base_set_assoc.hh revision 12753:fe5b2dbe42bb
1/* 2 * Copyright (c) 2012-2014,2017 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 <functional> 52#include <string> 53#include <vector> 54 55#include "base/logging.hh" 56#include "base/types.hh" 57#include "debug/CacheRepl.hh" 58#include "mem/cache/base.hh" 59#include "mem/cache/blk.hh" 60#include "mem/cache/replacement_policies/base.hh" 61#include "mem/cache/tags/base.hh" 62#include "mem/cache/tags/cacheset.hh" 63#include "mem/packet.hh" 64#include "params/BaseSetAssoc.hh" 65 66/** 67 * A BaseSetAssoc cache tag store. 68 * @sa \ref gem5MemorySystem "gem5 Memory System" 69 * 70 * The BaseSetAssoc placement policy divides the cache into s sets of w 71 * cache lines (ways). A cache line is mapped onto a set, and can be placed 72 * into any of the ways of this set. 73 */ 74class BaseSetAssoc : public BaseTags 75{ 76 public: 77 /** Typedef the block type used in this tag store. */ 78 typedef CacheBlk BlkType; 79 /** Typedef the set type used in this tag store. */ 80 typedef CacheSet<CacheBlk> SetType; 81 82 protected: 83 /** The associativity of the cache. */ 84 const unsigned assoc; 85 /** The allocatable associativity of the cache (alloc mask). */ 86 unsigned allocAssoc; 87 88 /** The cache blocks. */ 89 std::vector<BlkType> blks; 90 91 /** The number of sets in the cache. */ 92 const unsigned numSets; 93 94 /** Whether tags and data are accessed sequentially. */ 95 const bool sequentialAccess; 96 97 /** The cache sets. */ 98 std::vector<SetType> sets; 99 100 /** The amount to shift the address to get the set. */ 101 int setShift; 102 /** The amount to shift the address to get the tag. */ 103 int tagShift; 104 /** Mask out all bits that aren't part of the set index. */ 105 unsigned setMask; 106 107 /** Replacement policy */ 108 BaseReplacementPolicy *replacementPolicy; 109 110 public: 111 /** Convenience typedef. */ 112 typedef BaseSetAssocParams Params; 113 114 /** 115 * Construct and initialize this tag store. 116 */ 117 BaseSetAssoc(const Params *p); 118 119 /** 120 * Destructor 121 */ 122 virtual ~BaseSetAssoc() {}; 123 124 /** 125 * This function updates the tags when a block is invalidated. It also 126 * updates the replacement data. 127 * 128 * @param blk The block to invalidate. 129 */ 130 void invalidate(CacheBlk *blk) override; 131 132 /** 133 * Access block and update replacement data. May not succeed, in which case 134 * nullptr is returned. This has all the implications of a cache 135 * access and should only be used as such. Returns the access latency as a 136 * side effect. 137 * @param addr The address to find. 138 * @param is_secure True if the target memory space is secure. 139 * @param lat The access latency. 140 * @return Pointer to the cache block if found. 141 */ 142 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override 143 { 144 BlkType *blk = findBlock(addr, is_secure); 145 146 // Access all tags in parallel, hence one in each way. The data side 147 // either accesses all blocks in parallel, or one block sequentially on 148 // a hit. Sequential access with a miss doesn't access data. 149 tagAccesses += allocAssoc; 150 if (sequentialAccess) { 151 if (blk != nullptr) { 152 dataAccesses += 1; 153 } 154 } else { 155 dataAccesses += allocAssoc; 156 } 157 158 if (blk != nullptr) { 159 // If a cache hit 160 lat = accessLatency; 161 // Check if the block to be accessed is available. If not, 162 // apply the accessLatency on top of block->whenReady. 163 if (blk->whenReady > curTick() && 164 cache->ticksToCycles(blk->whenReady - curTick()) > 165 accessLatency) { 166 lat = cache->ticksToCycles(blk->whenReady - curTick()) + 167 accessLatency; 168 } 169 170 // Update number of references to accessed block 171 blk->refCount++; 172 173 // Update replacement data of accessed block 174 replacementPolicy->touch(blk->replacementData); 175 } else { 176 // If a cache miss 177 lat = lookupLatency; 178 } 179 180 return blk; 181 } 182 183 /** 184 * Finds the given address in the cache, do not update replacement data. 185 * i.e. This is a no-side-effect find of a block. 186 * @param addr The address to find. 187 * @param is_secure True if the target memory space is secure. 