mshr.hh revision 9264 
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 * @sa  \ref gem5MemorySystem "gem5 Memory System"
51 */
52class MSHR : public Packet::SenderState, public Printable
53{
54
55  public:
56
57    class Target {
58      public:
59
60        enum Source {
61            FromCPU,
62            FromSnoop,
63            FromPrefetcher
64        };
65
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?
73
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)
78        {}
79    };
80
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;
85
86      public:
87        bool needsExclusive;
88        bool hasUpgrade;
89
90        TargetList();
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;
100    };
101
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;
108
109    /** Pointer to queue containing this MSHR. */
110    MSHRQueue *queue;
111
112    /** Cycle when ready to issue */
113    Tick readyTime;
114
115    /** Order number assigned by the miss queue. */
116    Counter order;
117
118    /** Address of the request. */
119    Addr addr;
120
121    /** Size of the request. */
122    int size;
123
124    /** True if the request has been sent to the bus. */
125    bool inService;
126
127    /** True if the request is just a simple forward from an upper level */
128    bool isForward;
129
130    /** True if we need to get an exclusive copy of the block. */
131    bool needsExclusive() const { return targets->needsExclusive; }
132
133    /** True if the request is uncacheable */
134    bool _isUncacheable;
135
136    bool downstreamPending;
137
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.
141     */
142
143    /** Will we have a dirty copy after this request? */
144    bool pendingDirty;
145    bool isPendingDirty() const {
146        assert(inService); return pendingDirty;
147    }
148
149    /** Did we snoop an invalidate while waiting for data? */
150    bool postInvalidate;
151    bool hasPostInvalidate() const {
152        assert(inService); return postInvalidate;
153    }
154
155    /** Did we snoop a read while waiting for data? */
156    bool postDowngrade;
157    bool hasPostDowngrade() const {
158        assert(inService); return postDowngrade;
159    }
160
161    /** Thread number of the miss. */
162    ThreadID threadNum;
163    /** The number of currently allocated targets. */
164    unsigned short ntargets;
165
166
167    /** Data buffer (if needed).  Currently used only for pending
168     * upgrade handling. */
169    uint8_t *data;
170
171    /**
172     * Pointer to this MSHR on the ready list.
173     * @sa MissQueue, MSHRQueue::readyList
174     */
175    Iterator readyIter;
176
177    /**
178     * Pointer to this MSHR on the allocated list.
179     * @sa MissQueue, MSHRQueue::allocatedList
180     */
181    Iterator allocIter;
182
183private:
184    /** List of all requests that match the address */
185    TargetList *targets;
186
187    TargetList *deferredTargets;
188
189public:
190
191    bool isUncacheable() { return _isUncacheable; }
192
193    /**
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.
200     */
201    void allocate(Addr addr, int size, PacketPtr pkt,
202                  Tick when, Counter _order);
203
204    bool markInService(PacketPtr pkt);
205
206    void clearDownstreamPending();
207
208    /**
209     * Mark this MSHR as free.
210     */
211    void deallocate();
212
213    /**
214     * Add a request to the list of targets.
215     * @param target The target.
216     */
217    void allocateTarget(PacketPtr target, Tick when, Counter order);
218    bool handleSnoop(PacketPtr target, Counter order);
219
220    /** A simple constructor. */
221    MSHR();
222    /** A simple destructor. */
223    ~MSHR();
224
225    /**
226     * Returns the current number of allocated targets.
227     * @return The current number of allocated targets.
228     */
229    int getNumTargets() const { return ntargets; }
230
231    /**
232     * Returns a pointer to the target list.
233     * @return a pointer to the target list.
234     */
235    TargetList *getTargetList() { return targets; }
236
237    /**
238     * Returns true if there are targets left.
239     * @return true if there are targets
240     */
241    bool hasTargets() const { return !targets->empty(); }
242
243    /**
244     * Returns a reference to the first target.
245     * @return A pointer to the first target.
246     */
247    Target *getTarget() const
248    {
249        assert(hasTargets());
250        return &targets->front();
251    }
252
253    /**
254     * Pop first target.
255     */
256    void popTarget()
257    {
258        --ntargets;
259        targets->pop_front();
260    }
261
262    bool isForwardNoResponse() const
263    {
264        if (getNumTargets() != 1)
265            return false;
266        Target *tgt = getTarget();
267        return tgt->source == Target::FromCPU && !tgt->pkt->needsResponse();
268    }
269
270    bool promoteDeferredTargets();
271
272    void handleFill(Packet *pkt, CacheBlk *blk);
273
274    bool checkFunctional(PacketPtr pkt);
275
276    /**
277     * Prints the contents of this MSHR for debugging.
278     */
279    void print(std::ostream &os,
280               int verbosity = 0,
281               const std::string &prefix = "") const;
282};
283
284#endif //__MSHR_HH__
285