base_set_assoc.hh revision 12548:285f1792a2da
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_BASE_SET_ASSOC_HH__ 49#define __MEM_CACHE_TAGS_BASE_SET_ASSOC_HH__ 50 51#include <cassert> 52#include <cstring> 53#include <memory> 54#include <vector> 55 56#include "mem/cache/base.hh" 57#include "mem/cache/blk.hh" 58#include "mem/cache/tags/base.hh" 59#include "mem/cache/tags/cacheset.hh" 60#include "mem/packet.hh" 61#include "params/BaseSetAssoc.hh" 62 63/** 64 * A BaseSetAssoc cache tag store. 65 * @sa \ref gem5MemorySystem "gem5 Memory System" 66 * 67 * The BaseSetAssoc tags provide a base, as well as the functionality 68 * common to any set associative tags. Any derived class must implement 69 * the methods related to the specifics of the actual replacment policy. 70 * These are: 71 * 72 * BlkType* accessBlock(); 73 * BlkType* findVictim(); 74 * void insertBlock(); 75 * void invalidate(); 76 */ 77class BaseSetAssoc : public BaseTags 78{ 79 public: 80 /** Typedef the block type used in this tag store. */ 81 typedef CacheBlk BlkType; 82 /** Typedef the set type used in this tag store. */ 83 typedef CacheSet<CacheBlk> SetType; 84 85 86 protected: 87 /** The associativity of the cache. */ 88 const unsigned assoc; 89 /** The allocatable associativity of the cache (alloc mask). */ 90 unsigned allocAssoc; 91 92 /** The cache blocks. */ 93 std::vector<BlkType> blks; 94 /** The data blocks, 1 per cache block. */ 95 std::unique_ptr<uint8_t[]> dataBlks; 96 97 /** The number of sets in the cache. */ 98 const unsigned numSets; 99 100 /** Whether tags and data are accessed sequentially. */ 101 const bool sequentialAccess; 102 103 /** The cache sets. */ 104 std::vector<SetType> sets; 105 106 /** The amount to shift the address to get the set. */ 107 int setShift; 108 /** The amount to shift the address to get the tag. */ 109 int tagShift; 110 /** Mask out all bits that aren't part of the set index. */ 111 unsigned setMask; 112 113public: 114 115 /** Convenience typedef. */ 116 typedef BaseSetAssocParams Params; 117 118 /** 119 * Construct and initialize this tag store. 120 */ 121 BaseSetAssoc(const Params *p); 122 123 /** 124 * Destructor 125 */ 126 virtual ~BaseSetAssoc() {}; 127 128 /** 129 * Find the cache block given set and way 130 * @param set The set of the block. 131 * @param way The way of the block. 132 * @return The cache block. 133 */ 134 CacheBlk *findBlockBySetAndWay(int set, int way) const override; 135 136 /** 137 * Invalidate the given block. 138 * @param blk The block to invalidate. 139 */ 140 void invalidate(CacheBlk *blk) override 141 { 142 assert(blk); 143 assert(blk->isValid()); 144 tagsInUse--; 145 assert(blk->srcMasterId < cache->system->maxMasters()); 146 occupancies[blk->srcMasterId]--; 147 blk->srcMasterId = Request::invldMasterId; 148 blk->task_id = ContextSwitchTaskId::Unknown; 149 blk->tickInserted = curTick(); 150 } 151 152 /** 153 * Access block and update replacement data. May not succeed, in which case 154 * nullptr is returned. This has all the implications of a cache 155 * access and should only be used as such. Returns the access latency as a 156 * side effect. 157 * @param addr The address to find. 158 * @param is_secure True if the target memory space is secure. 159 * @param lat The access latency. 160 * @return Pointer to the cache block if found. 161 */ 162 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override 163 { 164 Addr tag = extractTag(addr); 165 int set = extractSet(addr); 166 BlkType *blk = sets[set].findBlk(tag, is_secure); 167 168 // Access all tags in parallel, hence one in each way. The data side 169 // either accesses all blocks in parallel, or one block sequentially on 170 // a hit. Sequential access with a miss doesn't access data. 171 tagAccesses += allocAssoc; 172 if (sequentialAccess) { 173 if (blk != nullptr) { 174 dataAccesses += 1; 175 } 176 } else { 177 dataAccesses += allocAssoc; 178 } 179 180 if (blk != nullptr) { 181 // If a cache hit 182 lat = accessLatency; 183 // Check if the block to be accessed is available. If not, 184 // apply the accessLatency on top of block->whenReady. 185 if (blk->whenReady > curTick() && 186 cache->ticksToCycles(blk->whenReady - curTick()) > 187 accessLatency) { 188 lat = cache->ticksToCycles(blk->whenReady - curTick()) + 189 accessLatency; 190 } 191 blk->refCount += 1; 192 } else { 193 // If a cache miss 194 lat = lookupLatency; 195 } 196 197 return blk; 198 } 199 200 /** 201 * Finds the given address in the cache, do not update replacement data. 202 * i.e. This is a no-side-effect find of a block. 203 * @param addr The address to find. 204 * @param is_secure True if the target memory space is secure. 