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 __MEM_CACHE_TAGS_LRU_HH__
  37 #define __MEM_CACHE_TAGS_LRU_HH__
  38
  39 #include <cassert>
  40 #include <cstring>
  41 #include <list>
  42
  43 #include "mem/cache/blk.hh"
  44 #include "mem/cache/tags/base.hh"
  45 #include "mem/packet.hh"
  46
  47 class BaseCache;
  48 class CacheSet;
  49
  50
  51 /**
  52  * A LRU cache tag store.
  53  */
  54 class LRU : public BaseTags
  55 {
  56   public:
  57     /** Typedef the block type used in this tag store. */
  58     typedef CacheBlk BlkType;
  59     /** Typedef for a list of pointers to the local block class. */
  60     typedef std::list<BlkType*> BlkList;
  61
  62   protected:
  63     /** The number of sets in the cache. */
  64     const unsigned numSets;
  65     /** The number of bytes in a block. */
  66     const unsigned blkSize;
  67     /** The associativity of the cache. */
  68     const unsigned assoc;
  69     /** The hit latency. */
  70     const unsigned hitLatency;
  71
  72     /** The cache sets. */
  73     CacheSet *sets;
  74
  75     /** The cache blocks. */
  76     BlkType *blks;
  77     /** The data blocks, 1 per cache block. */
  78     uint8_t *dataBlks;
  79
  80     /** The amount to shift the address to get the set. */
  81     int setShift;
  82     /** The amount to shift the address to get the tag. */
  83     int tagShift;
  84     /** Mask out all bits that aren't part of the set index. */
  85     unsigned setMask;
  86     /** Mask out all bits that aren't part of the block offset. */
  87     unsigned blkMask;
  88
  89 public:
  90     /**
  91      * Construct and initialize this tag store.
  92      * @param _numSets The number of sets in the cache.
  93      * @param _blkSize The number of bytes in a block.
  94      * @param _assoc The associativity of the cache.
  95      * @param _hit_latency The latency in cycles for a hit.
  96      */
  97     LRU(unsigned _numSets, unsigned _blkSize, unsigned _assoc,
  98         unsigned _hit_latency);
  99
 100     /**
 101      * Destructor
 102      */
 103     virtual ~LRU();
 104
 105     /**
 106      * Return the block size.
 107      * @return the block size.
 108      */
 109     unsigned
 110     getBlockSize() const
 111     {
 112         return blkSize;
 113     }
 114
 115     /**
 116      * Return the subblock size. In the case of LRU it is always the block
 117      * size.
 118      * @return The block size.
 119      */
 120     unsigned
 121     getSubBlockSize() const
 122     {
 123         return blkSize;
 124     }
 125
 126     /**
 127      * Invalidate the given block.
 128      * @param blk The block to invalidate.
 129      */
 130     void invalidateBlk(BlkType *blk);
 131
 132     /**
 133      * Access block and update replacement data.  May not succeed, in which case
 134      * NULL pointer is returned.  This has all the implications of a cache
 135      * access and should only be used as such. Returns the access latency as a side effect.
 136      * @param addr The address to find.
 137      * @param asid The address space ID.
 138      * @param lat The access latency.
 139      * @return Pointer to the cache block if found.
 140      */
 141     BlkType* accessBlock(Addr addr, int &lat, int context_src);
 142
 143     /**
 144      * Finds the given address in the cache, do not update replacement data.
 145      * i.e. This is a no-side-effect find of a block.
 146      * @param addr The address to find.
 147      * @param asid The address space ID.
 148      * @return Pointer to the cache block if found.
 149      */
 150     BlkType* findBlock(Addr addr) const;
 151
 152     /**
 153      * Find a block to evict for the address provided.
 154      * @param addr The addr to a find a replacement candidate for.
 155      * @param writebacks List for any writebacks to be performed.
 156      * @return The candidate block.
 157      */
 158     BlkType* findVictim(Addr addr, PacketList &writebacks);
 159
 160     /**
 161      * Insert the new block into the cache.  For LRU this means inserting into
 162      * the MRU position of the set.
 163      * @param addr The address to update.
 164      * @param blk The block to update.
 165      */
 166      void insertBlock(Addr addr, BlkType *blk, int context_src);
 167
 168     /**
 169      * Generate the tag from the given address.
 170      * @param addr The address to get the tag from.
 171      * @return The tag of the address.
 172      */
 173     Addr extractTag(Addr addr) const
 174     {
 175         return (addr >> tagShift);
 176     }
 177
 178     /**
 179      * Calculate the set index from the address.
 180      * @param addr The address to get the set from.
 181      * @return The set index of the address.
 182      */
 183     int extractSet(Addr addr) const
 184     {
 185         return ((addr >> setShift) & setMask);
 186     }
 187
 188     /**
 189      * Get the block offset from an address.
 190      * @param addr The address to get the offset of.
 191      * @return The block offset.
 192      */
 193     int extractBlkOffset(Addr addr) const
 194     {
 195         return (addr & blkMask);
 196     }
 197
 198     /**
 199      * Align an address to the block size.
 200      * @param addr the address to align.
 201      * @return The block address.
 202      */
 203     Addr blkAlign(Addr addr) const
 204     {
 205         return (addr & ~(Addr)blkMask);
 206     }
 207
 208     /**
 209      * Regenerate the block address from the tag.
 210      * @param tag The tag of the block.
 211      * @param set The set of the block.
 212      * @return The block address.
 213      */
 214     Addr regenerateBlkAddr(Addr tag, unsigned set) const
 215     {
 216         return ((tag << tagShift) | ((Addr)set << setShift));
 217     }
 218
 219     /**
 220      * Return the hit latency.
 221      * @return the hit latency.
 222      */
 223     int getHitLatency() const
 224     {
 225         return hitLatency;
 226     }
 227     /**
 228      *iterated through all blocks and clear all locks
 229      *Needed to clear all lock tracking at once
 230      */
 231     virtual void clearLocks();
 232
 233     /**
 234      * Called at end of simulation to complete average block reference stats.
 235      */
 236     virtual void cleanupRefs();
 237 };
 238
 239 #endif // __MEM_CACHE_TAGS_LRU_HH__