src/mem/cache/tags/lru.hh

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