205 * @param asid The address space ID. 206 * @return Pointer to the cache block if found. 207 */ 208 CacheBlk* findBlock(Addr addr, bool is_secure) const override; 209 210 /** 211 * Find an invalid block to evict for the address provided. 212 * If there are no invalid blocks, this will return the block 213 * in the least-recently-used position. 214 * @param addr The addr to a find a replacement candidate for. 215 * @return The candidate block. 216 */ 217 CacheBlk* findVictim(Addr addr) override 218 { 219 BlkType *blk = nullptr; 220 int set = extractSet(addr); 221 222 // prefer to evict an invalid block 223 for (int i = 0; i < allocAssoc; ++i) { 224 blk = sets[set].blks[i]; 225 if (!blk->isValid()) 226 break; 227 } 228 229 return blk; 230 } 231 232 /** 233 * Insert the new block into the cache. 234 * @param pkt Packet holding the address to update 235 * @param blk The block to update. 236 */ 237 void insertBlock(PacketPtr pkt, CacheBlk *blk) override 238 { 239 Addr addr = pkt->getAddr(); 240 MasterID master_id = pkt->req->masterId(); 241 uint32_t task_id = pkt->req->taskId(); 242 243 if (!blk->isTouched) { 244 tagsInUse++; 245 blk->isTouched = true; 246 if (!warmedUp && tagsInUse.value() >= warmupBound) { 247 warmedUp = true; 248 warmupCycle = curTick(); 249 } 250 } 251 252 // If we're replacing a block that was previously valid update 253 // stats for it. This can't be done in findBlock() because a 254 // found block might not actually be replaced there if the 255 // coherence protocol says it can't be. 256 if (blk->isValid()) { 257 replacements[0]++; 258 totalRefs += blk->refCount; 259 ++sampledRefs; 260 blk->refCount = 0; 261 262 // deal with evicted block 263 assert(blk->srcMasterId < cache->system->maxMasters()); 264 occupancies[blk->srcMasterId]--; 265 266 blk->invalidate(); 267 } 268 269 blk->isTouched = true; 270 271 // Set tag for new block. Caller is responsible for setting status. 272 blk->tag = extractTag(addr); 273 274 // deal with what we are bringing in 275 assert(master_id < cache->system->maxMasters()); 276 occupancies[master_id]++; 277 blk->srcMasterId = master_id; 278 blk->task_id = task_id; 279 blk->tickInserted = curTick(); 280 281 // We only need to write into one tag and one data block. 282 tagAccesses += 1; 283 dataAccesses += 1; 284 } 285 286 /** 287 * Limit the allocation for the cache ways. 288 * @param ways The maximum number of ways available for replacement. 289 */ 290 virtual void setWayAllocationMax(int ways) override 291 { 292 fatal_if(ways < 1, "Allocation limit must be greater than zero"); 293 allocAssoc = ways; 294 } 295 296 /** 297 * Get the way allocation mask limit. 298 * @return The maximum number of ways available for replacement. 299 */ 300 virtual int getWayAllocationMax() const override 301 { 302 return allocAssoc; 303 } 304 305 /** 306 * Generate the tag from the given address. 307 * @param addr The address to get the tag from. 308 * @return The tag of the address. 309 */ 310 Addr extractTag(Addr addr) const override 311 { 312 return (addr >> tagShift); 313 } 314 315 /** 316 * Calculate the set index from the address. 317 * @param addr The address to get the set from. 318 * @return The set index of the address. 319 */ 320 int extractSet(Addr addr) const override 321 { 322 return ((addr >> setShift) & setMask); 323 } 324 325 /** 326 * Regenerate the block address from the tag. 327 * @param tag The tag of the block. 328 * @param set The set of the block. 329 * @return The block address. 330 */ 331 Addr regenerateBlkAddr(Addr tag, unsigned set) const override 332 { 333 return ((tag << tagShift) | ((Addr)set << setShift)); 334 } 335 336 /** 337 * Called at end of simulation to complete average block reference stats. 338 */ 339 void cleanupRefs() override; 340 341 /** 342 * Print all tags used 343 */ 344 std::string print() const override; 345 346 /** 347 * Called prior to dumping stats to compute task occupancy 348 */ 349 void computeStats() override; 350 351 /** 352 * Visit each block in the tag store and apply a visitor to the 353 * block. 354 * 355 * The visitor should be a function (or object that behaves like a 356 * function) that takes a cache block reference as its parameter 357 * and returns a bool. A visitor can request the traversal to be 358 * stopped by returning false, returning true causes it to be 359 * called for the next block in the tag store. 360 * 361 * \param visitor Visitor to call on each block. 362 */ 363 void forEachBlk(CacheBlkVisitor &visitor) override { 364 for (unsigned i = 0; i < numSets * assoc; ++i) { 365 if (!visitor(blks[i])) 366 return; 367 } 368 } 369}; 370 371#endif //__MEM_CACHE_TAGS_BASE_SET_ASSOC_HH__ 372