split_lru.hh

来自「M5,一个功能强大的多处理器系统模拟器.很多针对处理器架构,性能的研究都使用它作」· HH 代码 · 共 296 行

/*
 * Copyright (c) 2004, 2005
 * The Regents of The University of Michigan
 * All Rights Reserved
 *
 * This code is part of the M5 simulator.
 *
 * Permission is granted to use, copy, create derivative works and
 * redistribute this software and such derivative works for any
 * purpose, so long as the copyright notice above, this grant of
 * permission, and the disclaimer below appear in all copies made; and
 * so long as the name of The University of Michigan is not used in
 * any advertising or publicity pertaining to the use or distribution
 * of this software without specific, written prior authorization.
 *
 * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION FROM THE
 * UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY PURPOSE, AND
 * WITHOUT WARRANTY BY THE UNIVERSITY OF MICHIGAN OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE. THE REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE
 * LIABLE FOR ANY DAMAGES, INCLUDING DIRECT, SPECIAL, INDIRECT,
 * INCIDENTAL, OR CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM
 * ARISING OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
 * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGES.
 *
 * Authors: Lisa R. Hsu
 */

/**
 * @file
 * Declaration of a LRU tag store for a partitioned cache.
 */

#ifndef __SPLIT_LRU_HH__
#define __SPLIT_LRU_HH__

#include <cstring>
#include <list>

#include "mem/cache/blk.hh" // base class
#include "mem/cache/tags/split_blk.hh"
#include "mem/packet.hh" // for inlined functions
#include <assert.h>
#include "mem/cache/tags/base.hh"

class BaseCache;

/**
 * An associative set of cache blocks.
 */

class SplitCacheSet
{
  public:
    /** The associativity of this set. */
    int assoc;

    /** Cache blocks in this set, maintained in LRU order 0 = MRU. */
    SplitBlk **blks;

    /**
     * Find a block matching the tag in this set.
     * @param asid The address space ID.
     * @param tag The Tag to find.
     * @return Pointer to the block if found.
     */
    SplitBlk* findBlk(Addr tag) const;

    /**
     * Move the given block to the head of the list.
     * @param blk The block to move.
     */
    void moveToHead(SplitBlk *blk);
};

/**
 * A LRU cache tag store.
 */
class SplitLRU : public BaseTags
{
  public:
    /** Typedef the block type used in this tag store. */
    typedef SplitBlk BlkType;
    /** Typedef for a list of pointers to the local block class. */
    typedef std::list<SplitBlk*> BlkList;
  protected:
    /** The number of sets in the cache. */
    const int numSets;
    /** The number of bytes in a block. */
    const int blkSize;
    /** The associativity of the cache. */
    const int assoc;
    /** The hit latency. */
    const int hitLatency;
    /** indicator for which partition this is */
    const int part;

    /** The cache sets. */
    SplitCacheSet *sets;

    /** The cache blocks. */
    SplitBlk *blks;
    /** The data blocks, 1 per cache block. */
    uint8_t *dataBlks;

    /** The amount to shift the address to get the set. */
    int setShift;
    /** The amount to shift the address to get the tag. */
    int tagShift;
    /** Mask out all bits that aren't part of the set index. */
    unsigned setMask;
    /** Mask out all bits that aren't part of the block offset. */
    unsigned blkMask;

    /** number of hits in this partition */
    Stats::Scalar<> hits;
    /** number of blocks brought into this partition (i.e. misses) */
    Stats::Scalar<> misses;

public:
    /**
     * Construct and initialize this tag store.
     * @param _numSets The number of sets in the cache.
     * @param _blkSize The number of bytes in a block.
     * @param _assoc The associativity of the cache.
     * @param _hit_latency The latency in cycles for a hit.
     */
    SplitLRU(int _numSets, int _blkSize, int _assoc, int _hit_latency, int _part);

    /**
     * Destructor
     */
    virtual ~SplitLRU();

    /**
     * Register the statistics for this object
     * @param name The name to precede the stat
     */
    void regStats(const std::string &name);

    /**
     * Return the block size.
     * @return the block size.
     */
    int getBlockSize()
    {
        return blkSize;
    }

    /**
     * Return the subblock size. In the case of LRU it is always the block
     * size.
     * @return The block size.
     */
    int getSubBlockSize()
    {
        return blkSize;
    }

    /**
     * Search for the address in the cache.
     * @param asid The address space ID.
     * @param addr The address to find.
     * @return True if the address is in the cache.
     */
    bool probe(Addr addr) const;

    /**
     * Invalidate the given block.
     * @param blk The block to invalidate.
     */
    void invalidateBlk(BlkType *blk);

    /**
     * Finds the given address in the cache and update replacement data.
     * Returns the access latency as a side effect.
     * @param addr The address to find.
     * @param asid The address space ID.
     * @param lat The access latency.
     * @return Pointer to the cache block if found.
     */
    SplitBlk* findBlock(Addr addr, int &lat);

    /**
     * Finds the given address in the cache, do not update replacement data.
     * @param addr The address to find.
     * @param asid The address space ID.
     * @return Pointer to the cache block if found.
     */
    SplitBlk* findBlock(Addr addr) const;

    /**
     * Find a replacement block for the address provided.
     * @param pkt The request to a find a replacement candidate for.
     * @param writebacks List for any writebacks to be performed.
     * @return The block to place the replacement in.
     */
    SplitBlk* findReplacement(Addr addr, PacketList &writebacks);

    /**
     * Generate the tag from the given address.
     * @param addr The address to get the tag from.
     * @return The tag of the address.
     */
    Addr extractTag(Addr addr) const
    {
        return (addr >> tagShift);
    }

    /**
     * Calculate the set index from the address.
     * @param addr The address to get the set from.
     * @return The set index of the address.
     */
    int extractSet(Addr addr) const
    {
        return ((addr >> setShift) & setMask);
    }

    /**
     * Get the block offset from an address.
     * @param addr The address to get the offset of.
     * @return The block offset.
     */
    int extractBlkOffset(Addr addr) const
    {
        return (addr & blkMask);
    }

    /**
     * Align an address to the block size.
     * @param addr the address to align.
     * @return The block address.
     */
    Addr blkAlign(Addr addr) const
    {
        return (addr & ~(Addr)blkMask);
    }

    /**
     * Regenerate the block address from the tag.
     * @param tag The tag of the block.
     * @param set The set of the block.
     * @return The block address.
     */
    Addr regenerateBlkAddr(Addr tag, unsigned set) const
    {
        return ((tag << tagShift) | ((Addr)set << setShift));
    }

    /**
     * Return the hit latency.
     * @return the hit latency.
     */
    int getHitLatency() const
    {
        return hitLatency;
    }

    /**
     * Read the data out of the internal storage of the given cache block.
     * @param blk The cache block to read.
     * @param data The buffer to read the data into.
     * @return The cache block's data.
     */
    void readData(SplitBlk *blk, uint8_t *data)
    {
        std::memcpy(data, blk->data, blk->size);
    }

    /**
     * Write data into the internal storage of the given cache block. Since in
     * LRU does not store data differently this just needs to update the size.
     * @param blk The cache block to write.
     * @param data The data to write.
     * @param size The number of bytes to write.
     * @param writebacks A list for any writebacks to be performed. May be
     * needed when writing to a compressed block.
     */
    void writeData(SplitBlk *blk, uint8_t *data, int size,
                   PacketList & writebacks)
    {
        assert(size <= blkSize);
        blk->size = size;
    }

    /**
     * Called at end of simulation to complete average block reference stats.
     */
    virtual void cleanupRefs();
};

#endif