284 lines
7.5 KiB
C++
284 lines
7.5 KiB
C++
/*
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* Copyright (c) 2004-2005 The Regents of The University of Michigan
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Authors: Lisa Hsu
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*/
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/**
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* @file
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* Definitions of LRU tag store for a partitioned cache.
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*/
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#include <string>
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#include "mem/cache/base_cache.hh"
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#include "base/intmath.hh"
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#include "mem/cache/tags/split_lru.hh"
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#include "sim/root.hh"
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using namespace std;
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SplitBlk*
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SplitCacheSet::findBlk(Addr tag) const
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{
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for (int i = 0; i < assoc; ++i) {
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if (blks[i]->tag == tag && blks[i]->isValid()) {
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return blks[i];
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}
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}
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return 0;
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}
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void
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SplitCacheSet::moveToHead(SplitBlk *blk)
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{
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// nothing to do if blk is already head
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if (blks[0] == blk)
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return;
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// write 'next' block into blks[i], moving up from MRU toward LRU
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// until we overwrite the block we moved to head.
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// start by setting up to write 'blk' into blks[0]
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int i = 0;
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SplitBlk *next = blk;
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do {
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assert(i < assoc);
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// swap blks[i] and next
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SplitBlk *tmp = blks[i];
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blks[i] = next;
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next = tmp;
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++i;
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} while (next != blk);
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}
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// create and initialize a LRU/MRU cache structure
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SplitLRU::SplitLRU(int _numSets, int _blkSize, int _assoc, int _hit_latency, int _part) :
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numSets(_numSets), blkSize(_blkSize), assoc(_assoc), hitLatency(_hit_latency), part(_part)
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{
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// Check parameters
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if (blkSize < 4 || !isPowerOf2(blkSize)) {
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fatal("Block size must be at least 4 and a power of 2");
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}
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if (numSets <= 0 || !isPowerOf2(numSets)) {
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fatal("# of sets must be non-zero and a power of 2");
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}
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if (assoc <= 0) {
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fatal("associativity must be greater than zero");
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}
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if (hitLatency <= 0) {
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fatal("access latency must be greater than zero");
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}
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SplitBlk *blk;
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int i, j, blkIndex;
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blkMask = blkSize - 1;
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setShift = floorLog2(blkSize);
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setMask = numSets - 1;
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tagShift = setShift + floorLog2(numSets);
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warmedUp = false;
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/** @todo Make warmup percentage a parameter. */
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warmupBound = numSets * assoc;
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sets = new SplitCacheSet[numSets];
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blks = new SplitBlk[numSets * assoc];
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// allocate data storage in one big chunk
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dataBlks = new uint8_t[numSets*assoc*blkSize];
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blkIndex = 0; // index into blks array
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for (i = 0; i < numSets; ++i) {
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sets[i].assoc = assoc;
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sets[i].blks = new SplitBlk*[assoc];
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// link in the data blocks
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for (j = 0; j < assoc; ++j) {
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// locate next cache block
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blk = &blks[blkIndex];
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blk->data = &dataBlks[blkSize*blkIndex];
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++blkIndex;
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// invalidate new cache block
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blk->status = 0;
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//EGH Fix Me : do we need to initialize blk?
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// Setting the tag to j is just to prevent long chains in the hash
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// table; won't matter because the block is invalid
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blk->tag = j;
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blk->whenReady = 0;
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blk->isTouched = false;
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blk->size = blkSize;
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sets[i].blks[j]=blk;
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blk->set = i;
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blk->part = part;
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}
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}
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}
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SplitLRU::~SplitLRU()
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{
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delete [] dataBlks;
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delete [] blks;
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delete [] sets;
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}
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void
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SplitLRU::regStats(const std::string &name)
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{
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BaseTags::regStats(name);
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hits
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.name(name + ".hits")
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.desc("number of hits on this partition")
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.precision(0)
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;
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misses
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.name(name + ".misses")
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.desc("number of misses in this partition")
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.precision(0)
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;
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}
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// probe cache for presence of given block.
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bool
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SplitLRU::probe(Addr addr) const
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{
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// return(findBlock(Read, addr, asid) != 0);
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Addr tag = extractTag(addr);
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unsigned myset = extractSet(addr);
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SplitBlk *blk = sets[myset].findBlk(tag);
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return (blk != NULL); // true if in cache
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}
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SplitBlk*
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SplitLRU::findBlock(Addr addr, int &lat)
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{
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Addr tag = extractTag(addr);
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unsigned set = extractSet(addr);
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SplitBlk *blk = sets[set].findBlk(tag);
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lat = hitLatency;
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if (blk != NULL) {
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// move this block to head of the MRU list
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sets[set].moveToHead(blk);
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if (blk->whenReady > curTick && blk->whenReady - curTick > hitLatency){
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lat = blk->whenReady - curTick;
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}
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blk->refCount += 1;
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hits++;
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}
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return blk;
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}
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SplitBlk*
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SplitLRU::findBlock(Packet * &pkt, int &lat)
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{
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Addr addr = pkt->getAddr();
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Addr tag = extractTag(addr);
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unsigned set = extractSet(addr);
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SplitBlk *blk = sets[set].findBlk(tag);
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lat = hitLatency;
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if (blk != NULL) {
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// move this block to head of the MRU list
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sets[set].moveToHead(blk);
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if (blk->whenReady > curTick && blk->whenReady - curTick > hitLatency){
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lat = blk->whenReady - curTick;
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}
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blk->refCount += 1;
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hits++;
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}
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return blk;
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}
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SplitBlk*
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SplitLRU::findBlock(Addr addr) const
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{
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Addr tag = extractTag(addr);
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unsigned set = extractSet(addr);
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SplitBlk *blk = sets[set].findBlk(tag);
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return blk;
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}
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SplitBlk*
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SplitLRU::findReplacement(Packet * &pkt, PacketList &writebacks,
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BlkList &compress_blocks)
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{
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unsigned set = extractSet(pkt->getAddr());
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// grab a replacement candidate
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SplitBlk *blk = sets[set].blks[assoc-1];
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sets[set].moveToHead(blk);
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if (blk->isValid()) {
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replacements[0]++;
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totalRefs += blk->refCount;
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++sampledRefs;
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blk->refCount = 0;
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} else if (!blk->isTouched) {
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tagsInUse++;
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blk->isTouched = true;
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if (!warmedUp && tagsInUse.value() >= warmupBound) {
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warmedUp = true;
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warmupCycle = curTick;
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}
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}
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misses++;
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return blk;
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}
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void
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SplitLRU::invalidateBlk(Addr addr)
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{
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SplitBlk *blk = findBlock(addr);
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if (blk) {
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blk->status = 0;
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blk->isTouched = false;
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tagsInUse--;
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}
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}
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void
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SplitLRU::cleanupRefs()
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{
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for (int i = 0; i < numSets*assoc; ++i) {
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if (blks[i].isValid()) {
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totalRefs += blks[i].refCount;
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++sampledRefs;
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}
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}
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}
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