src/mem/cache/tags/split_lru.hh

   1 /*
   2  * Copyright (c) 2004-2005 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: Lisa Hsu
  29  */
  30
  31 /**
  32  * @file
  33  * Declaration of a LRU tag store for a partitioned cache.
  34  */
  35
  36 #ifndef __SPLIT_LRU_HH__
  37 #define __SPLIT_LRU_HH__
  38
  39 #include <cstring>
  40 #include <list>
  41
  42 #include "mem/cache/cache_blk.hh" // base class
  43 #include "mem/cache/tags/split_blk.hh"
  44 #include "mem/packet.hh" // for inlined functions
  45 #include <assert.h>
  46 #include "mem/cache/tags/base_tags.hh"
  47
  48 class BaseCache;
  49
  50 /**
  51  * An associative set of cache blocks.
  52  */
  53
  54 class SplitCacheSet
  55 {
  56   public:
  57     /** The associativity of this set. */
  58     int assoc;
  59
  60     /** Cache blocks in this set, maintained in LRU order 0 = MRU. */
  61     SplitBlk **blks;
  62
  63     /**
  64      * Find a block matching the tag in this set.
  65      * @param asid The address space ID.
  66      * @param tag The Tag to find.
  67      * @return Pointer to the block if found.
  68      */
  69     SplitBlk* findBlk(Addr tag) const;
  70
  71     /**
  72      * Move the given block to the head of the list.
  73      * @param blk The block to move.
  74      */
  75     void moveToHead(SplitBlk *blk);
  76 };
  77
  78 /**
  79  * A LRU cache tag store.
  80  */
  81 class SplitLRU : public BaseTags
  82 {
  83   public:
  84     /** Typedef the block type used in this tag store. */
  85     typedef SplitBlk BlkType;
  86     /** Typedef for a list of pointers to the local block class. */
  87     typedef std::list<SplitBlk*> BlkList;
  88   protected:
  89     /** The number of sets in the cache. */
  90     const int numSets;
  91     /** The number of bytes in a block. */
  92     const int blkSize;
  93     /** The associativity of the cache. */
  94     const int assoc;
  95     /** The hit latency. */
  96     const int hitLatency;
  97     /** indicator for which partition this is */
  98     const int part;
  99
 100     /** The cache sets. */
 101     SplitCacheSet *sets;
 102
 103     /** The cache blocks. */
 104     SplitBlk *blks;
 105     /** The data blocks, 1 per cache block. */
 106     uint8_t *dataBlks;
 107
 108     /** The amount to shift the address to get the set. */
 109     int setShift;
 110     /** The amount to shift the address to get the tag. */
 111     int tagShift;
 112     /** Mask out all bits that aren't part of the set index. */
 113     unsigned setMask;
 114     /** Mask out all bits that aren't part of the block offset. */
 115     unsigned blkMask;
 116
 117     /** number of hits in this partition */
 118     Stats::Scalar<> hits;
 119     /** number of blocks brought into this partition (i.e. misses) */
 120     Stats::Scalar<> misses;
 121
 122 public:
 123     /**
 124      * Construct and initialize this tag store.
 125      * @param _numSets The number of sets in the cache.
 126      * @param _blkSize The number of bytes in a block.
 127      * @param _assoc The associativity of the cache.
 128      * @param _hit_latency The latency in cycles for a hit.
 129      */
 130     SplitLRU(int _numSets, int _blkSize, int _assoc, int _hit_latency, int _part);
 131
 132     /**
 133      * Destructor
 134      */
 135     virtual ~SplitLRU();
 136
 137     /**
 138      * Register the statistics for this object
 139      * @param name The name to precede the stat
 140      */
 141     void regStats(const std::string &name);
 142
 143     /**
 144      * Return the block size.
 145      * @return the block size.
 146      */
 147     int getBlockSize()
 148     {
 149         return blkSize;
 150     }
 151
 152     /**
 153      * Return the subblock size. In the case of LRU it is always the block
 154      * size.
 155      * @return The block size.
 156      */
 157     int getSubBlockSize()
 158     {
 159         return blkSize;
 160     }
 161
 162     /**
 163      * Search for the address in the cache.
 164      * @param asid The address space ID.
 165      * @param addr The address to find.
 166      * @return True if the address is in the cache.
