src/mem/cache/tags/fa_lru.cc

   1 /*
   2  * Copyright (c) 2003-2005 The Regents of The University of Michigan
   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: Erik Hallnor
  29  */
  30
  31 /**
  32  * @file
  33  * Definitions a fully associative LRU tagstore.
  34  */
  35
  36 #include <cassert>
  37 #include <sstream>
  38
  39 #include "base/intmath.hh"
  40 #include "base/misc.hh"
  41 #include "mem/cache/tags/fa_lru.hh"
  42
  43 using namespace std;
  44
  45 FALRU::FALRU(unsigned _blkSize, unsigned _size, unsigned hit_latency)
  46     : blkSize(_blkSize), size(_size), hitLatency(hit_latency)
  47 {
  48     if (!isPowerOf2(blkSize))
  49         fatal("cache block size (in bytes) `%d' must be a power of two",
  50               blkSize);
  51     if (!(hitLatency > 0))
  52         fatal("Access latency in cycles must be at least one cycle");
  53     if (!isPowerOf2(size))
  54         fatal("Cache Size must be power of 2 for now");
  55
  56     // Track all cache sizes from 128K up by powers of 2
  57     numCaches = floorLog2(size) - 17;
  58     if (numCaches >0){
  59         cacheBoundaries = new FALRUBlk *[numCaches];
  60         cacheMask = (1 << numCaches) - 1;
  61     } else {
  62         cacheMask = 0;
  63     }
  64
  65     warmedUp = false;
  66     warmupBound = size/blkSize;
  67     numBlocks = size/blkSize;
  68
  69     blks = new FALRUBlk[numBlocks];
  70     head = &(blks[0]);
  71     tail = &(blks[numBlocks-1]);
  72
  73     head->prev = NULL;
  74     head->next = &(blks[1]);
  75     head->inCache = cacheMask;
  76
  77     tail->prev = &(blks[numBlocks-2]);
  78     tail->next = NULL;
  79     tail->inCache = 0;
  80
  81     unsigned index = (1 << 17) / blkSize;
  82     unsigned j = 0;
  83     int flags = cacheMask;
  84     for (unsigned i = 1; i < numBlocks - 1; i++) {
  85         blks[i].inCache = flags;
  86         if (i == index - 1){
  87             cacheBoundaries[j] = &(blks[i]);
  88             flags &= ~ (1<<j);
  89             ++j;
  90             index = index << 1;
  91         }
  92         blks[i].prev = &(blks[i-1]);
  93         blks[i].next = &(blks[i+1]);
  94         blks[i].isTouched = false;
  95     }
  96     assert(j == numCaches);
  97     assert(index == numBlocks);
  98     //assert(check());
  99 }
 100
 101 FALRU::~FALRU()
 102 {
 103     if (numCaches)
 104         delete[] cacheBoundaries;
 105
 106     delete[] blks;
 107 }
 108
 109 void
 110 FALRU::regStats(const string &name)
 111 {
 112     using namespace Stats;
 113     BaseTags::regStats(name);
 114     hits
 115         .init(numCaches+1)
 116         .name(name + ".falru_hits")
 117         .desc("The number of hits in each cache size.")
 118         ;
 119     misses
 120         .init(numCaches+1)
 121         .name(name + ".falru_misses")
 122         .desc("The number of misses in each cache size.")
 123         ;
 124     accesses
 125         .name(name + ".falru_accesses")
 126         .desc("The number of accesses to the FA LRU cache.")
