src/mem/cache/base.hh - arm/gem5 - Git at Google

 /*
  * Copyright (c) 2012-2013, 2015-2016 ARM Limited
  * All rights reserved.
  *
  * The license below extends only to copyright in the software and shall
  * not be construed as granting a license to any other intellectual
  * property including but not limited to intellectual property relating
  * to a hardware implementation of the functionality of the software
  * licensed hereunder.  You may use the software subject to the license
  * terms below provided that you ensure that this notice is replicated
  * unmodified and in its entirety in all distributions of the software,
  * modified or unmodified, in source code or in binary form.
  *
  * Copyright (c) 2003-2005 The Regents of The University of Michigan
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met: redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer;
  * redistributions in binary form must reproduce the above copyright
  * notice, this list of conditions and the following disclaimer in the
  * documentation and/or other materials provided with the distribution;
  * neither the name of the copyright holders nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * Authors: Erik Hallnor
  *          Steve Reinhardt
  *          Ron Dreslinski
  */

 /**
  * @file
  * Declares a basic cache interface BaseCache.
  */

 #ifndef __MEM_CACHE_BASE_HH__
 #define __MEM_CACHE_BASE_HH__

 #include <algorithm>
 #include <list>
 #include <string>
 #include <vector>

 #include "base/misc.hh"
 #include "base/statistics.hh"
 #include "base/trace.hh"
 #include "base/types.hh"
 #include "debug/Cache.hh"
 #include "debug/CachePort.hh"
 #include "mem/cache/mshr_queue.hh"
 #include "mem/cache/write_queue.hh"
 #include "mem/mem_object.hh"
 #include "mem/packet.hh"
 #include "mem/qport.hh"
 #include "mem/request.hh"
 #include "params/BaseCache.hh"
 #include "sim/eventq.hh"
 #include "sim/full_system.hh"
 #include "sim/sim_exit.hh"
 #include "sim/system.hh"

 /**
  * A basic cache interface. Implements some common functions for speed.
  */
 class BaseCache : public MemObject
 {
   protected:
     /**
      * Indexes to enumerate the MSHR queues.
      */
     enum MSHRQueueIndex {
         MSHRQueue_MSHRs,
         MSHRQueue_WriteBuffer
     };

   public:
     /**
      * Reasons for caches to be blocked.
      */
     enum BlockedCause {
         Blocked_NoMSHRs = MSHRQueue_MSHRs,
         Blocked_NoWBBuffers = MSHRQueue_WriteBuffer,
         Blocked_NoTargets,
         NUM_BLOCKED_CAUSES
     };

   protected:

     /**
      * A cache master port is used for the memory-side port of the
      * cache, and in addition to the basic timing port that only sends
      * response packets through a transmit list, it also offers the
      * ability to schedule and send request packets (requests &
      * writebacks). The send event is scheduled through schedSendEvent,
      * and the sendDeferredPacket of the timing port is modified to
      * consider both the transmit list and the requests from the MSHR.
      */
     class CacheMasterPort : public QueuedMasterPort
     {

       public:

         /**
          * Schedule a send of a request packet (from the MSHR). Note
          * that we could already have a retry outstanding.
          */
         void schedSendEvent(Tick time)
         {
             DPRINTF(CachePort, "Scheduling send event at %llu\n", time);
             reqQueue.schedSendEvent(time);
         }

       protected:

         CacheMasterPort(const std::string &_name, BaseCache *_cache,
                         ReqPacketQueue &_reqQueue,
                         SnoopRespPacketQueue &_snoopRespQueue) :
             QueuedMasterPort(_name, _cache, _reqQueue, _snoopRespQueue)
         { }

         /**
          * Memory-side port always snoops.
          *
          * @return always true
          */
         virtual bool isSnooping() const { return true; }
     };

     /**
      * A cache slave port is used for the CPU-side port of the cache,
      * and it is basically a simple timing port that uses a transmit
      * list for responses to the CPU (or connected master). In
      * addition, it has the functionality to block the port for
      * incoming requests. If blocked, the port will issue a retry once
      * unblocked.
      */
     class CacheSlavePort : public QueuedSlavePort
     {

       public:

         /** Do not accept any new requests. */
         void setBlocked();

         /** Return to normal operation and accept new requests. */
         void clearBlocked();

         bool isBlocked() const { return blocked; }

       protected:

         CacheSlavePort(const std::string &_name, BaseCache *_cache,
                        const std::string &_label);

         /** A normal packet queue used to store responses. */
         RespPacketQueue queue;

         bool blocked;

         bool mustSendRetry;

       private:

         void processSendRetry();

