mshr_queue.hh revision 4666 
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    /**
119     * Allocates a new MSHR for the request and size. This places the request
120     * as the first target in the MSHR.
121     * @param pkt The request to handle.
122     * @param size The number in bytes to fetch from memory.
123     * @return The a pointer to the MSHR allocated.
124     *
125     * @pre There are free entries.
126     */
127    MSHR *allocate(Addr addr, int size, PacketPtr &pkt,
128                   Tick when, Counter order);
129
130    /**
131     * Removes the given MSHR from the queue. This places the MSHR on the
132     * free list.
133     * @param mshr
134     */
135    void deallocate(MSHR *mshr);
136
137    /**
138     * Remove a MSHR from the queue. Returns an iterator into the
139     * allocatedList for faster squash implementation.
140     * @param mshr The MSHR to remove.
141     * @return An iterator to the next entry in the allocatedList.
142     */
143    MSHR::Iterator deallocateOne(MSHR *mshr);
144
145    /**
146     * Moves the MSHR to the front of the pending list if it is not
147     * in service.
148     * @param mshr The entry to move.
149     */
150    void moveToFront(MSHR *mshr);
151
152    /**
153     * Mark the given MSHR as in service. This removes the MSHR from the
154     * readyList. Deallocates the MSHR if it does not expect a response.
155     * @param mshr The MSHR to mark in service.
156     */
157    void markInService(MSHR *mshr);
158
159    /**
160     * Mark an in service entry as pending, used to resend a request.
161     * @param mshr The MSHR to resend.
162     */
163    void markPending(MSHR *mshr);
164
165    /**
166     * Squash outstanding requests with the given thread number. If a request
167     * is in service, just squashes the targets.
168     * @param threadNum The thread to squash.
169     */
170    void squash(int threadNum);
171
172    /**
173     * Returns true if the pending list is not empty.
174     * @return True if there are outstanding requests.
175     */
176    bool havePending() const
177    {
178        return !readyList.empty();
179    }
180
181    /**
182     * Returns true if there are no free entries.
183     * @return True if this queue is full.
184     */
185    bool isFull() const
186    {
187        return (allocated > numEntries - numReserve);
188    }
189
190    /**
191     * Returns the MSHR at the head of the readyList.
192     * @return The next request to service.
193     */
194    MSHR *getNextMSHR() const
195    {
196        if (readyList.empty() || readyList.front()->readyTick > curTick) {
197            return NULL;
198        }
199        return readyList.front();
200    }
201
202    Tick nextMSHRReadyTick() const
203    {
204        return readyList.empty() ? MaxTick : readyList.front()->readyTick;
205    }
206};
207
208#endif //__MEM__CACHE__MISS__MSHR_QUEUE_HH__
209