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author | Daniel R. Carvalho <odanrc@yahoo.com.br> | 2018-04-05 11:54:39 +0200 |
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committer | Daniel Carvalho <odanrc@yahoo.com.br> | 2018-06-13 07:58:00 +0000 |
commit | 5bb8643808e81412ef634c142a9a403032d9141f (patch) | |
tree | 5ffb310c35ca4e154621654046672981a2fb0342 /src/mem/cache/tags/sector_tags.cc | |
parent | 8008ce25e9ff7e82e4bd0b7da041a31dc841057b (diff) | |
download | gem5-5bb8643808e81412ef634c142a9a403032d9141f.tar.xz |
mem-cache: Create Sector Cache
Implementation of Sector Caches, i.e., a cache with multiple
sequential data entries per tag entry for Set Associtive
placement policies.
Change-Id: I8e1e9448fa44ba308ccb16cd5bcc5fd36c988feb
Reviewed-on: https://gem5-review.googlesource.com/9741
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Diffstat (limited to 'src/mem/cache/tags/sector_tags.cc')
-rw-r--r-- | src/mem/cache/tags/sector_tags.cc | 354 |
1 files changed, 354 insertions, 0 deletions
diff --git a/src/mem/cache/tags/sector_tags.cc b/src/mem/cache/tags/sector_tags.cc new file mode 100644 index 000000000..27e89829d --- /dev/null +++ b/src/mem/cache/tags/sector_tags.cc @@ -0,0 +1,354 @@ +/* + * Copyright (c) 2018 Inria + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer; + * redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution; + * neither the name of the copyright holders nor the names of its + * contributors may be used to endorse or promote products derived from + * this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + * Authors: Daniel Carvalho + */ + +/** + * @file + * Definitions of a base set associative sector tag store. + */ + +#include "mem/cache/tags/sector_tags.hh" + +#include <cassert> +#include <memory> +#include <string> + +#include "base/intmath.hh" +#include "base/logging.hh" +#include "base/types.hh" +#include "debug/CacheRepl.hh" +#include "mem/cache/base.hh" +#include "mem/cache/replacement_policies/base.hh" + +SectorTags::SectorTags(const SectorTagsParams *p) + : BaseTags(p), assoc(p->assoc), allocAssoc(p->assoc), + sequentialAccess(p->sequential_access), + replacementPolicy(p->replacement_policy), + numBlocksPerSector(p->num_blocks_per_sector), + numSectors(numBlocks / p->num_blocks_per_sector), + numSets(numSectors / p->assoc), + blks(numBlocks), secBlks(numSectors), sets(numSets), + sectorShift(floorLog2(blkSize)), + setShift(sectorShift + floorLog2(numBlocksPerSector)), + tagShift(setShift + floorLog2(numSets)), + sectorMask(numBlocksPerSector - 1), setMask(numSets - 1) +{ + // Check parameters + fatal_if(blkSize < 4 || !isPowerOf2(blkSize), + "Block size must be at least 4 and a power of 2"); + fatal_if(!isPowerOf2(numSets), + "# of sets must be non-zero and a power of 2"); + fatal_if(!isPowerOf2(numBlocksPerSector), + "# of blocks per sector must be non-zero and a power of 2"); + fatal_if(assoc <= 0, "associativity must be greater than zero"); + + // Initialize all sets + unsigned sec_blk_index = 0; // index into sector blks array + unsigned blk_index = 0; // index into blks array + for (unsigned i = 0; i < numSets; ++i) { + sets[i].resize(assoc); + + // Initialize all sectors in this set + for (unsigned j = 0; j < assoc; ++j) { + // Select block within the set to be linked + SectorBlk*& sec_blk = sets[i][j]; + + // Locate next cache sector + sec_blk = &secBlks[sec_blk_index]; + + // Associate a replacement data entry to the sector + sec_blk->replacementData = replacementPolicy->instantiateEntry(); + + // Initialize all blocks in this sector + sec_blk->blks.resize(numBlocksPerSector); + for (unsigned k = 0; k < numBlocksPerSector; ++k){ + // Select block within the set to be linked + SectorSubBlk*& blk = sec_blk->blks[k]; + + // Locate next cache block + blk = &blks[blk_index]; + + // Associate a data chunk to the block + blk->data = &dataBlks[blkSize*blk_index]; + + // Associate sector block to this block + blk->setSectorBlock(sec_blk); + + // Associate the sector replacement data to this block + blk->replacementData = sec_blk->replacementData; + + // Set its set, way and sector offset + blk->set = i; + blk->way = j; + blk->setSectorOffset(k); + + // Update block index + ++blk_index; + } + + // Update sector block index + ++sec_blk_index; + } + } +} + +void +SectorTags::invalidate(CacheBlk *blk) +{ + BaseTags::invalidate(blk); + + // Get block's sector + SectorSubBlk* sub_blk = static_cast<SectorSubBlk*>(blk); + const SectorBlk* sector_blk = sub_blk->getSectorBlock(); + + // When a block in a sector is invalidated, it does not make the tag + // invalid automatically, as there might be other blocks in the sector + // using it. The tag is invalidated only when there is a single block + // in the sector. + if (!sector_blk->isValid()) { + // Decrease the number of tags in use + tagsInUse--; + + // Invalidate replacement data, as we're invalidating the sector + replacementPolicy->invalidate(sector_blk->replacementData); + } +} + +CacheBlk* +SectorTags::accessBlock(Addr addr, bool is_secure, Cycles &lat) +{ + CacheBlk *blk = findBlock(addr, is_secure); + + // Access all tags in parallel, hence one in each way. The data side + // either accesses all blocks in parallel, or one block sequentially on + // a hit. Sequential access with a miss doesn't access data. + tagAccesses += allocAssoc; + if (sequentialAccess) { + if (blk != nullptr) { + dataAccesses += 1; + } + } else { + dataAccesses += allocAssoc*numBlocksPerSector; + } + + if (blk != nullptr) { + // If a cache hit + lat = accessLatency; + // Check if the block to be accessed is available. If not, + // apply the accessLatency on top of block->whenReady. + if (blk->whenReady > curTick() && + cache->ticksToCycles(blk->whenReady - curTick()) > + accessLatency) { + lat = cache->ticksToCycles(blk->whenReady - curTick()) + + accessLatency; + } + + // Update number of references to accessed block + blk->refCount++; + + // Get block's sector + SectorSubBlk* sub_blk = static_cast<SectorSubBlk*>(blk); + const SectorBlk* sector_blk = sub_blk->getSectorBlock(); + + // Update replacement data of accessed block, which is shared with + // the whole sector it belongs to + replacementPolicy->touch(sector_blk->replacementData); + } else { + // If a cache miss + lat = lookupLatency; + } + + return blk; +} + +const std::vector<SectorBlk*> +SectorTags::getPossibleLocations(Addr addr) const +{ + return sets[extractSet(addr)]; +} + +void +SectorTags::insertBlock(PacketPtr pkt, CacheBlk *blk) +{ + // Insert block + BaseTags::insertBlock(pkt, blk); + + // Get block's sector + SectorSubBlk* sub_blk = static_cast<SectorSubBlk*>(blk); + const SectorBlk* sector_blk = sub_blk->getSectorBlock(); + + // When a block is inserted, the tag is only a newly used tag if the + // sector was not previously present in the cache. + // This assumes BaseTags::insertBlock does not set the valid bit. + if (sector_blk->isValid()) { + // An existing entry's replacement data is just updated + replacementPolicy->touch(sector_blk->replacementData); + } else { + // Increment tag counter + tagsInUse++; + + // A new entry resets the replacement data + replacementPolicy->reset(sector_blk->replacementData); + } +} + +CacheBlk* +SectorTags::findBlock(Addr addr, bool is_secure) const +{ + // Extract sector tag + const Addr tag = extractTag(addr); + + // The address can only be mapped to a specific location of a sector + // due to sectors being composed of contiguous-address entries + const Addr offset = extractSectorOffset(addr); + + // Find all possible sector locations for the given address + const std::vector<SectorBlk*> locations = getPossibleLocations(addr); + + // Search for block + for (const auto& sector : locations) { + auto blk = sector->blks[offset]; + if (blk->getTag() == tag && blk->isValid() && + blk->isSecure() == is_secure) { + return blk; + } + } + + // Did not find block + return nullptr; +} + +ReplaceableEntry* +SectorTags::findBlockBySetAndWay(int set, int way) const +{ + return sets[set][way]; +} + +CacheBlk* +SectorTags::findVictim(Addr addr, const bool is_secure, + std::vector<CacheBlk*>& evict_blks) const +{ + // Get all possible locations of this sector + const std::vector<SectorBlk*> sector_locations = + getPossibleLocations(addr); + + // Check if the sector this address belongs to has been allocated + Addr tag = extractTag(addr); + SectorBlk* victim_sector = nullptr; + for (const auto& sector : sector_locations){ + if ((tag == sector->getTag()) && sector->isValid() && + (is_secure == sector->isSecure())){ + victim_sector = sector; + break; + } + } + + // If the sector is not present + if (victim_sector == nullptr){ + // Choose replacement victim from replacement candidates + victim_sector = static_cast<SectorBlk*>(replacementPolicy->getVictim( + std::vector<ReplaceableEntry*>( + sector_locations.begin(), sector_locations.end()))); + } + + // Get the location of the victim block within the sector + CacheBlk* victim = victim_sector->blks[extractSectorOffset(addr)]; + + // Get evicted blocks. Blocks are only evicted if the sectors mismatch and + // the currently existing sector is valid. + if ((tag == victim_sector->getTag()) && + (is_secure == victim_sector->isSecure())){ + // It would be a hit if victim was valid, and upgrades do not call + // findVictim, so it cannot happen + assert(!victim->isValid()); + } else { + // The whole sector must be evicted to make room for the new sector + for (const auto& blk : victim_sector->blks){ + evict_blks.push_back(blk); + } + } + + SectorSubBlk* victim_cast = static_cast<SectorSubBlk*>(victim); + DPRINTF(CacheRepl, "set %x, way %x, sector offset %x: %s\n", + "selecting blk for replacement\n", victim->set, victim->way, + victim_cast->getSectorOffset()); + + return victim; +} + +Addr +SectorTags::extractTag(Addr addr) const +{ + return addr >> tagShift; +} + +int +SectorTags::extractSet(Addr addr) const +{ + return (addr >> setShift) & setMask; +} + +int +SectorTags::extractSectorOffset(Addr addr) const +{ + return (addr >> sectorShift) & sectorMask; +} + +Addr +SectorTags::regenerateBlkAddr(const CacheBlk* blk) const +{ + const SectorSubBlk* blk_cast = static_cast<const SectorSubBlk*>(blk); + return ((blk_cast->getTag() << tagShift) | ((Addr)blk->set << setShift) | + ((Addr)blk_cast->getSectorOffset() << sectorShift)); +} + +void +SectorTags::forEachBlk(std::function<void(CacheBlk &)> visitor) +{ + for (SectorSubBlk& blk : blks) { + visitor(blk); + } +} + +bool +SectorTags::anyBlk(std::function<bool(CacheBlk &)> visitor) +{ + for (SectorSubBlk& blk : blks) { + if (visitor(blk)) { + return true; + } + } + return false; +} + +SectorTags * +SectorTagsParams::create() +{ + return new SectorTags(this); +} |