         EventFunctionWrapper sendRetryEvent;

     };

     CacheSlavePort *cpuSidePort;
     CacheMasterPort *memSidePort;

   protected:

     /** Miss status registers */
     MSHRQueue mshrQueue;

     /** Write/writeback buffer */
     WriteQueue writeBuffer;

     /**
      * Mark a request as in service (sent downstream in the memory
      * system), effectively making this MSHR the ordering point.
      */
     void markInService(MSHR *mshr, bool pending_modified_resp)
     {
         bool wasFull = mshrQueue.isFull();
         mshrQueue.markInService(mshr, pending_modified_resp);

         if (wasFull && !mshrQueue.isFull()) {
             clearBlocked(Blocked_NoMSHRs);
         }
     }

     void markInService(WriteQueueEntry *entry)
     {
         bool wasFull = writeBuffer.isFull();
         writeBuffer.markInService(entry);

         if (wasFull && !writeBuffer.isFull()) {
             clearBlocked(Blocked_NoWBBuffers);
         }
     }

     /**
      * Determine if we should allocate on a fill or not.
      *
      * @param cmd Packet command being added as an MSHR target
      *
      * @return Whether we should allocate on a fill or not
      */
     virtual bool allocOnFill(MemCmd cmd) const = 0;

     /**
      * Write back dirty blocks in the cache using functional accesses.
      */
     virtual void memWriteback() override = 0;
     /**
      * Invalidates all blocks in the cache.
      *
      * @warn Dirty cache lines will not be written back to
      * memory. Make sure to call functionalWriteback() first if you
      * want the to write them to memory.
      */
     virtual void memInvalidate() override = 0;
     /**
      * Determine if there are any dirty blocks in the cache.
      *
      * \return true if at least one block is dirty, false otherwise.
      */
     virtual bool isDirty() const = 0;

     /**
      * Determine if an address is in the ranges covered by this
      * cache. This is useful to filter snoops.
      *
      * @param addr Address to check against
      *
      * @return If the address in question is in range
      */
     bool inRange(Addr addr) const;

     /** Block size of this cache */
     const unsigned blkSize;

     /**
      * The latency of tag lookup of a cache. It occurs when there is
      * an access to the cache.
      */
     const Cycles lookupLatency;

     /**
      * The latency of data access of a cache. It occurs when there is
      * an access to the cache.
      */
     const Cycles dataLatency;

     /**
      * This is the forward latency of the cache. It occurs when there
      * is a cache miss and a request is forwarded downstream, in
      * particular an outbound miss.
      */
     const Cycles forwardLatency;

     /** The latency to fill a cache block */
     const Cycles fillLatency;

     /**
      * The latency of sending reponse to its upper level cache/core on
      * a linefill. The responseLatency parameter captures this
      * latency.
      */
     const Cycles responseLatency;

     /** The number of targets for each MSHR. */
     const int numTarget;

     /** Do we forward snoops from mem side port through to cpu side port? */
     bool forwardSnoops;

     /**
      * Is this cache read only, for example the instruction cache, or
      * table-walker cache. A cache that is read only should never see
      * any writes, and should never get any dirty data (and hence
      * never have to do any writebacks).
      */
     const bool isReadOnly;

     /**
      * Bit vector of the blocking reasons for the access path.
      * @sa #BlockedCause
      */
     uint8_t blocked;

     /** Increasing order number assigned to each incoming request. */
     uint64_t order;

     /** Stores time the cache blocked for statistics. */
     Cycles blockedCycle;

     /** Pointer to the MSHR that has no targets. */
     MSHR *noTargetMSHR;

     /** The number of misses to trigger an exit event. */
     Counter missCount;

     /**
      * The address range to which the cache responds on the CPU side.
      * Normally this is all possible memory addresses. */
     const AddrRangeList addrRanges;

   public:
     /** System we are currently operating in. */
     System *system;

     // Statistics
     /**
      * @addtogroup CacheStatistics
      * @{
      */

     /** Number of hits per thread for each type of command.
         @sa Packet::Command */
     Stats::Vector hits[MemCmd::NUM_MEM_CMDS];
     /** Number of hits for demand accesses. */
     Stats::Formula demandHits;
     /** Number of hit for all accesses. */
     Stats::Formula overallHits;

     /** Number of misses per thread for each type of command.
         @sa Packet::Command */
     Stats::Vector misses[MemCmd::NUM_MEM_CMDS];
     /** Number of misses for demand accesses. */
     Stats::Formula demandMisses;
     /** Number of misses for all accesses. */
     Stats::Formula overallMisses;

