask in_caches_mask = inAllCachesMask; 340 int j = 0; 341 342 while (blk) { 343 blk->inCachesMask = in_caches_mask; 344 345 curr_size += blkSize; 346 if (curr_size == tracked_cache_size && blk != tail) { 347 boundaries[j] = blk; 348 349 tracked_cache_size <<= 1; 350 // from this point, blocks fit only in the larger caches 351 in_caches_mask &= ~(1U << j); 352 ++j; 353 } 354 blk = blk->next; 355 } 356} 357 358 359void 360FALRU::CacheTracking::moveBlockToHead(FALRUBlk *blk) 361{ 362 // Get the mask of all caches, in which the block didn't fit 363 // before moving it to the head 364 CachesMask update_caches_mask = inAllCachesMask ^ blk->inCachesMask; 365 366 for (int i = 0; i < numTrackedCaches; i++) { 367 CachesMask current_cache_mask = 1U << i; 368 if (current_cache_mask & update_caches_mask) { 369 // if the ith cache didn't fit the block (before it is moved to 370 // the head), move the ith boundary 1 block closer to the 371 // MRU 372 boundaries[i]->inCachesMask &= ~current_cache_mask; 373 boundaries[i] = boundaries[i]->prev; 374 } else if (boundaries[i] == blk) { 375 // Make sure the boundary doesn't point to the block 376 // we are about to move 377 boundaries[i] = blk->prev; 378 } 379 } 380 381 // Make block reside in all caches 382 blk->inCachesMask = inAllCachesMask; 383} 384 385void 386FALRU::CacheTracking::moveBlockToTail(FALRUBlk *blk) 387{ 388 CachesMask update_caches_mask = blk->inCachesMask; 389 390 for (int i = 0; i < numTrackedCaches; i++) { 391 CachesMask current_cache_mask = 1U << i; 392 if (current_cache_mask & update_caches_mask) { 393 // if the ith cache fitted the block (before it is moved to 394 // the tail), move the ith boundary 1 block closer to the 395 // LRU 396 boundaries[i] = boundaries[i]->next; 397 if (boundaries[i] == blk) { 398 // Make sure the boundary doesn't point to the block 399 // we are about to move 400 boundaries[i] = blk->next; 401 } 402 boundaries[i]->inCachesMask |= current_cache_mask; 403 } 404 } 405 406 // The block now fits only in the actual cache 407 blk->inCachesMask = 0; 408} 409 410void 411FALRU::CacheTracking::recordAccess(FALRUBlk *blk) 412{ 413 for (int i = 0; i < numTrackedCaches; i++) { 414 if (blk && ((1U << i) & blk->inCachesMask)) { 415 hits[i]++; 416 } else { 417 misses[i]++; 418 } 419 } 420 421 // Record stats for the actual cache too 422 if (blk && blk->isValid()) { 423 hits[numTrackedCaches]++; 424 } else { 425 misses[numTrackedCaches]++; 426 } 427 428 accesses++; 429} 430 431void 432printSize(std::ostream &stream, size_t size) 433{ 434 static const char *SIZES[] = { "B", "kB", "MB", "GB", "TB", "ZB" }; 435 int div = 0; 436 while (size >= 1024 && div < (sizeof SIZES / sizeof *SIZES)) { 437 div++; 438 size >>= 10; 439 } 440 stream << size << SIZES[div]; 441} 442 443void 444FALRU::CacheTracking::regStats(std::string name) 445{ 446 hits 447 .init(numTrackedCaches + 1) 448 .name(name + ".falru_hits") 449 .desc("The number of hits in each cache size.") 450 ; 451 misses 452 .init(numTrackedCaches + 1) 453 .name(name + ".falru_misses") 454 .desc("The number of misses in each cache size.") 455 ; 456 accesses 457 .name(name + ".falru_accesses") 458 .desc("The number of accesses to the FA LRU cache.") 459 ; 460 461 for (unsigned i = 0; i < numTrackedCaches + 1; ++i) { 462 std::stringstream size_str; 463 printSize(size_str, minTrackedSize << i); 464 hits.subname(i, size_str.str()); 465 hits.subdesc(i, "Hits in a " + size_str.str() + " cache"); 466 misses.subname(i, size_str.str()); 467 misses.subdesc(i, "Misses in a " + size_str.str() + " cache"); 468 } 469} 470