src/mem/cache/tags/sector_tags.cc

   1 /*
   2  * Copyright (c) 2018 Inria
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  *
  28  * Authors: Daniel Carvalho
  29  */
  30
  31 /**
  32  * @file
  33  * Definitions of a sector tag store.
  34  */
  35
  36 #include "mem/cache/tags/sector_tags.hh"
  37
  38 #include <cassert>
  39 #include <memory>
  40 #include <string>
  41
  42 #include "base/intmath.hh"
  43 #include "base/logging.hh"
  44 #include "base/types.hh"
  45 #include "mem/cache/base.hh"
  46 #include "mem/cache/replacement_policies/base.hh"
  47 #include "mem/cache/replacement_policies/replaceable_entry.hh"
  48 #include "mem/cache/tags/indexing_policies/base.hh"
  49
  50 SectorTags::SectorTags(const SectorTagsParams *p)
  51     : BaseTags(p), allocAssoc(p->assoc),
  52       sequentialAccess(p->sequential_access),
  53       replacementPolicy(p->replacement_policy),
  54       numBlocksPerSector(p->num_blocks_per_sector),
  55       numSectors(numBlocks / p->num_blocks_per_sector), blks(numBlocks),
  56       secBlks(numSectors), sectorShift(floorLog2(blkSize)),
  57       sectorMask(numBlocksPerSector - 1)
  58 {
  59     // Check parameters
  60     fatal_if(blkSize < 4 || !isPowerOf2(blkSize),
  61              "Block size must be at least 4 and a power of 2");
  62     fatal_if(!isPowerOf2(numBlocksPerSector),
  63              "# of blocks per sector must be non-zero and a power of 2");
  64 }
  65
  66 void
  67 SectorTags::tagsInit()
  68 {
  69     // Initialize all blocks
  70     unsigned blk_index = 0;       // index into blks array
  71     for (unsigned sec_blk_index = 0; sec_blk_index < numSectors;
  72          sec_blk_index++)
  73     {
  74         // Locate next cache sector
  75         SectorBlk* sec_blk = &secBlks[sec_blk_index];
  76
  77         // Link block to indexing policy
  78         indexingPolicy->setEntry(sec_blk, sec_blk_index);
  79
  80         // Associate a replacement data entry to the sector
  81         sec_blk->replacementData = replacementPolicy->instantiateEntry();
  82
  83         // Initialize all blocks in this sector
  84         sec_blk->blks.resize(numBlocksPerSector);
  85         for (unsigned k = 0; k < numBlocksPerSector; ++k){
  86             // Select block within the set to be linked
  87             SectorSubBlk*& blk = sec_blk->blks[k];
  88
  89             // Locate next cache block
  90             blk = &blks[blk_index];
  91
  92             // Associate a data chunk to the block
  93             blk->data = &dataBlks[blkSize*blk_index];
  94
  95             // Associate sector block to this block
  96             blk->setSectorBlock(sec_blk);
  97
  98             // Associate the sector replacement data to this block
  99             blk->replacementData = sec_blk->replacementData;
 100
 101             // Set its index and sector offset
 102             blk->setSectorOffset(k);
 103
 104             // Update block index
 105             ++blk_index;
 106         }
 107     }
 108 }
 109
 110 void
 111 SectorTags::invalidate(CacheBlk *blk)
 112 {
 113     BaseTags::invalidate(blk);
 114
 115     // Get block's sector
 116     SectorSubBlk* sub_blk = static_cast<SectorSubBlk*>(blk);
 117     const SectorBlk* sector_blk = sub_blk->getSectorBlock();
 118
 119     // When a block in a sector is invalidated, it does not make the tag
 120     // invalid automatically, as there might be other blocks in the sector
 121     // using it. The tag is invalidated only when there is a single block
 122     // in the sector.
 123     if (!sector_blk->isValid()) {
 124         // Decrease the number of tags in use
 125         tagsInUse--;
 126
 127         // Invalidate replacement data, as we're invalidating the sector
 128         replacementPolicy->invalidate(sector_blk->replacementData);
 129     }
 130 }
 131
 132 CacheBlk*
 133 SectorTags::accessBlock(Addr addr, bool is_secure, Cycles &lat)
 134 {
 135     CacheBlk *blk = findBlock(addr, is_secure);
 136
 137     // Access all tags in parallel, hence one in each way.  The data side
 138     // either accesses all blocks in parallel, or one block sequentially on
 139     // a hit.  Sequential access with a miss doesn't access data.
 140     tagAccesses += allocAssoc;
 141     if (sequentialAccess) {
 142         if (blk != nullptr) {
 143             dataAccesses += 1;
 144         }
 145     } else {
 146         dataAccesses += allocAssoc*numBlocksPerSector;
 147     }
 148
 149     // If a cache hit
 150     if (blk != nullptr) {
 151         // Update number of references to accessed block
 152         blk->refCount++;
 153
 154         // Get block's sector
 155         SectorSubBlk* sub_blk = static_cast<SectorSubBlk*>(blk);
 156         const SectorBlk* sector_blk = sub_blk->getSectorBlock();
 157
 158         // Update replacement data of accessed block, which is shared with
 159         // the whole sector it belongs to
 160         replacementPolicy->touch(sector_blk->replacementData);
 161     }
 162
 163     // The tag lookup latency is the same for a hit or a miss
 164     lat = lookupLatency;
 165
 166     return blk;
 167 }
 168
 169 void
 170 SectorTags::insertBlock(const Addr addr, const bool is_secure,
 171                         const int src_master_ID, const uint32_t task_ID,
 172                         CacheBlk *blk)
 173 {
 174     // Get block's sector
 175     SectorSubBlk* sub_blk = static_cast<SectorSubBlk*>(blk);
 176     const SectorBlk* sector_blk = sub_blk->getSectorBlock();
 177
 178     // When a block is inserted, the tag is only a newly used tag if the
 179     // sector was not previously present in the cache.