     /**
      * Total number of cycles per thread/command spent waiting for a miss.
      * Used to calculate the average miss latency.
      */
     Stats::Vector missLatency[MemCmd::NUM_MEM_CMDS];
     /** Total number of cycles spent waiting for demand misses. */
     Stats::Formula demandMissLatency;
     /** Total number of cycles spent waiting for all misses. */
     Stats::Formula overallMissLatency;

     /** The number of accesses per command and thread. */
     Stats::Formula accesses[MemCmd::NUM_MEM_CMDS];
     /** The number of demand accesses. */
     Stats::Formula demandAccesses;
     /** The number of overall accesses. */
     Stats::Formula overallAccesses;

     /** The miss rate per command and thread. */
     Stats::Formula missRate[MemCmd::NUM_MEM_CMDS];
     /** The miss rate of all demand accesses. */
     Stats::Formula demandMissRate;
     /** The miss rate for all accesses. */
     Stats::Formula overallMissRate;

     /** The average miss latency per command and thread. */
     Stats::Formula avgMissLatency[MemCmd::NUM_MEM_CMDS];
     /** The average miss latency for demand misses. */
     Stats::Formula demandAvgMissLatency;
     /** The average miss latency for all misses. */
     Stats::Formula overallAvgMissLatency;

     /** The total number of cycles blocked for each blocked cause. */
     Stats::Vector blocked_cycles;
     /** The number of times this cache blocked for each blocked cause. */
     Stats::Vector blocked_causes;

     /** The average number of cycles blocked for each blocked cause. */
     Stats::Formula avg_blocked;

     /** The number of times a HW-prefetched block is evicted w/o reference. */
     Stats::Scalar unusedPrefetches;

     /** Number of blocks written back per thread. */
     Stats::Vector writebacks;

     /** Number of misses that hit in the MSHRs per command and thread. */
     Stats::Vector mshr_hits[MemCmd::NUM_MEM_CMDS];
     /** Demand misses that hit in the MSHRs. */
     Stats::Formula demandMshrHits;
     /** Total number of misses that hit in the MSHRs. */
     Stats::Formula overallMshrHits;

     /** Number of misses that miss in the MSHRs, per command and thread. */
     Stats::Vector mshr_misses[MemCmd::NUM_MEM_CMDS];
     /** Demand misses that miss in the MSHRs. */
     Stats::Formula demandMshrMisses;
     /** Total number of misses that miss in the MSHRs. */
     Stats::Formula overallMshrMisses;

     /** Number of misses that miss in the MSHRs, per command and thread. */
     Stats::Vector mshr_uncacheable[MemCmd::NUM_MEM_CMDS];
     /** Total number of misses that miss in the MSHRs. */
     Stats::Formula overallMshrUncacheable;

     /** Total cycle latency of each MSHR miss, per command and thread. */
     Stats::Vector mshr_miss_latency[MemCmd::NUM_MEM_CMDS];
     /** Total cycle latency of demand MSHR misses. */
     Stats::Formula demandMshrMissLatency;
     /** Total cycle latency of overall MSHR misses. */
     Stats::Formula overallMshrMissLatency;

     /** Total cycle latency of each MSHR miss, per command and thread. */
     Stats::Vector mshr_uncacheable_lat[MemCmd::NUM_MEM_CMDS];
     /** Total cycle latency of overall MSHR misses. */
     Stats::Formula overallMshrUncacheableLatency;

 #if 0
     /** The total number of MSHR accesses per command and thread. */
     Stats::Formula mshrAccesses[MemCmd::NUM_MEM_CMDS];
     /** The total number of demand MSHR accesses. */
     Stats::Formula demandMshrAccesses;
     /** The total number of MSHR accesses. */
     Stats::Formula overallMshrAccesses;
 #endif

     /** The miss rate in the MSHRs pre command and thread. */
     Stats::Formula mshrMissRate[MemCmd::NUM_MEM_CMDS];
     /** The demand miss rate in the MSHRs. */
     Stats::Formula demandMshrMissRate;
     /** The overall miss rate in the MSHRs. */
     Stats::Formula overallMshrMissRate;

     /** The average latency of an MSHR miss, per command and thread. */
     Stats::Formula avgMshrMissLatency[MemCmd::NUM_MEM_CMDS];
     /** The average latency of a demand MSHR miss. */
     Stats::Formula demandAvgMshrMissLatency;
     /** The average overall latency of an MSHR miss. */
     Stats::Formula overallAvgMshrMissLatency;

     /** The average latency of an MSHR miss, per command and thread. */
     Stats::Formula avgMshrUncacheableLatency[MemCmd::NUM_MEM_CMDS];
     /** The average overall latency of an MSHR miss. */
     Stats::Formula overallAvgMshrUncacheableLatency;

