src/mem/cache/mshr.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) 2002-2005 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
  */

 /**
  * @file
  * Miss Status and Handling Register (MSHR) declaration.
  */

 #ifndef __MEM_CACHE_MSHR_HH__
 #define __MEM_CACHE_MSHR_HH__

 #include <list>

 #include "base/printable.hh"
 #include "mem/cache/queue_entry.hh"

 class Cache;

 /**
  * Miss Status and handling Register. This class keeps all the information
  * needed to handle a cache miss including a list of target requests.
  * @sa  \ref gem5MemorySystem "gem5 Memory System"
  */
 class MSHR : public QueueEntry, public Printable
 {

     /**
      * Consider the queues friends to avoid making everything public.
      */
     template<typename Entry>
     friend class Queue;
     friend class MSHRQueue;

   private:

     /** Flag set by downstream caches */
     bool downstreamPending;

     /**
      * Here we use one flag to track both if:
      *
      * 1. We are going to become owner or not, i.e., we will get the
      * block in an ownership state (Owned or Modified) with BlkDirty
      * set. This determines whether or not we are going to become the
      * responder and ordering point for future requests that we snoop.
      *
      * 2. We know that we are going to get a writable block, i.e. we
      * will get the block in writable state (Exclusive or Modified
      * state) with BlkWritable set. That determines whether additional
      * targets with needsWritable set will be able to be satisfied, or
      * if not should be put on the deferred list to possibly wait for
      * another request that does give us writable access.
      *
      * Condition 2 is actually just a shortcut that saves us from
      * possibly building a deferred target list and calling
      * promoteWritable() every time we get a writable block. Condition
      * 1, tracking ownership, is what is important. However, we never
      * receive ownership without marking the block dirty, and
      * consequently use pendingModified to track both ownership and
      * writability rather than having separate pendingDirty and
      * pendingWritable flags.
      */
     bool pendingModified;

     /** Did we snoop an invalidate while waiting for data? */
     bool postInvalidate;

     /** Did we snoop a read while waiting for data? */
     bool postDowngrade;

   public:

     /** True if the entry is just a simple forward from an upper level */
     bool isForward;

     class Target {
       public:

         enum Source {
             FromCPU,
             FromSnoop,
             FromPrefetcher
         };

         const Tick recvTime;  //!< Time when request was received (for stats)
         const Tick readyTime; //!< Time when request is ready to be serviced
         const Counter order;  //!< Global order (for memory consistency mgmt)
         const PacketPtr pkt;  //!< Pending request packet.
         const Source source;  //!< Request from cpu, memory, or prefetcher?

         /**
          * We use this flag to track whether we have cleared the
          * downstreamPending flag for the MSHR of the cache above
          * where this packet originates from and guard noninitial
          * attempts to clear it.
          *
          * The flag markedPending needs to be updated when the
          * TargetList is in service which can be:
          * 1) during the Target instantiation if the MSHR is in
          * service and the target is not deferred,
          * 2) when the MSHR becomes in service if the target is not
          * deferred,
          * 3) or when the TargetList is promoted (deferredTargets ->
          * targets).
          */
         bool markedPending;

         const bool allocOnFill;   //!< Should the response servicing this
                                   //!< target list allocate in the cache?

         Target(PacketPtr _pkt, Tick _readyTime, Counter _order,
                Source _source, bool _markedPending, bool alloc_on_fill)
             : recvTime(curTick()), readyTime(_readyTime), order(_order),
               pkt(_pkt), source(_source), markedPending(_markedPending),
               allocOnFill(alloc_on_fill)
         {}
     };

     class TargetList : public std::list<Target> {

       public:
         bool needsWritable;
         bool hasUpgrade;
         /** Set when the response should allocate on fill */
         bool allocOnFill;

         TargetList();

         /**
          * Use the provided packet and the source to update the
          * flags of this TargetList.
          *
          * @param pkt Packet considered for the flag update
          * @param source Indicates the source of the packet
          * @param alloc_on_fill Whether the pkt would allocate on a fill
          */
         void updateFlags(PacketPtr pkt, Target::Source source,
                          bool alloc_on_fill);

         void resetFlags() { needsWritable = hasUpgrade = allocOnFill = false; }

         /**
          * Goes through the list of targets and uses them to populate
          * the flags of this TargetList. When the function returns the
          * flags are consistent with the properties of packets in the
          * list.
          */
         void populateFlags();

         /**
          * Tests if the flags of this TargetList have their default
          * values.
          */
         bool isReset() const {
             return !needsWritable && !hasUpgrade && !allocOnFill;
         }