 180     if (sector_blk->isValid()) {
 181         // An existing entry's replacement data is just updated
 182         replacementPolicy->touch(sector_blk->replacementData);
 183     } else {
 184         // Increment tag counter
 185         tagsInUse++;
 186
 187         // A new entry resets the replacement data
 188         replacementPolicy->reset(sector_blk->replacementData);
 189     }
 190
 191     // Do common block insertion functionality
 192     BaseTags::insertBlock(addr, is_secure, src_master_ID, task_ID, blk);
 193 }
 194
 195 CacheBlk*
 196 SectorTags::findBlock(Addr addr, bool is_secure) const
 197 {
 198     // Extract sector tag
 199     const Addr tag = extractTag(addr);
 200
 201     // The address can only be mapped to a specific location of a sector
 202     // due to sectors being composed of contiguous-address entries
 203     const Addr offset = extractSectorOffset(addr);
 204
 205     // Find all possible sector entries that may contain the given address
 206     const std::vector<ReplaceableEntry*> entries =
 207         indexingPolicy->getPossibleEntries(addr);
 208
 209     // Search for block
 210     for (const auto& sector : entries) {
 211         auto blk = static_cast<SectorBlk*>(sector)->blks[offset];
 212         if (blk->getTag() == tag && blk->isValid() &&
 213             blk->isSecure() == is_secure) {
 214             return blk;
 215         }
 216     }
 217
 218     // Did not find block
 219     return nullptr;
 220 }
 221
 222 CacheBlk*
 223 SectorTags::findVictim(Addr addr, const bool is_secure,
 224                        std::vector<CacheBlk*>& evict_blks) const
 225 {
 226     // Get possible entries to be victimized
 227     const std::vector<ReplaceableEntry*> sector_entries =
 228         indexingPolicy->getPossibleEntries(addr);
 229
 230     // Check if the sector this address belongs to has been allocated
 231     Addr tag = extractTag(addr);
 232     SectorBlk* victim_sector = nullptr;
 233     for (const auto& sector : sector_entries) {
 234         SectorBlk* sector_blk = static_cast<SectorBlk*>(sector);
 235         if ((tag == sector_blk->getTag()) && sector_blk->isValid() &&
 236             (is_secure == sector_blk->isSecure())){
 237             victim_sector = sector_blk;
 238             break;
 239         }
 240     }
 241
 242     // If the sector is not present
 243     if (victim_sector == nullptr){
 244         // Choose replacement victim from replacement candidates
 245         victim_sector = static_cast<SectorBlk*>(replacementPolicy->getVictim(
 246                                                 sector_entries));
 247     }
 248
 249     // Get the entry of the victim block within the sector
 250     SectorSubBlk* victim = victim_sector->blks[extractSectorOffset(addr)];
 251
 252     // Get evicted blocks. Blocks are only evicted if the sectors mismatch and
 253     // the currently existing sector is valid.
 254     if ((tag == victim_sector->getTag()) &&
 255         (is_secure == victim_sector->isSecure())){
 256         // It would be a hit if victim was valid, and upgrades do not call
 257         // findVictim, so it cannot happen
 258         assert(!victim->isValid());
 259     } else {
 260         // The whole sector must be evicted to make room for the new sector
 261         for (const auto& blk : victim_sector->blks){
 262             evict_blks.push_back(blk);
 263         }
 264     }
 265
 266     return victim;
 267 }
 268
 269 int
 270 SectorTags::extractSectorOffset(Addr addr) const
 271 {
 272     return (addr >> sectorShift) & sectorMask;
 273 }
 274
 275 Addr
 276 SectorTags::regenerateBlkAddr(const CacheBlk* blk) const
 277 {
 278     const SectorSubBlk* blk_cast = static_cast<const SectorSubBlk*>(blk);
 279     const SectorBlk* sec_blk = blk_cast->getSectorBlock();
 280     const Addr sec_addr = indexingPolicy->regenerateAddr(blk->tag, sec_blk);
 281     return sec_addr | ((Addr)blk_cast->getSectorOffset() << sectorShift);
 282 }
 283
 284 void
 285 SectorTags::forEachBlk(std::function<void(CacheBlk &)> visitor)
 286 {
 287     for (SectorSubBlk& blk : blks) {
 288         visitor(blk);
 289     }
 290 }
 291
 292 bool
 293 SectorTags::anyBlk(std::function<bool(CacheBlk &)> visitor)
 294 {
 295     for (SectorSubBlk& blk : blks) {
 296         if (visitor(blk)) {
 297             return true;
 298         }
 299     }
 300     return false;
 301 }
 302
 303 SectorTags *
 304 SectorTagsParams::create()
 305 {
 306     // There must be a indexing policy
 307     fatal_if(!indexing_policy, "An indexing policy is required");
 308
 309     return new SectorTags(this);
 310 }