     /**
      * @}
      */

     /**
      * Register stats for this object.
      */
     virtual void regStats() override;

   public:
     BaseCache(const BaseCacheParams *p, unsigned blk_size);
     ~BaseCache() {}

     virtual void init() override;

     virtual BaseMasterPort &getMasterPort(const std::string &if_name,
                                           PortID idx = InvalidPortID) override;
     virtual BaseSlavePort &getSlavePort(const std::string &if_name,
                                         PortID idx = InvalidPortID) override;

     /**
      * Query block size of a cache.
      * @return  The block size
      */
     unsigned
     getBlockSize() const
     {
         return blkSize;
     }

     const AddrRangeList &getAddrRanges() const { return addrRanges; }

     MSHR *allocateMissBuffer(PacketPtr pkt, Tick time, bool sched_send = true)
     {
         MSHR *mshr = mshrQueue.allocate(pkt->getBlockAddr(blkSize), blkSize,
                                         pkt, time, order++,
                                         allocOnFill(pkt->cmd));

         if (mshrQueue.isFull()) {
             setBlocked((BlockedCause)MSHRQueue_MSHRs);
         }

         if (sched_send) {
             // schedule the send
             schedMemSideSendEvent(time);
         }

         return mshr;
     }

     void allocateWriteBuffer(PacketPtr pkt, Tick time)
     {
         // should only see writes or clean evicts here
         assert(pkt->isWrite() || pkt->cmd == MemCmd::CleanEvict);

         Addr blk_addr = pkt->getBlockAddr(blkSize);

         WriteQueueEntry *wq_entry =
             writeBuffer.findMatch(blk_addr, pkt->isSecure());
         if (wq_entry && !wq_entry->inService) {
             DPRINTF(Cache, "Potential to merge writeback %s", pkt->print());
         }

         writeBuffer.allocate(blk_addr, blkSize, pkt, time, order++);

         if (writeBuffer.isFull()) {
             setBlocked((BlockedCause)MSHRQueue_WriteBuffer);
         }

         // schedule the send
         schedMemSideSendEvent(time);
     }

     /**
      * Returns true if the cache is blocked for accesses.
      */
     bool isBlocked() const
     {
         return blocked != 0;
     }

     /**
      * Marks the access path of the cache as blocked for the given cause. This
      * also sets the blocked flag in the slave interface.
      * @param cause The reason for the cache blocking.
      */
     void setBlocked(BlockedCause cause)
     {
         uint8_t flag = 1 << cause;
         if (blocked == 0) {
             blocked_causes[cause]++;
             blockedCycle = curCycle();
             cpuSidePort->setBlocked();
         }
         blocked |= flag;
         DPRINTF(Cache,"Blocking for cause %d, mask=%d\n", cause, blocked);
     }

     /**
      * Marks the cache as unblocked for the given cause. This also clears the
      * blocked flags in the appropriate interfaces.
      * @param cause The newly unblocked cause.
      * @warning Calling this function can cause a blocked request on the bus to
      * access the cache. The cache must be in a state to handle that request.
      */
     void clearBlocked(BlockedCause cause)
     {
         uint8_t flag = 1 << cause;
         blocked &= ~flag;
         DPRINTF(Cache,"Unblocking for cause %d, mask=%d\n", cause, blocked);
         if (blocked == 0) {
             blocked_cycles[cause] += curCycle() - blockedCycle;
             cpuSidePort->clearBlocked();
         }
     }

     /**
      * Schedule a send event for the memory-side port. If already
      * scheduled, this may reschedule the event at an earlier
      * time. When the specified time is reached, the port is free to
      * send either a response, a request, or a prefetch request.
      *
      * @param time The time when to attempt sending a packet.
      */
     void schedMemSideSendEvent(Tick time)
     {
         memSidePort->schedSendEvent(time);
     }

     virtual bool inCache(Addr addr, bool is_secure) const = 0;

     virtual bool inMissQueue(Addr addr, bool is_secure) const = 0;

     void incMissCount(PacketPtr pkt)
     {
         assert(pkt->req->masterId() < system->maxMasters());
         misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
         pkt->req->incAccessDepth();
         if (missCount) {
             --missCount;
             if (missCount == 0)
                 exitSimLoop("A cache reached the maximum miss count");
         }
     }
     void incHitCount(PacketPtr pkt)
     {
         assert(pkt->req->masterId() < system->maxMasters());
         hits[pkt->cmdToIndex()][pkt->req->masterId()]++;

