mshr_queue.hh revision 4626 
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
78    /**
79     * Create a queue with a given number of entries.
80     * @param num_entrys The number of entries in this queue.
81     * @param reserve The minimum number of entries needed to satisfy
82     * any access.
83     */
84    MSHRQueue(int num_entries, int reserve = 1);
85
86    /** Destructor */
87    ~MSHRQueue();
88
89    /**
90     * Find the first MSHR that matches the provided address.
91     * @param addr The address to find.
92     * @return Pointer to the matching MSHR, null if not found.
93     */
94    MSHR *findMatch(Addr addr) const;
95
96    /**
97     * Find and return all the matching entries in the provided vector.
98     * @param addr The address to find.
99     * @param matches The vector to return pointers to the matching entries.
100     * @return True if any matches are found, false otherwise.
101     * @todo Typedef the vector??
102     */
103    bool findMatches(Addr addr, std::vector<MSHR*>& matches) const;
104
105    /**
106     * Find any pending requests that overlap the given request.
107     * @param pkt The request to find.
108     * @return A pointer to the earliest matching MSHR.
109     */
110    MSHR *findPending(Addr addr, int size) const;
111
112    /**
113     * Allocates a new MSHR for the request and size. This places the request
114     * as the first target in the MSHR.
115     * @param pkt The request to handle.
116     * @param size The number in bytes to fetch from memory.
117     * @return The a pointer to the MSHR allocated.
118     *
119     * @pre There are free entries.
120     */
121    MSHR *allocate(Addr addr, int size, PacketPtr &pkt, bool isFill);
122
123    /**
124     * Removes the given MSHR from the queue. This places the MSHR on the
125     * free list.
126     * @param mshr
127     */
128    void deallocate(MSHR *mshr);
129
130    /**
131     * Remove a MSHR from the queue. Returns an iterator into the
132     * allocatedList for faster squash implementation.
133     * @param mshr The MSHR to remove.
134     * @return An iterator to the next entry in the allocatedList.
135     */
136    MSHR::Iterator deallocateOne(MSHR *mshr);
137
138    /**
139     * Moves the MSHR to the front of the pending list if it is not
140     * in service.
141     * @param mshr The entry to move.
142     */
143    void moveToFront(MSHR *mshr);
144
145    /**
146     * Mark the given MSHR as in service. This removes the MSHR from the
147     * pendingList. Deallocates the MSHR if it does not expect a response.
148     * @param mshr The MSHR to mark in service.
149     */
150    void markInService(MSHR *mshr);
151
152    /**
153     * Mark an in service entry as pending, used to resend a request.
154     * @param mshr The MSHR to resend.
155     */
156    void markPending(MSHR *mshr);
157
158    /**
159     * Squash outstanding requests with the given thread number. If a request
160     * is in service, just squashes the targets.
161     * @param threadNum The thread to squash.
162     */
163    void squash(int threadNum);
164
165    /**
166     * Returns true if the pending list is not empty.
167     * @return True if there are outstanding requests.
168     */
169    bool havePending() const
170    {
171        return !pendingList.empty();
172    }
173
174    /**
175     * Returns true if there are no free entries.
176     * @return True if this queue is full.
177     */
178    bool isFull() const
179    {
180        return (allocated > numEntries - numReserve);
181    }
182
183    /**
184     * Returns the MSHR at the head of the pendingList.
185     * @return The next request to service.
186     */
187    MSHR *getNextMSHR() const
188    {
189        if (pendingList.empty()) {
190            return NULL;
191        }
192        return pendingList.front();
193    }
194};
195
196#endif //__MEM__CACHE__MISS__MSHR_QUEUE_HH__
197