mshr.hh revision 6221 
1/*
2 * Copyright (c) 2002-2005 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Erik Hallnor
29 */
30
31/**
32 * @file
33 * Miss Status and Handling Register (MSHR) declaration.
34 */
35
36#ifndef __MSHR_HH__
37#define __MSHR_HH__
38
39#include <list>
40
41#include "base/printable.hh"
42#include "mem/packet.hh"
43
44class CacheBlk;
45class MSHRQueue;
46
47/**
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 */
51class MSHR : public Packet::SenderState, public Printable
52{
53
54  public:
55
56    class Target {
57      public:
58
59        enum Source {
60            FromCPU,
61            FromSnoop,
62            FromPrefetcher
63        };
64
65        Tick recvTime;  //!< Time when request was received (for stats)
66        Tick readyTime; //!< Time when request is ready to be serviced
67        Counter order;  //!< Global order (for memory consistency mgmt)
68        PacketPtr pkt;  //!< Pending request packet.
69        Source source;  //!< Did request come from cpu, memory, or prefetcher?
70        bool markedPending; //!< Did we mark upstream MSHR
71                            //!<  as downstreamPending?
72
73        Target(PacketPtr _pkt, Tick _readyTime, Counter _order,
74               Source _source, bool _markedPending)
75            : recvTime(curTick), readyTime(_readyTime), order(_order),
76              pkt(_pkt), source(_source), markedPending(_markedPending)
77        {}
78    };
79
80    class TargetList : public std::list<Target> {
81        /** Target list iterator. */
82        typedef std::list<Target>::iterator Iterator;
83        typedef std::list<Target>::const_iterator ConstIterator;
84
85      public:
86        bool needsExclusive;
87        bool hasUpgrade;
88
89        TargetList();
90        void resetFlags() { needsExclusive = hasUpgrade = false; }
91        bool isReset()    { return !needsExclusive && !hasUpgrade; }
92        void add(PacketPtr pkt, Tick readyTime, Counter order,
93                 Target::Source source, bool markPending);
94        void replaceUpgrades();
95        void clearDownstreamPending();
96        bool checkFunctional(PacketPtr pkt);
97        void print(std::ostream &os, int verbosity,
98                   const std::string &prefix) const;
99    };
100
101    /** A list of MSHRs. */
102    typedef std::list<MSHR *> List;
103    /** MSHR list iterator. */
104    typedef List::iterator Iterator;
105    /** MSHR list const_iterator. */
106    typedef List::const_iterator ConstIterator;
107
108    /** Pointer to queue containing this MSHR. */
109    MSHRQueue *queue;
110
111    /** Cycle when ready to issue */
112    Tick readyTime;
113
114    /** Order number assigned by the miss queue. */
115    Counter order;
116
117    /** Address of the request. */
118    Addr addr;
119
120    /** Size of the request. */
121    int size;
122
123    /** True if the request has been sent to the bus. */
124    bool inService;
125
126    /** True if the request is just a simple forward from an upper level */
127    bool isForward;
128
129    /** True if we need to get an exclusive copy of the block. */
130    bool needsExclusive() const { return targets->needsExclusive; }
131
132    /** True if the request is uncacheable */
133    bool _isUncacheable;
134
135    bool downstreamPending;
136
137    bool pendingInvalidate;
138    bool pendingShared;
139
140    /** Thread number of the miss. */
141    ThreadID threadNum;
142    /** The number of currently allocated targets. */
143    short ntargets;
144
145
146    /** Data buffer (if needed).  Currently used only for pending
147     * upgrade handling. */
148    uint8_t *data;
149
150    /**
151     * Pointer to this MSHR on the ready list.
152     * @sa MissQueue, MSHRQueue::readyList
153     */
154    Iterator readyIter;
155
156    /**
157     * Pointer to this MSHR on the allocated list.
158     * @sa MissQueue, MSHRQueue::allocatedList
159     */
160    Iterator allocIter;
161
162private:
163    /** List of all requests that match the address */
164    TargetList *targets;
165
166    TargetList *deferredTargets;
167
168public:
169
170    bool isUncacheable() { return _isUncacheable; }
171
172    /**
173     * Allocate a miss to this MSHR.
174     * @param cmd The requesting command.
175     * @param addr The address of the miss.
176     * @param asid The address space id of the miss.
177     * @param size The number of bytes to request.
178     * @param pkt  The original miss.
179     */
180    void allocate(Addr addr, int size, PacketPtr pkt,
181                  Tick when, Counter _order);
182
183    bool markInService();
184
185    void clearDownstreamPending();
186
187    /**
188     * Mark this MSHR as free.
189     */
190    void deallocate();
191
192    /**
193     * Add a request to the list of targets.
194     * @param target The target.
195     */
196    void allocateTarget(PacketPtr target, Tick when, Counter order);
197    bool handleSnoop(PacketPtr target, Counter order);
198
199    /** A simple constructor. */
200    MSHR();
201    /** A simple destructor. */
202    ~MSHR();
203
204    /**
205     * Returns the current number of allocated targets.
206     * @return The current number of allocated targets.
207     */
208    int getNumTargets() const { return ntargets; }
209
210    /**
211     * Returns a pointer to the target list.
212     * @return a pointer to the target list.
213     */
214    TargetList *getTargetList() { return targets; }
215
216    /**
217     * Returns true if there are targets left.
218     * @return true if there are targets
219     */
220    bool hasTargets() const { return !targets->empty(); }
221
222    /**
223     * Returns a reference to the first target.
224     * @return A pointer to the first target.
225     */
226    Target *getTarget() const
227    {
228        assert(hasTargets());
229        return &targets->front();
230    }
231
232    /**
233     * Pop first target.
234     */
235    void popTarget()
236    {
237        --ntargets;
238        targets->pop_front();
239    }
240
241    bool isForwardNoResponse() const
242    {
243        if (getNumTargets() != 1)
244            return false;
245        Target *tgt = getTarget();
246        return tgt->source == Target::FromCPU && !tgt->pkt->needsResponse();
247    }
248
249    bool promoteDeferredTargets();
250
251    void handleFill(Packet *pkt, CacheBlk *blk);
252
253    bool checkFunctional(PacketPtr pkt);
254
255    /**
256     * Prints the contents of this MSHR for debugging.
257     */
258    void print(std::ostream &os,
259               int verbosity = 0,
260               const std::string &prefix = "") const;
261};
262
263#endif //__MSHR_HH__
264