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28 * Authors: Erik Hallnor
33 * Miss Status and Handling Register (MSHR) declaration.
41 #include "base/printable.hh"
42 #include "mem/packet.hh"
48 * Miss Status and handling Register. This class keeps all the information
49 * needed to handle a cache miss including a list of target requests.
50 * @sa \ref gem5MemorySystem "gem5 Memory System"
52 class MSHR : public Packet::SenderState, public Printable
66 Tick recvTime; //!< Time when request was received (for stats)
67 Tick readyTime; //!< Time when request is ready to be serviced
68 Counter order; //!< Global order (for memory consistency mgmt)
69 PacketPtr pkt; //!< Pending request packet.
70 Source source; //!< Did request come from cpu, memory, or prefetcher?
71 bool markedPending; //!< Did we mark upstream MSHR
72 //!< as downstreamPending?
74 Target(PacketPtr _pkt, Tick _readyTime, Counter _order,
75 Source _source, bool _markedPending)
76 : recvTime(curTick()), readyTime(_readyTime), order(_order),
77 pkt(_pkt), source(_source), markedPending(_markedPending)
81 class TargetList : public std::list<Target> {
82 /** Target list iterator. */
83 typedef std::list<Target>::iterator Iterator;
84 typedef std::list<Target>::const_iterator ConstIterator;
91 void resetFlags() { needsExclusive = hasUpgrade = false; }
92 bool isReset() { return !needsExclusive && !hasUpgrade; }
93 void add(PacketPtr pkt, Tick readyTime, Counter order,
94 Target::Source source, bool markPending);
95 void replaceUpgrades();
96 void clearDownstreamPending();
97 bool checkFunctional(PacketPtr pkt);
98 void print(std::ostream &os, int verbosity,
99 const std::string &prefix) const;
102 /** A list of MSHRs. */
103 typedef std::list<MSHR *> List;
104 /** MSHR list iterator. */
105 typedef List::iterator Iterator;
106 /** MSHR list const_iterator. */
107 typedef List::const_iterator ConstIterator;
109 /** Pointer to queue containing this MSHR. */
112 /** Cycle when ready to issue */
115 /** Order number assigned by the miss queue. */
118 /** Address of the request. */
121 /** Size of the request. */
124 /** True if the request has been sent to the bus. */
127 /** True if the request is just a simple forward from an upper level */
130 /** True if we need to get an exclusive copy of the block. */
131 bool needsExclusive() const { return targets->needsExclusive; }
133 /** True if the request is uncacheable */
136 bool downstreamPending;
138 /** The pending* and post* flags are only valid if inService is
139 * true. Using the accessor functions lets us detect if these
140 * flags are accessed improperly.
143 /** Will we have a dirty copy after this request? */
145 bool isPendingDirty() const {
146 assert(inService); return pendingDirty;
149 /** Did we snoop an invalidate while waiting for data? */
151 bool hasPostInvalidate() const {
152 assert(inService); return postInvalidate;
155 /** Did we snoop a read while waiting for data? */
157 bool hasPostDowngrade() const {
158 assert(inService); return postDowngrade;
161 /** Thread number of the miss. */
163 /** The number of currently allocated targets. */
164 unsigned short ntargets;
167 /** Data buffer (if needed). Currently used only for pending
168 * upgrade handling. */
172 * Pointer to this MSHR on the ready list.
173 * @sa MissQueue, MSHRQueue::readyList
178 * Pointer to this MSHR on the allocated list.
179 * @sa MissQueue, MSHRQueue::allocatedList
184 /** List of all requests that match the address */
187 TargetList *deferredTargets;
191 bool isUncacheable() { return _isUncacheable; }
194 * Allocate a miss to this MSHR.
195 * @param cmd The requesting command.
196 * @param addr The address of the miss.
197 * @param asid The address space id of the miss.
198 * @param size The number of bytes to request.
199 * @param pkt The original miss.
201 void allocate(Addr addr, int size, PacketPtr pkt,
202 Tick when, Counter _order);
204 bool markInService(PacketPtr pkt);
206 void clearDownstreamPending();
209 * Mark this MSHR as free.
214 * Add a request to the list of targets.
215 * @param target The target.
217 void allocateTarget(PacketPtr target, Tick when, Counter order);
218 bool handleSnoop(PacketPtr target, Counter order);
220 /** A simple constructor. */
222 /** A simple destructor. */
226 * Returns the current number of allocated targets.
227 * @return The current number of allocated targets.
229 int getNumTargets() const { return ntargets; }
232 * Returns a pointer to the target list.
233 * @return a pointer to the target list.
235 TargetList *getTargetList() { return targets; }
238 * Returns true if there are targets left.
239 * @return true if there are targets
241 bool hasTargets() const { return !targets->empty(); }
244 * Returns a reference to the first target.
245 * @return A pointer to the first target.
247 Target *getTarget() const
249 assert(hasTargets());
250 return &targets->front();
259 targets->pop_front();
262 bool isForwardNoResponse() const
264 if (getNumTargets() != 1)
266 Target *tgt = getTarget();
267 return tgt->source == Target::FromCPU && !tgt->pkt->needsResponse();
270 bool promoteDeferredTargets();
272 void handleFill(Packet *pkt, CacheBlk *blk);
274 bool checkFunctional(PacketPtr pkt);
277 * Prints the contents of this MSHR for debugging.
279 void print(std::ostream &os,
281 const std::string &prefix = "") const;