base_set_assoc.hh revision 11722:f15f02d8c79e
1/* 2 * Copyright (c) 2012-2014 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) 2003-2005,2014 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 */ 42 43/** 44 * @file 45 * Declaration of a base set associative tag store. 46 */ 47 48#ifndef __MEM_CACHE_TAGS_BASESETASSOC_HH__ 49#define __MEM_CACHE_TAGS_BASESETASSOC_HH__ 50 51#include <cassert> 52#include <cstring> 53#include <list> 54 55#include "mem/cache/base.hh" 56#include "mem/cache/blk.hh" 57#include "mem/cache/tags/base.hh" 58#include "mem/cache/tags/cacheset.hh" 59#include "mem/packet.hh" 60#include "params/BaseSetAssoc.hh" 61 62/** 63 * A BaseSetAssoc cache tag store. 64 * @sa \ref gem5MemorySystem "gem5 Memory System" 65 * 66 * The BaseSetAssoc tags provide a base, as well as the functionality 67 * common to any set associative tags. Any derived class must implement 68 * the methods related to the specifics of the actual replacment policy. 69 * These are: 70 * 71 * BlkType* accessBlock(); 72 * BlkType* findVictim(); 73 * void insertBlock(); 74 * void invalidate(); 75 */ 76class BaseSetAssoc : public BaseTags 77{ 78 public: 79 /** Typedef the block type used in this tag store. */ 80 typedef CacheBlk BlkType; 81 /** Typedef for a list of pointers to the local block class. */ 82 typedef std::list<BlkType*> BlkList; 83 /** Typedef the set type used in this tag store. */ 84 typedef CacheSet<CacheBlk> SetType; 85 86 87 protected: 88 /** The associativity of the cache. */ 89 const unsigned assoc; 90 /** The allocatable associativity of the cache (alloc mask). */ 91 unsigned allocAssoc; 92 /** The number of sets in the cache. */ 93 const unsigned numSets; 94 /** Whether tags and data are accessed sequentially. */ 95 const bool sequentialAccess; 96 97 /** The cache sets. */ 98 SetType *sets; 99 100 /** The cache blocks. */ 101 BlkType *blks; 102 /** The data blocks, 1 per cache block. */ 103 uint8_t *dataBlks; 104 105 /** The amount to shift the address to get the set. */ 106 int setShift; 107 /** The amount to shift the address to get the tag. */ 108 int tagShift; 109 /** Mask out all bits that aren't part of the set index. */ 110 unsigned setMask; 111 /** Mask out all bits that aren't part of the block offset. */ 112 unsigned blkMask; 113 114public: 115 116 /** Convenience typedef. */ 117 typedef BaseSetAssocParams Params; 118 119 /** 120 * Construct and initialize this tag store. 121 */ 122 BaseSetAssoc(const Params *p); 123 124 /** 125 * Destructor 126 */ 127 virtual ~BaseSetAssoc(); 128 129 /** 130 * Return the block size. 131 * @return the block size. 132 */ 133 unsigned 134 getBlockSize() const 135 { 136 return blkSize; 137 } 138 139 /** 140 * Return the subblock size. In the case of BaseSetAssoc it is always 141 * the block size. 142 * @return The block size. 143 */ 144 unsigned 145 getSubBlockSize() const 146 { 147 return blkSize; 148 } 149 150 /** 151 * Return the number of sets this cache has 152 * @return The number of sets. 153 */ 154 unsigned 155 getNumSets() const override 156 { 157 return numSets; 158 } 159 160 /** 161 * Return the number of ways this cache has 162 * @return The number of ways. 163 */ 164 unsigned 165 getNumWays() const override 166 { 167 return assoc; 168 } 169 170 /** 171 * Find the cache block given set and way 172 * @param set The set of the block. 173 * @param way The way of the block. 174 * @return The cache block. 175 */ 176 CacheBlk *findBlockBySetAndWay(int set, int way) const override; 177 178 /** 179 * Invalidate the given block. 180 * @param blk The block to invalidate. 181 */ 182 void invalidate(CacheBlk *blk) override 183 { 184 assert(blk); 185 assert(blk->isValid()); 186 tagsInUse--; 187 assert(blk->srcMasterId < cache->system->maxMasters()); 188 occupancies[blk->srcMasterId]--; 189 blk->srcMasterId = Request::invldMasterId; 190 blk->task_id = ContextSwitchTaskId::Unknown; 191 blk->tickInserted = curTick(); 192 } 193 194 /** 195 * Access block and update replacement data. May not succeed, in which case 196 * nullptr is returned. This has all the implications of a cache 197 * access and should only be used as such. Returns the access latency as a 198 * side effect. 199 * @param addr The address to find. 200 * @param is_secure True if the target memory space is secure. 201 * @param asid The address space ID. 202 * @param lat The access latency. 203 * @return Pointer to the cache block if found. 204 */ 205 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat, 206 int context_src) override 207 { 208 Addr tag = extractTag(addr); 209 int set = extractSet(addr); 210 BlkType *blk = sets[set].findBlk(tag, is_secure); 211 212 // Access all tags in parallel, hence one in each way. The data side 213 // either accesses all blocks in parallel, or one block sequentially on 214 // a hit. Sequential access with a miss doesn't access data. 215 tagAccesses += allocAssoc; 216 if (sequentialAccess) { 217 if (blk != nullptr) { 218 dataAccesses += 1; 219 } 220 } else { 221 dataAccesses += allocAssoc; 222 } 223 224 if (blk != nullptr) { 225 // If a cache hit 226 lat = accessLatency; 227 // Check if the block to be accessed is available. If not, 228 // apply the accessLatency on top of block->whenReady. 