mshr_queue.hh revision 4628 
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 pendingList;
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  public:
73    /** The number of allocated entries. */
74    int allocated;
75    /** The number of entries that have been forwarded to the bus. */
76    int inServiceEntries;
77    /** The index of this queue within the cache (MSHR queue vs. write
78     * buffer). */
79    const int index;
80
81    /**
82     * Create a queue with a given number of entries.
83     * @param num_entrys The number of entries in this queue.
84     * @param reserve The minimum number of entries needed to satisfy
85     * any access.
86     */
87    MSHRQueue(int num_entries, int reserve, int index);
88
89    /** Destructor */
90    ~MSHRQueue();
91
92    /**
93     * Find the first MSHR that matches the provided address.
94     * @param addr The address to find.
95     * @return Pointer to the matching MSHR, null if not found.
96     */
97    MSHR *findMatch(Addr addr) const;
98
99    /**
100     * Find and return all the matching entries in the provided vector.
101     * @param addr The address to find.
102     * @param matches The vector to return pointers to the matching entries.
103     * @return True if any matches are found, false otherwise.
104     * @todo Typedef the vector??
105     */
106    bool findMatches(Addr addr, std::vector<MSHR*>& matches) const;
107
108    /**
109     * Find any pending requests that overlap the given request.
110     * @param pkt The request to find.
111     * @return A pointer to the earliest matching MSHR.
112     */
113    MSHR *findPending(Addr addr, int size) const;
114
115    /**
116     * Allocates a new MSHR for the request and size. This places the request
117     * as the first target in the MSHR.
118     * @param pkt The request to handle.
119     * @param size The number in bytes to fetch from memory.
120     * @return The a pointer to the MSHR allocated.
121     *
122     * @pre There are free entries.
123     */
124    MSHR *allocate(Addr addr, int size, PacketPtr &pkt);
125
126    /**
127     * Removes the given MSHR from the queue. This places the MSHR on the
128     * free list.
129     * @param mshr
130     */
131    void deallocate(MSHR *mshr);
132
133    /**
134     * Remove a MSHR from the queue. Returns an iterator into the
135     * allocatedList for faster squash implementation.
136     * @param mshr The MSHR to remove.
137     * @return An iterator to the next entry in the allocatedList.
138     */
139    MSHR::Iterator deallocateOne(MSHR *mshr);
140
141    /**
142     * Moves the MSHR to the front of the pending list if it is not
143     * in service.
144     * @param mshr The entry to move.
145     */
146    void moveToFront(MSHR *mshr);
147
148    /**
149     * Mark the given MSHR as in service. This removes the MSHR from the
150     * pendingList. Deallocates the MSHR if it does not expect a response.
151     * @param mshr The MSHR to mark in service.
152     */
153    void markInService(MSHR *mshr);
154
155    /**
156     * Mark an in service entry as pending, used to resend a request.
157     * @param mshr The MSHR to resend.
158     */
159    void markPending(MSHR *mshr);
160
161    /**
162     * Squash outstanding requests with the given thread number. If a request
163     * is in service, just squashes the targets.
164     * @param threadNum The thread to squash.
165     */
166    void squash(int threadNum);
167
168    /**
169     * Returns true if the pending list is not empty.
170     * @return True if there are outstanding requests.
171     */
172    bool havePending() const
173    {
174        return !pendingList.empty();
175    }
176
177    /**
178     * Returns true if there are no free entries.
179     * @return True if this queue is full.
180     */
181    bool isFull() const
182    {
183        return (allocated > numEntries - numReserve);
184    }
185
186    /**
187     * Returns the MSHR at the head of the pendingList.
188     * @return The next request to service.
189     */
190    MSHR *getNextMSHR() const
191    {
192        if (pendingList.empty()) {
193            return NULL;
194        }
195        return pendingList.front();
196    }
197};
198
199#endif //__MEM__CACHE__MISS__MSHR_QUEUE_HH__
200