diff options
Diffstat (limited to 'src/mem/packet.hh')
| -rw-r--r-- | src/mem/packet.hh | 156 |
1 files changed, 95 insertions, 61 deletions
diff --git a/src/mem/packet.hh b/src/mem/packet.hh index 83f52ede5..e09ef4b85 100644 --- a/src/mem/packet.hh +++ b/src/mem/packet.hh @@ -28,8 +28,7 @@ /** * @file - * Declaration of the Packet Class, a packet is a transaction occuring - * between a single level of the memory heirarchy (ie L1->L2). + * Declaration of the Packet class. */ #ifndef __MEM_PACKET_HH__ @@ -44,81 +43,98 @@ typedef Packet* PacketPtr; typedef uint8_t* PacketDataPtr; /** - * A Packet is the structure to handle requests between two levels - * of the memory system. The Request is a global object that trancends - * all of the memory heirarchy, but at each levels interface a packet - * is created to transfer data/requests. For example, a request would - * be used to initiate a request to go to memory/IOdevices, as the request - * passes through the memory system several packets will be created. One - * will be created to go between the L1 and L2 caches and another to go to - * the next level and so forth. - * - * Packets are assumed to be returned in the case of a single response. If - * the transaction has no response, then the consumer will delete the packet. + * A Packet is used to encapsulate a transfer between two objects in + * the memory system (e.g., the L1 and L2 cache). (In contrast, a + * single Request travels all the way from the requester to the + * ultimate destination and back, possibly being conveyed by several + * different Packets along the way.) */ class Packet { private: - /** A pointer to the data being transfered. It can be differnt sizes - at each level of the heirarchy so it belongs in the packet, - not request. This may or may not be populated when a responder recieves - the packet. If not populated it memory should be allocated. + /** A pointer to the data being transfered. It can be differnt + * sizes at each level of the heirarchy so it belongs in the + * packet, not request. This may or may not be populated when a + * responder recieves the packet. If not populated it memory + * should be allocated. */ PacketDataPtr data; - /** Is the data pointer set to a value that shouldn't be freed when the - * packet is destroyed? */ + /** Is the data pointer set to a value that shouldn't be freed + * when the packet is destroyed? */ bool staticData; - /** The data pointer points to a value that should be freed when the packet - * is destroyed. */ + /** The data pointer points to a value that should be freed when + * the packet is destroyed. */ bool dynamicData; - /** the data pointer points to an array (thus delete [] ) needs to be called - * on it rather than simply delete.*/ + /** the data pointer points to an array (thus delete [] ) needs to + * be called on it rather than simply delete.*/ bool arrayData; - /** The address of the request, could be virtual or physical (depending on - cache configurations). */ + /** The address of the request. This address could be virtual or + * physical, depending on the system configuration. */ Addr addr; - /** Indicates the size of the request. */ + /** The size of the request or transfer. */ int size; - /** A index of the source of the transaction. */ + /** Device address (e.g., bus ID) of the source of the + * transaction. The source is not responsible for setting this + * field; it is set implicitly by the interconnect when the + * packet * is first sent. */ short src; - /** A index to the destination of the transaction. */ + /** Device address (e.g., bus ID) of the destination of the + * transaction. The special value Broadcast indicates that the + * packet should be routed based on its address. This field is + * initialized in the constructor and is thus always valid + * (unlike * addr, size, and src). */ short dest; + /** Is the 'addr' field valid? */ bool addrValid; + /** Is the 'size' field valid? */ bool sizeValid; + /** Is the 'src' field valid? */ bool srcValid; public: + /** The special destination address indicating that the packet + * should be routed based on its address. */ static const short Broadcast = -1; - /** A pointer to the overall request. */ + /** A pointer to the original request. */ RequestPtr req; + /** A virtual base opaque structure used to hold coherence-related + * state. A specific subclass would be derived from this to + * carry state specific to a particular coherence protocol. */ class CoherenceState { public: virtual ~CoherenceState() {} }; - /** A virtual base opaque structure used to hold - coherence status messages. */ - CoherenceState *coherence; // virtual base opaque, - // assert(dynamic_cast<Foo>) etc. - + /** This packet's coherence state. Caches should use + * dynamic_cast<> to cast to the state appropriate for the + * system's coherence protocol. */ + CoherenceState *coherence; + + /** A virtual base opaque structure used to hold state associated + * with the packet but specific to the sending device (e.g., an + * MSHR). A pointer to this state is returned in the packet's + * response so that the sender can quickly look up the state + * needed to process it. A specific subclass would be derived + * from this to carry state specific to a particular sending + * device. */ class SenderState { public: virtual ~SenderState() {} }; - /** A virtual base opaque structure used to hold the senders state. */ - SenderState *senderState; // virtual base opaque, - // assert(dynamic_cast<Foo>) etc. + /** This packet's sender state. Devices should use dynamic_cast<> + * to cast to the state appropriate to the sender. */ + SenderState *senderState; private: /** List of command attributes. */ @@ -144,9 +160,11 @@ class Packet WriteResp = IsWrite | IsResponse }; + /** Return the string name of the cmd field (for debugging and + * tracing). */ const std::string &cmdString() const; - /** The command of the transaction. */ + /** The command field of the packet. */ Command cmd; bool isRead() { return (cmd & IsRead) != 0; } @@ -154,20 +172,7 @@ class Packet bool isResponse() { return (cmd & IsResponse) != 0; } bool needsResponse() { return (cmd & NeedsResponse) != 0; } - void makeTimingResponse() { - assert(needsResponse()); - int icmd = (int)cmd; - icmd &= ~(IsRequest | NeedsResponse); - icmd |= IsResponse; - cmd = (Command)icmd; - dest = src; - srcValid = false; - } - - /** The time this request was responded to. Used to calculate latencies. */ - Tick time; - - /** The result of a particular packets request. */ + /** Possible results of a packet's request. */ enum Result { Success, @@ -175,7 +180,7 @@ class Packet Unknown }; - /** The result of the packet transaction. */ + /** The result of this packet's request. */ Result result; /** Accessor function that returns the source index of the packet. */ @@ -193,27 +198,56 @@ class Packet int getSize() const { assert(sizeValid); return size; } void setSize(int _size) { size = _size; sizeValid = true; } - + /** Constructor. Note that a Request object must be constructed + * first, but the Requests's physical address and size fields + * need not be valid. The command and destination addresses + * must be supplied. */ Packet(Request *_req, Command _cmd, short _dest) : data(NULL), staticData(false), dynamicData(false), arrayData(false), addr(_req->paddr), size(_req->size), dest(_dest), addrValid(_req->validPaddr), sizeValid(_req->validSize), srcValid(false), req(_req), coherence(NULL), senderState(NULL), cmd(_cmd), - time(curTick), result(Unknown) + result(Unknown) { } + /** Destructor. */ ~Packet() { deleteData(); } - - /** Minimally reset a packet so something like simple cpu can reuse it. */ - void reset(); - + /** Reinitialize packet address and size from the associated + * Request object, and reset other fields that may have been + * modified by a previous transaction. Typically called when a + * statically allocated Request/Packet pair is reused for + * multiple transactions. */ void reinitFromRequest() { - if (req->validPaddr) setAddr(req->paddr); - if (req->validSize) setSize(req->size); + assert(req->validPaddr); + setAddr(req->paddr); + assert(req->validSize); + setSize(req->size); + result = Unknown; + if (dynamicData) { + deleteData(); + dynamicData = false; + arrayData = false; + } + } + + /** Take a request packet and modify it in place to be suitable + * for returning as a response to that request. Used for timing + * accesses only. For atomic and functional accesses, the + * request packet is always implicitly passed back *without* + * modifying the command or destination fields, so this function + * should not be called. */ + void makeTimingResponse() { + assert(needsResponse()); + int icmd = (int)cmd; + icmd &= ~(IsRequest | NeedsResponse); + icmd |= IsResponse; + cmd = (Command)icmd; + dest = src; + srcValid = false; } /** Set the data pointer to the following value that should not be freed. */ |