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