         /**
          * Add the specified packet in the TargetList. This function
          * stores information related to the added packet and updates
          * accordingly the flags.
          *
          * @param pkt Packet considered for adding
          * @param readTime Tick at which the packet is processed by this cache
          * @param order A counter giving a unique id to each target
          * @param source Indicates the source agent of the packet
          * @param markPending Set for deferred targets or pending MSHRs
          * @param alloc_on_fill Whether it should allocate on a fill
          */
         void add(PacketPtr pkt, Tick readyTime, Counter order,
                  Target::Source source, bool markPending,
                  bool alloc_on_fill);

         /**
          * Convert upgrades to the equivalent request if the cache line they
          * refer to would have been invalid (Upgrade -> ReadEx, SC* -> Fail).
          * Used to rejig ordering between targets waiting on an MSHR. */
         void replaceUpgrades();

         void clearDownstreamPending();
         bool checkFunctional(PacketPtr pkt);
         void print(std::ostream &os, int verbosity,
                    const std::string &prefix) const;
     };

     /** A list of MSHRs. */
     typedef std::list<MSHR *> List;
     /** MSHR list iterator. */
     typedef List::iterator Iterator;

     /** The pending* and post* flags are only valid if inService is
      *  true.  Using the accessor functions lets us detect if these
      *  flags are accessed improperly.
      */

     /** True if we need to get a writable copy of the block. */
     bool needsWritable() const { return targets.needsWritable; }

     bool isPendingModified() const {
         assert(inService); return pendingModified;
     }

     bool hasPostInvalidate() const {
         assert(inService); return postInvalidate;
     }

     bool hasPostDowngrade() const {
         assert(inService); return postDowngrade;
     }

     bool sendPacket(Cache &cache);

     bool allocOnFill() const {
         return targets.allocOnFill;
     }
   private:

     /**
      * Pointer to this MSHR on the ready list.
      * @sa MissQueue, MSHRQueue::readyList
      */
     Iterator readyIter;

     /**
      * Pointer to this MSHR on the allocated list.
      * @sa MissQueue, MSHRQueue::allocatedList
      */
     Iterator allocIter;

     /** List of all requests that match the address */
     TargetList targets;

     TargetList deferredTargets;

   public:

     /**
      * Allocate a miss to this MSHR.
      * @param blk_addr The address of the block.
      * @param blk_size The number of bytes to request.
      * @param pkt The original miss.
      * @param when_ready When should the MSHR be ready to act upon.
      * @param _order The logical order of this MSHR
      * @param alloc_on_fill Should the cache allocate a block on fill
      */
     void allocate(Addr blk_addr, unsigned blk_size, PacketPtr pkt,
                   Tick when_ready, Counter _order, bool alloc_on_fill);

     void markInService(bool pending_modified_resp);

     void clearDownstreamPending();

     /**
      * Mark this MSHR as free.
      */
     void deallocate();

     /**
      * Add a request to the list of targets.
      * @param target The target.
      */
     void allocateTarget(PacketPtr target, Tick when, Counter order,
                         bool alloc_on_fill);
     bool handleSnoop(PacketPtr target, Counter order);

     /** A simple constructor. */
     MSHR();

     /**
      * Returns the current number of allocated targets.
      * @return The current number of allocated targets.
      */
     int getNumTargets() const
     { return targets.size() + deferredTargets.size(); }

     /**
      * Extracts the subset of the targets that can be serviced given a
      * received response. This function returns the targets list
      * unless the response is a ReadRespWithInvalidate. The
      * ReadRespWithInvalidate is only invalidating response that its
      * invalidation was not expected when the request (a
      * ReadSharedReq) was sent out. For ReadRespWithInvalidate we can
      * safely service only the first FromCPU target and all FromSnoop
      * targets (inform all snoopers that we no longer have the block).
      *
      * @param pkt The response from the downstream memory
      */
     TargetList extractServiceableTargets(PacketPtr pkt);

     /**
      * Returns true if there are targets left.
      * @return true if there are targets
      */
     bool hasTargets() const { return !targets.empty(); }

     /**
      * Returns a reference to the first target.
      * @return A pointer to the first target.
      */
     Target *getTarget()
     {
         assert(hasTargets());
         return &targets.front();
     }

     /**
      * Pop first target.
      */
     void popTarget()
     {
         targets.pop_front();
     }

     bool promoteDeferredTargets();

     void promoteWritable();

     bool checkFunctional(PacketPtr pkt);

     /**
      * Prints the contents of this MSHR for debugging.
      */
     void print(std::ostream &os,
                int verbosity = 0,
                const std::string &prefix = "") const;
     /**
      * A no-args wrapper of print(std::ostream...)  meant to be
      * invoked from DPRINTFs avoiding string overheads in fast mode
      *
      * @return string with mshr fields + [deferred]targets
      */
     std::string print() const;
 };

 #endif // __MEM_CACHE_MSHR_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) 2002-2005 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
	*/