188 * @param asid The address space ID. 189 * @return Pointer to the cache block if found. 190 */ 191 CacheBlk* findBlock(Addr addr, bool is_secure) const override; 192 193 /** 194 * Find a block given set and way. 195 * 196 * @param set The set of the block. 197 * @param way The way of the block. 198 * @return The block. 199 */ 200 ReplaceableEntry* findBlockBySetAndWay(int set, int way) const override; 201 202 /** 203 * Find replacement victim based on address. The list of evicted blocks 204 * only contains the victim. 205 * 206 * @param addr Address to find a victim for. 207 * @param is_secure True if the target memory space is secure. 208 * @param evict_blks Cache blocks to be evicted. 209 * @return Cache block to be replaced. 210 */ 211 CacheBlk* findVictim(Addr addr, const bool is_secure, 212 std::vector<CacheBlk*>& evict_blks) const override 213 { 214 // Get possible locations for the victim block 215 std::vector<CacheBlk*> locations = getPossibleLocations(addr); 216 217 // Choose replacement victim from replacement candidates 218 CacheBlk* victim = static_cast<CacheBlk*>(replacementPolicy->getVictim( 219 std::vector<ReplaceableEntry*>( 220 locations.begin(), locations.end()))); 221 222 // There is only one eviction for this replacement 223 evict_blks.push_back(victim); 224 225 DPRINTF(CacheRepl, "set %x, way %x: selecting blk for replacement\n", 226 victim->set, victim->way); 227 228 return victim; 229 } 230 231 /** 232 * Find all possible block locations for insertion and replacement of 233 * an address. Should be called immediately before ReplacementPolicy's 234 * findVictim() not to break cache resizing. 235 * Returns blocks in all ways belonging to the set of the address. 236 * 237 * @param addr The addr to a find possible locations for. 238 * @return The possible locations. 239 */ 240 const std::vector<CacheBlk*> getPossibleLocations(Addr addr) const 241 { 242 return sets[extractSet(addr)].blks; 243 } 244 245 /** 246 * Insert the new block into the cache and update replacement data. 247 * 248 * @param pkt Packet holding the address to update 249 * @param blk The block to update. 250 */ 251 void insertBlock(const PacketPtr pkt, CacheBlk *blk) override 252 { 253 // Insert block 254 BaseTags::insertBlock(pkt, blk); 255 256 // Increment tag counter 257 tagsInUse++; 258 259 // Update replacement policy 260 replacementPolicy->reset(blk->replacementData); 261 } 262 263 /** 264 * Limit the allocation for the cache ways. 265 * @param ways The maximum number of ways available for replacement. 266 */ 267 virtual void setWayAllocationMax(int ways) override 268 { 269 fatal_if(ways < 1, "Allocation limit must be greater than zero"); 270 allocAssoc = ways; 271 } 272 273 /** 274 * Get the way allocation mask limit. 275 * @return The maximum number of ways available for replacement. 276 */ 277 virtual int getWayAllocationMax() const override 278 { 279 return allocAssoc; 280 } 281 282 /** 283 * Generate the tag from the given address. 284 * @param addr The address to get the tag from. 285 * @return The tag of the address. 286 */ 287 Addr extractTag(Addr addr) const override 288 { 289 return (addr >> tagShift); 290 } 291 292 /** 293 * Regenerate the block address from the tag and set. 294 * 295 * @param block The block. 296 * @return the block address. 297 */ 298 Addr regenerateBlkAddr(const CacheBlk* blk) const override 299 { 300 return ((blk->tag << tagShift) | ((Addr)blk->set << setShift)); 301 } 302 303 void forEachBlk(std::function<void(CacheBlk &)> visitor) override { 304 for (CacheBlk& blk : blks) { 305 visitor(blk); 306 } 307 } 308 309 bool anyBlk(std::function<bool(CacheBlk &)> visitor) override { 310 for (CacheBlk& blk : blks) { 311 if (visitor(blk)) { 312 return true; 313 } 314 } 315 return false; 316 } 317 318 private: 319 /** 320 * Calculate the set index from the address. 321 * 322 * @param addr The address to get the set from. 323 * @return The set index of the address. 324 */ 325 int extractSet(Addr addr) const 326 { 327 return ((addr >> setShift) & setMask); 328 } 329}; 330 331#endif //__MEM_CACHE_TAGS_BASE_SET_ASSOC_HH__ 332