 127         ;
 128
 129     for (unsigned i = 0; i <= numCaches; ++i) {
 130         stringstream size_str;
 131         if (i < 3){
 132             size_str << (1<<(i+7)) <<"K";
 133         } else {
 134             size_str << (1<<(i-3)) <<"M";
 135         }
 136
 137         hits.subname(i, size_str.str());
 138         hits.subdesc(i, "Hits in a " + size_str.str() +" cache");
 139         misses.subname(i, size_str.str());
 140         misses.subdesc(i, "Misses in a " + size_str.str() +" cache");
 141     }
 142 }
 143
 144 FALRUBlk *
 145 FALRU::hashLookup(Addr addr) const
 146 {
 147     tagIterator iter = tagHash.find(addr);
 148     if (iter != tagHash.end()) {
 149         return (*iter).second;
 150     }
 151     return NULL;
 152 }
 153
 154 void
 155 FALRU::invalidate(FALRU::BlkType *blk)
 156 {
 157     assert(blk);
 158     tagsInUse--;
 159 }
 160
 161 FALRUBlk*
 162 FALRU::accessBlock(Addr addr, int &lat, int context_src, int *inCache)
 163 {
 164     accesses++;
 165     int tmp_in_cache = 0;
 166     Addr blkAddr = blkAlign(addr);
 167     FALRUBlk* blk = hashLookup(blkAddr);
 168
 169     if (blk && blk->isValid()) {
 170         assert(blk->tag == blkAddr);
 171         tmp_in_cache = blk->inCache;
 172         for (unsigned i = 0; i < numCaches; i++) {
 173             if (1<<i & blk->inCache) {
 174                 hits[i]++;
 175             } else {
 176                 misses[i]++;
 177             }
 178         }
 179         hits[numCaches]++;
 180         if (blk != head){
 181             moveToHead(blk);
 182         }
 183     } else {
 184         blk = NULL;
 185         for (unsigned i = 0; i <= numCaches; ++i) {
 186             misses[i]++;
 187         }
 188     }
 189     if (inCache) {
 190         *inCache = tmp_in_cache;
 191     }
 192
 193     lat = hitLatency;
 194     //assert(check());
 195     return blk;
 196 }
 197
 198
 199 FALRUBlk*
 200 FALRU::findBlock(Addr addr) const
 201 {
 202     Addr blkAddr = blkAlign(addr);
 203     FALRUBlk* blk = hashLookup(blkAddr);
 204
 205     if (blk && blk->isValid()) {
 206         assert(blk->tag == blkAddr);
 207     } else {
 208         blk = NULL;
 209     }
 210     return blk;
 211 }
 212
 213 FALRUBlk*
 214 FALRU::findVictim(Addr addr, PacketList &writebacks)
 215 {
 216     FALRUBlk * blk = tail;
 217     assert(blk->inCache == 0);
 218     moveToHead(blk);
 219     tagHash.erase(blk->tag);
 220     tagHash[blkAlign(addr)] = blk;
 221     if (blk->isValid()) {
 222         replacements[0]++;
 223     } else {
 224         tagsInUse++;
 225         blk->isTouched = true;
 226         if (!warmedUp && tagsInUse.value() >= warmupBound) {
 227             warmedUp = true;
 228             warmupCycle = curTick();
 229         }
 230     }
 231     //assert(check());
 232     return blk;
 233 }
 234
 235 void
 236 FALRU::insertBlock(Addr addr, FALRU::BlkType *blk, int context_src)
 237 {
 238 }
 239
 240 void
 241 FALRU::moveToHead(FALRUBlk *blk)
 242 {
 243     int updateMask = blk->inCache ^ cacheMask;
 244     for (unsigned i = 0; i < numCaches; i++){
 245         if ((1<<i) & updateMask) {
 246             cacheBoundaries[i]->inCache &= ~(1<<i);
 247             cacheBoundaries[i] = cacheBoundaries[i]->prev;
 248         } else if (cacheBoundaries[i] == blk) {
 249             cacheBoundaries[i] = blk->prev;
 250         }
 251     }
 252     blk->inCache = cacheMask;
 253     if (blk != head) {
 254         if (blk == tail){
 255             assert(blk->next == NULL);
 256             tail = blk->prev;
 257             tail->next = NULL;
 258         } else {
 259             blk->prev->next = blk->next;
 260             blk->next->prev = blk->prev;
 261         }
 262         blk->next = head;
 263         blk->prev = NULL;
 264         head->prev = blk;
 265         head = blk;
 266     }
 267 }
 268
 269 bool
 270 FALRU::check()
 271 {
 272     FALRUBlk* blk = head;
 273     int size = 0;
 274     int boundary = 1<<17;
 275     int j = 0;
 276     int flags = cacheMask;
 277     while (blk) {
 278         size += blkSize;
 279         if (blk->inCache != flags) {
 280             return false;
 281         }
 282         if (size == boundary && blk != tail) {
 283             if (cacheBoundaries[j] != blk) {
 284                 return false;
 285             }
 286             flags &=~(1 << j);
 287             boundary = boundary<<1;
 288             ++j;
 289         }
 290         blk = blk->next;
 291     }
 292     return true;
 293 }
 294
 295 void
 296 FALRU::clearLocks()
 297 {
 298     for (int i = 0; i < numBlocks; i++){
 299         blks[i].clearLoadLocks();
 300     }
 301 }