 167      */
 168     bool probe(Addr addr) const;
 169
 170     /**
 171      * Invalidate the given block.
 172      * @param blk The block to invalidate.
 173      */
 174     void invalidateBlk(BlkType *blk);
 175
 176     /**
 177      * Finds the given address in the cache and update replacement data.
 178      * Returns the access latency as a side effect.
 179      * @param addr The address to find.
 180      * @param asid The address space ID.
 181      * @param lat The access latency.
 182      * @return Pointer to the cache block if found.
 183      */
 184     SplitBlk* findBlock(Addr addr, int &lat);
 185
 186     /**
 187      * Finds the given address in the cache, do not update replacement data.
 188      * @param addr The address to find.
 189      * @param asid The address space ID.
 190      * @return Pointer to the cache block if found.
 191      */
 192     SplitBlk* findBlock(Addr addr) const;
 193
 194     /**
 195      * Find a replacement block for the address provided.
 196      * @param pkt The request to a find a replacement candidate for.
 197      * @param writebacks List for any writebacks to be performed.
 198      * @param compress_blocks List of blocks to compress, for adaptive comp.
 199      * @return The block to place the replacement in.
 200      */
 201     SplitBlk* findReplacement(PacketPtr &pkt, PacketList &writebacks,
 202                             BlkList &compress_blocks);
 203
 204     /**
 205      * Generate the tag from the given address.
 206      * @param addr The address to get the tag from.
 207      * @return The tag of the address.
 208      */
 209     Addr extractTag(Addr addr) const
 210     {
 211         return (addr >> tagShift);
 212     }
 213
 214     /**
 215      * Generate the tag from the given address.
 216      * @param addr The address to get the tag from.
 217      * @param blk Ignored.
 218      * @return The tag of the address.
 219      */
 220     Addr extractTag(Addr addr, SplitBlk *blk) const
 221     {
 222         return (addr >> tagShift);
 223     }
 224
 225     /**
 226      * Calculate the set index from the address.
 227      * @param addr The address to get the set from.
 228      * @return The set index of the address.
 229      */
 230     int extractSet(Addr addr) const
 231     {
 232         return ((addr >> setShift) & setMask);
 233     }
 234
 235     /**
 236      * Get the block offset from an address.
 237      * @param addr The address to get the offset of.
 238      * @return The block offset.
 239      */
 240     int extractBlkOffset(Addr addr) const
 241     {
 242         return (addr & blkMask);
 243     }
 244
 245     /**
 246      * Align an address to the block size.
 247      * @param addr the address to align.
 248      * @return The block address.
 249      */
 250     Addr blkAlign(Addr addr) const
 251     {
 252         return (addr & ~(Addr)blkMask);
 253     }
 254
 255     /**
 256      * Regenerate the block address from the tag.
 257      * @param tag The tag of the block.
 258      * @param set The set of the block.
 259      * @return The block address.
 260      */
 261     Addr regenerateBlkAddr(Addr tag, unsigned set) const
 262     {
 263         return ((tag << tagShift) | ((Addr)set << setShift));
 264     }
 265
 266     /**
 267      * Return the hit latency.
 268      * @return the hit latency.
 269      */
 270     int getHitLatency() const
 271     {
 272         return hitLatency;
 273     }
 274
 275     /**
 276      * Read the data out of the internal storage of the given cache block.
 277      * @param blk The cache block to read.
 278      * @param data The buffer to read the data into.
 279      * @return The cache block's data.
 280      */
 281     void readData(SplitBlk *blk, uint8_t *data)
 282     {
 283         std::memcpy(data, blk->data, blk->size);
 284     }
 285
 286     /**
 287      * Write data into the internal storage of the given cache block. Since in
 288      * LRU does not store data differently this just needs to update the size.
 289      * @param blk The cache block to write.
 290      * @param data The data to write.
 291      * @param size The number of bytes to write.
 292      * @param writebacks A list for any writebacks to be performed. May be
 293      * needed when writing to a compressed block.
 294      */
 295     void writeData(SplitBlk *blk, uint8_t *data, int size,
 296                    PacketList & writebacks)
 297     {
 298         assert(size <= blkSize);
 299         blk->size = size;
 300     }
 301
 302     /**
 303      * Called at end of simulation to complete average block reference stats.
 304      */
 305     virtual void cleanupRefs();
 306 };
 307
 308 #endif