     }

 };

 #endif //__MEM_CACHE_BASE_HH__
	/*
	* Copyright (c) 2012-2013, 2015-2016 ARM Limited
	* All rights reserved.
	*
	* The license below extends only to copyright in the software and shall
	* not be construed as granting a license to any other intellectual
	* property including but not limited to intellectual property relating
	* to a hardware implementation of the functionality of the software
	* licensed hereunder. You may use the software subject to the license
	* terms below provided that you ensure that this notice is replicated
	* unmodified and in its entirety in all distributions of the software,
	* modified or unmodified, in source code or in binary form.
	*
	* Copyright (c) 2003-2005 The Regents of The University of Michigan
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are
	* met: redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer;
	* redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution;
	* neither the name of the copyright holders nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*
	* Authors: Erik Hallnor
	* Steve Reinhardt
	* Ron Dreslinski
	*/

	/**
	* @file
	* Declares a basic cache interface BaseCache.
	*/

	#ifndef __MEM_CACHE_BASE_HH__
	#define __MEM_CACHE_BASE_HH__

	#include <algorithm>
	#include <list>
	#include <string>
	#include <vector>

	#include "base/misc.hh"
	#include "base/statistics.hh"
	#include "base/trace.hh"
	#include "base/types.hh"
	#include "debug/Cache.hh"
	#include "debug/CachePort.hh"
	#include "mem/cache/mshr_queue.hh"
	#include "mem/cache/write_queue.hh"
	#include "mem/mem_object.hh"
	#include "mem/packet.hh"
	#include "mem/qport.hh"
	#include "mem/request.hh"
	#include "params/BaseCache.hh"
	#include "sim/eventq.hh"
	#include "sim/full_system.hh"
	#include "sim/sim_exit.hh"
	#include "sim/system.hh"

	/**
	* A basic cache interface. Implements some common functions for speed.
	*/
	class BaseCache : public MemObject
	{
	protected:
	/**
	* Indexes to enumerate the MSHR queues.
	*/
	enum MSHRQueueIndex {
	MSHRQueue_MSHRs,
	MSHRQueue_WriteBuffer
	};

	public:
	/**
	* Reasons for caches to be blocked.
	*/
	enum BlockedCause {
	Blocked_NoMSHRs = MSHRQueue_MSHRs,
	Blocked_NoWBBuffers = MSHRQueue_WriteBuffer,
	Blocked_NoTargets,
	NUM_BLOCKED_CAUSES
	};

	protected:

	/**
	* A cache master port is used for the memory-side port of the
	* cache, and in addition to the basic timing port that only sends
	* response packets through a transmit list, it also offers the
	* ability to schedule and send request packets (requests &
	* writebacks). The send event is scheduled through schedSendEvent,
	* and the sendDeferredPacket of the timing port is modified to
	* consider both the transmit list and the requests from the MSHR.
	*/
	class CacheMasterPort : public QueuedMasterPort
	{

	public:

	/**
	* Schedule a send of a request packet (from the MSHR). Note
	* that we could already have a retry outstanding.
	*/
	void schedSendEvent(Tick time)
	{
	DPRINTF(CachePort, "Scheduling send event at %llu\n", time);
	reqQueue.schedSendEvent(time);
	}

	protected:

	CacheMasterPort(const std::string &_name, BaseCache *_cache,
	ReqPacketQueue &_reqQueue,
	SnoopRespPacketQueue &_snoopRespQueue) :
	QueuedMasterPort(_name, _cache, _reqQueue, _snoopRespQueue)
	{ }

	/**
	* Memory-side port always snoops.
	*
	* @return always true
	*/
	virtual bool isSnooping() const { return true; }
	};

	/**
	* A cache slave port is used for the CPU-side port of the cache,
	* and it is basically a simple timing port that uses a transmit
	* list for responses to the CPU (or connected master). In
	* addition, it has the functionality to block the port for
	* incoming requests. If blocked, the port will issue a retry once
	* unblocked.
	*/
	class CacheSlavePort : public QueuedSlavePort
	{

	public:

	/** Do not accept any new requests. */
	void setBlocked();

	/** Return to normal operation and accept new requests. */
	void clearBlocked();

	bool isBlocked() const { return blocked; }

	protected:

	CacheSlavePort(const std::string &_name, BaseCache *_cache,
	const std::string &_label);

	/** A normal packet queue used to store responses. */
	RespPacketQueue queue;

	bool blocked;

	bool mustSendRetry;

	private:

	void processSendRetry();

	EventFunctionWrapper sendRetryEvent;

	};

