mshr_queue.hh revision 4920 
1/*
2 * Copyright (c) 2003-2005 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/** @file
32 * Declaration of a structure to manage MSHRs.
33 */
34
35#ifndef __MEM__CACHE__MISS__MSHR_QUEUE_HH__
36#define __MEM__CACHE__MISS__MSHR_QUEUE_HH__
37
38#include <vector>
39
40#include "mem/packet.hh"
41#include "mem/cache/miss/mshr.hh"
42
43/**
44 * A Class for maintaining a list of pending and allocated memory requests.
45 */
46class MSHRQueue
47{
48  private:
49    /**  MSHR storage. */
50    MSHR *registers;
51    /** Holds pointers to all allocated entries. */
52    MSHR::List allocatedList;
53    /** Holds pointers to entries that haven't been sent to the bus. */
54    MSHR::List readyList;
55    /** Holds non allocated entries. */
56    MSHR::List freeList;
57
58    // Parameters
59    /**
60     * The total number of entries in this queue. This number is set as the
61     * number of entries requested plus (numReserve - 1). This allows for
62     * the same number of effective entries while still maintaining the reserve.
63     */
64    const int numEntries;
65
66    /**
67     * The number of entries to hold in reserve. This is needed because copy
68     * operations can allocate upto 4 entries at one time.
69     */
70    const int numReserve;
71
72    MSHR::Iterator addToReadyList(MSHR *mshr);
73
74
75  public:
76    /** The number of allocated entries. */
77    int allocated;
78    /** The number of entries that have been forwarded to the bus. */
79    int inServiceEntries;
80    /** The index of this queue within the cache (MSHR queue vs. write
81     * buffer). */
82    const int index;
83
84    /**
85     * Create a queue with a given number of entries.
86     * @param num_entrys The number of entries in this queue.
87     * @param reserve The minimum number of entries needed to satisfy
88     * any access.
89     */
90    MSHRQueue(int num_entries, int reserve, int index);
91
92    /** Destructor */
93    ~MSHRQueue();
94
95    /**
96     * Find the first MSHR that matches the provided address.
97     * @param addr The address to find.
98     * @return Pointer to the matching MSHR, null if not found.
99     */
100    MSHR *findMatch(Addr addr) const;
101
102    /**
103     * Find and return all the matching entries in the provided vector.
104     * @param addr The address to find.
105     * @param matches The vector to return pointers to the matching entries.
106     * @return True if any matches are found, false otherwise.
107     * @todo Typedef the vector??
108     */
109    bool findMatches(Addr addr, std::vector<MSHR*>& matches) const;
110
111    /**
112     * Find any pending requests that overlap the given request.
113     * @param pkt The request to find.
114     * @return A pointer to the earliest matching MSHR.
115     */
116    MSHR *findPending(Addr addr, int size) const;
117
118    bool checkFunctional(PacketPtr pkt, Addr blk_addr);
119
120    /**
121     * Allocates a new MSHR for the request and size. This places the request
122     * as the first target in the MSHR.
123     * @param pkt The request to handle.
124     * @param size The number in bytes to fetch from memory.
125     * @return The a pointer to the MSHR allocated.
126     *
127     * @pre There are free entries.
128     */
129    MSHR *allocate(Addr addr, int size, PacketPtr &pkt,
130                   Tick when, Counter order);
131
132    /**
133     * Removes the given MSHR from the queue. This places the MSHR on the
134     * free list.
135     * @param mshr
136     */
137    void deallocate(MSHR *mshr);
138
139    /**
140     * Remove a MSHR from the queue. Returns an iterator into the
141     * allocatedList for faster squash implementation.
142     * @param mshr The MSHR to remove.
143     * @return An iterator to the next entry in the allocatedList.
144     */
145    MSHR::Iterator deallocateOne(MSHR *mshr);
146
147    /**
148     * Moves the MSHR to the front of the pending list if it is not
149     * in service.
150     * @param mshr The entry to move.
151     */
152    void moveToFront(MSHR *mshr);
153
154    /**
155     * Mark the given MSHR as in service. This removes the MSHR from the
156     * readyList. Deallocates the MSHR if it does not expect a response.
157     * @param mshr The MSHR to mark in service.
158     */
159    void markInService(MSHR *mshr);
160
161    /**
162     * Mark an in service entry as pending, used to resend a request.
163     * @param mshr The MSHR to resend.
164     */
165    void markPending(MSHR *mshr);
166
167    /**
168     * Squash outstanding requests with the given thread number. If a request
169     * is in service, just squashes the targets.
170     * @param threadNum The thread to squash.
171     */
172    void squash(int threadNum);
173
174    /**
175     * Returns true if the pending list is not empty.
176     * @return True if there are outstanding requests.
177     */
178    bool havePending() const
179    {
180        return !readyList.empty();
181    }
182
183    /**
184     * Returns true if there are no free entries.
185     * @return True if this queue is full.
186     */
187    bool isFull() const
188    {
189        return (allocated > numEntries - numReserve);
190    }
191
192    /**
193     * Returns the MSHR at the head of the readyList.
194     * @return The next request to service.
195     */
196    MSHR *getNextMSHR() const
197    {
198        if (readyList.empty() || readyList.front()->readyTime > curTick) {
199            return NULL;
200        }
201        return readyList.front();
202    }
203
204    Tick nextMSHRReadyTime() const
205    {
206        return readyList.empty() ? MaxTick : readyList.front()->readyTime;
207    }
208};
209
210#endif //__MEM__CACHE__MISS__MSHR_QUEUE_HH__
211