229 if (blk->whenReady > curTick() && 230 cache->ticksToCycles(blk->whenReady - curTick()) > 231 accessLatency) { 232 lat = cache->ticksToCycles(blk->whenReady - curTick()) + 233 accessLatency; 234 } 235 blk->refCount += 1; 236 } else { 237 // If a cache miss 238 lat = lookupLatency; 239 } 240 241 return blk; 242 } 243 244 /** 245 * Finds the given address in the cache, do not update replacement data. 246 * i.e. This is a no-side-effect find of a block. 247 * @param addr The address to find. 248 * @param is_secure True if the target memory space is secure. 249 * @param asid The address space ID. 250 * @return Pointer to the cache block if found. 251 */ 252 CacheBlk* findBlock(Addr addr, bool is_secure) const override; 253 254 /** 255 * Find an invalid block to evict for the address provided. 256 * If there are no invalid blocks, this will return the block 257 * in the least-recently-used position. 258 * @param addr The addr to a find a replacement candidate for. 259 * @return The candidate block. 260 */ 261 CacheBlk* findVictim(Addr addr) override 262 { 263 BlkType *blk = nullptr; 264 int set = extractSet(addr); 265 266 // prefer to evict an invalid block 267 for (int i = 0; i < allocAssoc; ++i) { 268 blk = sets[set].blks[i]; 269 if (!blk->isValid()) 270 break; 271 } 272 273 return blk; 274 } 275 276 /** 277 * Insert the new block into the cache. 278 * @param pkt Packet holding the address to update 279 * @param blk The block to update. 280 */ 281 void insertBlock(PacketPtr pkt, CacheBlk *blk) override 282 { 283 Addr addr = pkt->getAddr(); 284 MasterID master_id = pkt->req->masterId(); 285 uint32_t task_id = pkt->req->taskId(); 286 287 if (!blk->isTouched) { 288 tagsInUse++; 289 blk->isTouched = true; 290 if (!warmedUp && tagsInUse.value() >= warmupBound) { 291 warmedUp = true; 292 warmupCycle = curTick(); 293 } 294 } 295 296 // If we're replacing a block that was previously valid update 297 // stats for it. This can't be done in findBlock() because a 298 // found block might not actually be replaced there if the 299 // coherence protocol says it can't be. 300 if (blk->isValid()) { 301 replacements[0]++; 302 totalRefs += blk->refCount; 303 ++sampledRefs; 304 blk->refCount = 0; 305 306 // deal with evicted block 307 assert(blk->srcMasterId < cache->system->maxMasters()); 308 occupancies[blk->srcMasterId]--; 309 310 blk->invalidate(); 311 } 312 313 blk->isTouched = true; 314 315 // Set tag for new block. Caller is responsible for setting status. 316 blk->tag = extractTag(addr); 317 318 // deal with what we are bringing in 319 assert(master_id < cache->system->maxMasters()); 320 occupancies[master_id]++; 321 blk->srcMasterId = master_id; 322 blk->task_id = task_id; 323 blk->tickInserted = curTick(); 324 325 // We only need to write into one tag and one data block. 326 tagAccesses += 1; 327 dataAccesses += 1; 328 } 329 330 /** 331 * Limit the allocation for the cache ways. 332 * @param ways The maximum number of ways available for replacement. 333 */ 334 virtual void setWayAllocationMax(int ways) override 335 { 336 fatal_if(ways < 1, "Allocation limit must be greater than zero"); 337 allocAssoc = ways; 338 } 339 340 /** 341 * Get the way allocation mask limit. 342 * @return The maximum number of ways available for replacement. 343 */ 344 virtual int getWayAllocationMax() const override 345 { 346 return allocAssoc; 347 } 348 349 /** 350 * Generate the tag from the given address. 351 * @param addr The address to get the tag from. 352 * @return The tag of the address. 353 */ 354 Addr extractTag(Addr addr) const override 355 { 356 return (addr >> tagShift); 357 } 358 359 /** 360 * Calculate the set index from the address. 361 * @param addr The address to get the set from. 362 * @return The set index of the address. 363 */ 364 int extractSet(Addr addr) const override 365 { 366 return ((addr >> setShift) & setMask); 367 } 368 369 /** 370 * Align an address to the block size. 371 * @param addr the address to align. 372 * @return The block address. 373 */ 374 Addr blkAlign(Addr addr) const 375 { 376 return (addr & ~(Addr)blkMask); 377 } 378 379 /** 380 * Regenerate the block address from the tag. 381 * @param tag The tag of the block. 382 * @param set The set of the block. 383 * @return The block address. 384 */ 385 Addr regenerateBlkAddr(Addr tag, unsigned set) const override 386 { 387 return ((tag << tagShift) | ((Addr)set << setShift)); 388 } 389 390 /** 391 * Called at end of simulation to complete average block reference stats. 392 */ 393 void cleanupRefs() override; 394 395 /** 396 * Print all tags used 397 */ 398 std::string print() const override; 399 400 /** 401 * Called prior to dumping stats to compute task occupancy 402 */ 403 void computeStats() override; 404 405 /** 406 * Visit each block in the tag store and apply a visitor to the 407 * block. 408 * 409 * The visitor should be a function (or object that behaves like a 410 * function) that takes a cache block reference as its parameter 411 * and returns a bool. A visitor can request the traversal to be 412 * stopped by returning false, returning true causes it to be 413 * called for the next block in the tag store. 414 * 415 * \param visitor Visitor to call on each block. 416 */ 417 void forEachBlk(CacheBlkVisitor &visitor) override { 418 for (unsigned i = 0; i < numSets * assoc; ++i) { 419 if (!visitor(blks[i])) 420 return; 421 } 422 } 423}; 424 425#endif // __MEM_CACHE_TAGS_BASESETASSOC_HH__ 426