	CacheSlavePort *cpuSidePort;
	CacheMasterPort *memSidePort;

	protected:

	/** Miss status registers */
	MSHRQueue mshrQueue;

	/** Write/writeback buffer */
	WriteQueue writeBuffer;

	/**
	* Mark a request as in service (sent downstream in the memory
	* system), effectively making this MSHR the ordering point.
	*/
	void markInService(MSHR *mshr, bool pending_modified_resp)
	{
	bool wasFull = mshrQueue.isFull();
	mshrQueue.markInService(mshr, pending_modified_resp);

	if (wasFull && !mshrQueue.isFull()) {
	clearBlocked(Blocked_NoMSHRs);
	}
	}

	void markInService(WriteQueueEntry *entry)
	{
	bool wasFull = writeBuffer.isFull();
	writeBuffer.markInService(entry);

	if (wasFull && !writeBuffer.isFull()) {
	clearBlocked(Blocked_NoWBBuffers);
	}
	}

	/**
	* Determine if we should allocate on a fill or not.
	*
	* @param cmd Packet command being added as an MSHR target
	*
	* @return Whether we should allocate on a fill or not
	*/
	virtual bool allocOnFill(MemCmd cmd) const = 0;

	/**
	* Write back dirty blocks in the cache using functional accesses.
	*/
	virtual void memWriteback() override = 0;
	/**
	* Invalidates all blocks in the cache.
	*
	* @warn Dirty cache lines will not be written back to
	* memory. Make sure to call functionalWriteback() first if you
	* want the to write them to memory.
	*/
	virtual void memInvalidate() override = 0;
	/**
	* Determine if there are any dirty blocks in the cache.
	*
	* \return true if at least one block is dirty, false otherwise.
	*/
	virtual bool isDirty() const = 0;

	/**
	* Determine if an address is in the ranges covered by this
	* cache. This is useful to filter snoops.
	*
	* @param addr Address to check against
	*
	* @return If the address in question is in range
	*/
	bool inRange(Addr addr) const;

	/** Block size of this cache */
	const unsigned blkSize;

	/**
	* The latency of tag lookup of a cache. It occurs when there is
	* an access to the cache.
	*/
	const Cycles lookupLatency;

	/**
	* The latency of data access of a cache. It occurs when there is
	* an access to the cache.
	*/
	const Cycles dataLatency;

	/**
	* This is the forward latency of the cache. It occurs when there
	* is a cache miss and a request is forwarded downstream, in
	* particular an outbound miss.
	*/
	const Cycles forwardLatency;

	/** The latency to fill a cache block */
	const Cycles fillLatency;

	/**
	* The latency of sending reponse to its upper level cache/core on
	* a linefill. The responseLatency parameter captures this
	* latency.
	*/
	const Cycles responseLatency;

	/** The number of targets for each MSHR. */
	const int numTarget;

	/** Do we forward snoops from mem side port through to cpu side port? */
	bool forwardSnoops;

	/**
	* Is this cache read only, for example the instruction cache, or
	* table-walker cache. A cache that is read only should never see
	* any writes, and should never get any dirty data (and hence
	* never have to do any writebacks).
	*/
	const bool isReadOnly;

	/**
	* Bit vector of the blocking reasons for the access path.
	* @sa #BlockedCause
	*/
	uint8_t blocked;

	/** Increasing order number assigned to each incoming request. */
	uint64_t order;

	/** Stores time the cache blocked for statistics. */
	Cycles blockedCycle;

	/** Pointer to the MSHR that has no targets. */
	MSHR *noTargetMSHR;

	/** The number of misses to trigger an exit event. */
	Counter missCount;

	/**
	* The address range to which the cache responds on the CPU side.
	* Normally this is all possible memory addresses. */
	const AddrRangeList addrRanges;

	public:
	/** System we are currently operating in. */
	System *system;

	// Statistics
	/**
	* @addtogroup CacheStatistics
	* @{
	*/

	/** Number of hits per thread for each type of command.
	@sa Packet::Command */
	Stats::Vector hits[MemCmd::NUM_MEM_CMDS];
	/** Number of hits for demand accesses. */
	Stats::Formula demandHits;
	/** Number of hit for all accesses. */
	Stats::Formula overallHits;

	/** Number of misses per thread for each type of command.
	@sa Packet::Command */
	Stats::Vector misses[MemCmd::NUM_MEM_CMDS];
	/** Number of misses for demand accesses. */
	Stats::Formula demandMisses;
	/** Number of misses for all accesses. */
	Stats::Formula overallMisses;