	/**
	* @file
	* Miss Status and Handling Register (MSHR) declaration.
	*/

	#ifndef __MEM_CACHE_MSHR_HH__
	#define __MEM_CACHE_MSHR_HH__

	#include <list>

	#include "base/printable.hh"
	#include "mem/cache/queue_entry.hh"

	class Cache;

	/**
	* Miss Status and handling Register. This class keeps all the information
	* needed to handle a cache miss including a list of target requests.
	* @sa \ref gem5MemorySystem "gem5 Memory System"
	*/
	class MSHR : public QueueEntry, public Printable
	{

	/**
	* Consider the queues friends to avoid making everything public.
	*/
	template<typename Entry>
	friend class Queue;
	friend class MSHRQueue;

	private:

	/** Flag set by downstream caches */
	bool downstreamPending;

	/**
	* Here we use one flag to track both if:
	*
	* 1. We are going to become owner or not, i.e., we will get the
	* block in an ownership state (Owned or Modified) with BlkDirty
	* set. This determines whether or not we are going to become the
	* responder and ordering point for future requests that we snoop.
	*
	* 2. We know that we are going to get a writable block, i.e. we
	* will get the block in writable state (Exclusive or Modified
	* state) with BlkWritable set. That determines whether additional
	* targets with needsWritable set will be able to be satisfied, or
	* if not should be put on the deferred list to possibly wait for
	* another request that does give us writable access.
	*
	* Condition 2 is actually just a shortcut that saves us from
	* possibly building a deferred target list and calling
	* promoteWritable() every time we get a writable block. Condition
	* 1, tracking ownership, is what is important. However, we never
	* receive ownership without marking the block dirty, and
	* consequently use pendingModified to track both ownership and
	* writability rather than having separate pendingDirty and
	* pendingWritable flags.
	*/
	bool pendingModified;

	/** Did we snoop an invalidate while waiting for data? */
	bool postInvalidate;

	/** Did we snoop a read while waiting for data? */
	bool postDowngrade;

	public:

	/** True if the entry is just a simple forward from an upper level */
	bool isForward;

	class Target {
	public:

	enum Source {
	FromCPU,
	FromSnoop,
	FromPrefetcher
	};

	const Tick recvTime; //!< Time when request was received (for stats)
	const Tick readyTime; //!< Time when request is ready to be serviced
	const Counter order; //!< Global order (for memory consistency mgmt)
	const PacketPtr pkt; //!< Pending request packet.
	const Source source; //!< Request from cpu, memory, or prefetcher?

	/**
	* We use this flag to track whether we have cleared the
	* downstreamPending flag for the MSHR of the cache above
	* where this packet originates from and guard noninitial
	* attempts to clear it.
	*
	* The flag markedPending needs to be updated when the
	* TargetList is in service which can be:
	* 1) during the Target instantiation if the MSHR is in
	* service and the target is not deferred,
	* 2) when the MSHR becomes in service if the target is not
	* deferred,
	* 3) or when the TargetList is promoted (deferredTargets ->
	* targets).
	*/
	bool markedPending;

	const bool allocOnFill; //!< Should the response servicing this
	//!< target list allocate in the cache?

	Target(PacketPtr _pkt, Tick _readyTime, Counter _order,
	Source _source, bool _markedPending, bool alloc_on_fill)
	: recvTime(curTick()), readyTime(_readyTime), order(_order),
	pkt(_pkt), source(_source), markedPending(_markedPending),
	allocOnFill(alloc_on_fill)
	{}
	};

	class TargetList : public std::list<Target> {

	public:
	bool needsWritable;
	bool hasUpgrade;
	/** Set when the response should allocate on fill */
	bool allocOnFill;

	TargetList();

	/**
	* Use the provided packet and the source to update the
	* flags of this TargetList.
	*
	* @param pkt Packet considered for the flag update
	* @param source Indicates the source of the packet
	* @param alloc_on_fill Whether the pkt would allocate on a fill
	*/
	void updateFlags(PacketPtr pkt, Target::Source source,
	bool alloc_on_fill);

	void resetFlags() { needsWritable = hasUpgrade = allocOnFill = false; }

	/**
	* Goes through the list of targets and uses them to populate
	* the flags of this TargetList. When the function returns the
	* flags are consistent with the properties of packets in the
	* list.
	*/
	void populateFlags();

	/**
	* Tests if the flags of this TargetList have their default
	* values.
	*/
	bool isReset() const {
	return !needsWritable && !hasUpgrade && !allocOnFill;
	}