	/**
	* Total number of cycles per thread/command spent waiting for a miss.
	* Used to calculate the average miss latency.
	*/
	Stats::Vector missLatency[MemCmd::NUM_MEM_CMDS];
	/** Total number of cycles spent waiting for demand misses. */
	Stats::Formula demandMissLatency;
	/** Total number of cycles spent waiting for all misses. */
	Stats::Formula overallMissLatency;

	/** The number of accesses per command and thread. */
	Stats::Formula accesses[MemCmd::NUM_MEM_CMDS];
	/** The number of demand accesses. */
	Stats::Formula demandAccesses;
	/** The number of overall accesses. */
	Stats::Formula overallAccesses;

	/** The miss rate per command and thread. */
	Stats::Formula missRate[MemCmd::NUM_MEM_CMDS];
	/** The miss rate of all demand accesses. */
	Stats::Formula demandMissRate;
	/** The miss rate for all accesses. */
	Stats::Formula overallMissRate;

	/** The average miss latency per command and thread. */
	Stats::Formula avgMissLatency[MemCmd::NUM_MEM_CMDS];
	/** The average miss latency for demand misses. */
	Stats::Formula demandAvgMissLatency;
	/** The average miss latency for all misses. */
	Stats::Formula overallAvgMissLatency;

	/** The total number of cycles blocked for each blocked cause. */
	Stats::Vector blocked_cycles;
	/** The number of times this cache blocked for each blocked cause. */
	Stats::Vector blocked_causes;

	/** The average number of cycles blocked for each blocked cause. */
	Stats::Formula avg_blocked;

	/** The number of times a HW-prefetched block is evicted w/o reference. */
	Stats::Scalar unusedPrefetches;

	/** Number of blocks written back per thread. */
	Stats::Vector writebacks;

	/** Number of misses that hit in the MSHRs per command and thread. */
	Stats::Vector mshr_hits[MemCmd::NUM_MEM_CMDS];
	/** Demand misses that hit in the MSHRs. */
	Stats::Formula demandMshrHits;
	/** Total number of misses that hit in the MSHRs. */
	Stats::Formula overallMshrHits;

	/** Number of misses that miss in the MSHRs, per command and thread. */
	Stats::Vector mshr_misses[MemCmd::NUM_MEM_CMDS];
	/** Demand misses that miss in the MSHRs. */
	Stats::Formula demandMshrMisses;
	/** Total number of misses that miss in the MSHRs. */
	Stats::Formula overallMshrMisses;

	/** Number of misses that miss in the MSHRs, per command and thread. */
	Stats::Vector mshr_uncacheable[MemCmd::NUM_MEM_CMDS];
	/** Total number of misses that miss in the MSHRs. */
	Stats::Formula overallMshrUncacheable;

	/** Total cycle latency of each MSHR miss, per command and thread. */
	Stats::Vector mshr_miss_latency[MemCmd::NUM_MEM_CMDS];
	/** Total cycle latency of demand MSHR misses. */
	Stats::Formula demandMshrMissLatency;
	/** Total cycle latency of overall MSHR misses. */
	Stats::Formula overallMshrMissLatency;

	/** Total cycle latency of each MSHR miss, per command and thread. */
	Stats::Vector mshr_uncacheable_lat[MemCmd::NUM_MEM_CMDS];
	/** Total cycle latency of overall MSHR misses. */
	Stats::Formula overallMshrUncacheableLatency;

	#if 0
	/** The total number of MSHR accesses per command and thread. */
	Stats::Formula mshrAccesses[MemCmd::NUM_MEM_CMDS];
	/** The total number of demand MSHR accesses. */
	Stats::Formula demandMshrAccesses;
	/** The total number of MSHR accesses. */
	Stats::Formula overallMshrAccesses;
	#endif

	/** The miss rate in the MSHRs pre command and thread. */
	Stats::Formula mshrMissRate[MemCmd::NUM_MEM_CMDS];
	/** The demand miss rate in the MSHRs. */
	Stats::Formula demandMshrMissRate;
	/** The overall miss rate in the MSHRs. */
	Stats::Formula overallMshrMissRate;

	/** The average latency of an MSHR miss, per command and thread. */
	Stats::Formula avgMshrMissLatency[MemCmd::NUM_MEM_CMDS];
	/** The average latency of a demand MSHR miss. */
	Stats::Formula demandAvgMshrMissLatency;
	/** The average overall latency of an MSHR miss. */
	Stats::Formula overallAvgMshrMissLatency;

	/** The average latency of an MSHR miss, per command and thread. */
	Stats::Formula avgMshrUncacheableLatency[MemCmd::NUM_MEM_CMDS];
	/** The average overall latency of an MSHR miss. */
	Stats::Formula overallAvgMshrUncacheableLatency;