	/**
	* Add the specified packet in the TargetList. This function
	* stores information related to the added packet and updates
	* accordingly the flags.
	*
	* @param pkt Packet considered for adding
	* @param readTime Tick at which the packet is processed by this cache
	* @param order A counter giving a unique id to each target
	* @param source Indicates the source agent of the packet
	* @param markPending Set for deferred targets or pending MSHRs
	* @param alloc_on_fill Whether it should allocate on a fill
	*/
	void add(PacketPtr pkt, Tick readyTime, Counter order,
	Target::Source source, bool markPending,
	bool alloc_on_fill);

	/**
	* Convert upgrades to the equivalent request if the cache line they
	* refer to would have been invalid (Upgrade -> ReadEx, SC* -> Fail).
	* Used to rejig ordering between targets waiting on an MSHR. */
	void replaceUpgrades();

	void clearDownstreamPending();
	bool checkFunctional(PacketPtr pkt);
	void print(std::ostream &os, int verbosity,
	const std::string &prefix) const;
	};

	/** A list of MSHRs. */
	typedef std::list<MSHR *> List;
	/** MSHR list iterator. */
	typedef List::iterator Iterator;

	/** The pending* and post* flags are only valid if inService is
	* true. Using the accessor functions lets us detect if these
	* flags are accessed improperly.
	*/

	/** True if we need to get a writable copy of the block. */
	bool needsWritable() const { return targets.needsWritable; }

	bool isPendingModified() const {
	assert(inService); return pendingModified;
	}

	bool hasPostInvalidate() const {
	assert(inService); return postInvalidate;
	}

	bool hasPostDowngrade() const {
	assert(inService); return postDowngrade;
	}

	bool sendPacket(Cache &cache);

	bool allocOnFill() const {
	return targets.allocOnFill;
	}
	private:

	/**
	* Pointer to this MSHR on the ready list.
	* @sa MissQueue, MSHRQueue::readyList
	*/
	Iterator readyIter;

	/**
	* Pointer to this MSHR on the allocated list.
	* @sa MissQueue, MSHRQueue::allocatedList
	*/
	Iterator allocIter;

	/** List of all requests that match the address */
	TargetList targets;

	TargetList deferredTargets;

	public:

	/**
	* Allocate a miss to this MSHR.
	* @param blk_addr The address of the block.
	* @param blk_size The number of bytes to request.
	* @param pkt The original miss.
	* @param when_ready When should the MSHR be ready to act upon.
	* @param _order The logical order of this MSHR
	* @param alloc_on_fill Should the cache allocate a block on fill
	*/
	void allocate(Addr blk_addr, unsigned blk_size, PacketPtr pkt,
	Tick when_ready, Counter _order, bool alloc_on_fill);

	void markInService(bool pending_modified_resp);

	void clearDownstreamPending();

	/**
	* Mark this MSHR as free.
	*/
	void deallocate();

	/**
	* Add a request to the list of targets.
	* @param target The target.
	*/
	void allocateTarget(PacketPtr target, Tick when, Counter order,
	bool alloc_on_fill);
	bool handleSnoop(PacketPtr target, Counter order);

	/** A simple constructor. */
	MSHR();

	/**
	* Returns the current number of allocated targets.
	* @return The current number of allocated targets.
	*/
	int getNumTargets() const
	{ return targets.size() + deferredTargets.size(); }

	/**
	* Extracts the subset of the targets that can be serviced given a
	* received response. This function returns the targets list
	* unless the response is a ReadRespWithInvalidate. The
	* ReadRespWithInvalidate is only invalidating response that its
	* invalidation was not expected when the request (a
	* ReadSharedReq) was sent out. For ReadRespWithInvalidate we can
	* safely service only the first FromCPU target and all FromSnoop
	* targets (inform all snoopers that we no longer have the block).
	*
	* @param pkt The response from the downstream memory
	*/
	TargetList extractServiceableTargets(PacketPtr pkt);

	/**
	* Returns true if there are targets left.
	* @return true if there are targets
	*/
	bool hasTargets() const { return !targets.empty(); }

	/**
	* Returns a reference to the first target.
	* @return A pointer to the first target.
	*/
	Target *getTarget()
	{
	assert(hasTargets());
	return &targets.front();
	}

	/**
	* Pop first target.
	*/
	void popTarget()
	{
	targets.pop_front();
	}

	bool promoteDeferredTargets();

	void promoteWritable();

	bool checkFunctional(PacketPtr pkt);

	/**
	* Prints the contents of this MSHR for debugging.
	*/
	void print(std::ostream &os,
	int verbosity = 0,
	const std::string &prefix = "") const;
	/**
	* A no-args wrapper of print(std::ostream...) meant to be
	* invoked from DPRINTFs avoiding string overheads in fast mode
	*
	* @return string with mshr fields + [deferred]targets
	*/
	std::string print() const;
	};

	#endif // __MEM_CACHE_MSHR_HH__