	/**
	* @}
	*/

	/**
	* Register stats for this object.
	*/
	virtual void regStats() override;

	public:
	BaseCache(const BaseCacheParams *p, unsigned blk_size);
	~BaseCache() {}

	virtual void init() override;

	virtual BaseMasterPort &getMasterPort(const std::string &if_name,
	PortID idx = InvalidPortID) override;
	virtual BaseSlavePort &getSlavePort(const std::string &if_name,
	PortID idx = InvalidPortID) override;

	/**
	* Query block size of a cache.
	* @return The block size
	*/
	unsigned
	getBlockSize() const
	{
	return blkSize;
	}

	const AddrRangeList &getAddrRanges() const { return addrRanges; }

	MSHR *allocateMissBuffer(PacketPtr pkt, Tick time, bool sched_send = true)
	{
	MSHR *mshr = mshrQueue.allocate(pkt->getBlockAddr(blkSize), blkSize,
	pkt, time, order++,
	allocOnFill(pkt->cmd));

	if (mshrQueue.isFull()) {
	setBlocked((BlockedCause)MSHRQueue_MSHRs);
	}

	if (sched_send) {
	// schedule the send
	schedMemSideSendEvent(time);
	}

	return mshr;
	}

	void allocateWriteBuffer(PacketPtr pkt, Tick time)
	{
	// should only see writes or clean evicts here
	assert(pkt->isWrite() \|\| pkt->cmd == MemCmd::CleanEvict);

	Addr blk_addr = pkt->getBlockAddr(blkSize);

	WriteQueueEntry *wq_entry =
	writeBuffer.findMatch(blk_addr, pkt->isSecure());
	if (wq_entry && !wq_entry->inService) {
	DPRINTF(Cache, "Potential to merge writeback %s", pkt->print());
	}

	writeBuffer.allocate(blk_addr, blkSize, pkt, time, order++);

	if (writeBuffer.isFull()) {
	setBlocked((BlockedCause)MSHRQueue_WriteBuffer);
	}

	// schedule the send
	schedMemSideSendEvent(time);
	}

	/**
	* Returns true if the cache is blocked for accesses.
	*/
	bool isBlocked() const
	{
	return blocked != 0;
	}

	/**
	* Marks the access path of the cache as blocked for the given cause. This
	* also sets the blocked flag in the slave interface.
	* @param cause The reason for the cache blocking.
	*/
	void setBlocked(BlockedCause cause)
	{
	uint8_t flag = 1 << cause;
	if (blocked == 0) {
	blocked_causes[cause]++;
	blockedCycle = curCycle();
	cpuSidePort->setBlocked();
	}
	blocked \|= flag;
	DPRINTF(Cache,"Blocking for cause %d, mask=%d\n", cause, blocked);
	}

	/**
	* Marks the cache as unblocked for the given cause. This also clears the
	* blocked flags in the appropriate interfaces.
	* @param cause The newly unblocked cause.
	* @warning Calling this function can cause a blocked request on the bus to
	* access the cache. The cache must be in a state to handle that request.
	*/
	void clearBlocked(BlockedCause cause)
	{
	uint8_t flag = 1 << cause;
	blocked &= ~flag;
	DPRINTF(Cache,"Unblocking for cause %d, mask=%d\n", cause, blocked);
	if (blocked == 0) {
	blocked_cycles[cause] += curCycle() - blockedCycle;
	cpuSidePort->clearBlocked();
	}
	}

	/**
	* Schedule a send event for the memory-side port. If already
	* scheduled, this may reschedule the event at an earlier
	* time. When the specified time is reached, the port is free to
	* send either a response, a request, or a prefetch request.
	*
	* @param time The time when to attempt sending a packet.
	*/
	void schedMemSideSendEvent(Tick time)
	{
	memSidePort->schedSendEvent(time);
	}

	virtual bool inCache(Addr addr, bool is_secure) const = 0;

	virtual bool inMissQueue(Addr addr, bool is_secure) const = 0;

	void incMissCount(PacketPtr pkt)
	{
	assert(pkt->req->masterId() < system->maxMasters());
	misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
	pkt->req->incAccessDepth();
	if (missCount) {
	--missCount;
	if (missCount == 0)
	exitSimLoop("A cache reached the maximum miss count");
	}
	}
	void incHitCount(PacketPtr pkt)
	{
	assert(pkt->req->masterId() < system->maxMasters());
	hits[pkt->cmdToIndex()][pkt->req->masterId()]++;

	}

	};

	#endif //__MEM_CACHE_BASE_HH__