mshr_queue.hh revision 11197 
1/*
2 * Copyright (c) 2012-2013, 2015 ARM Limited
3 * All rights reserved.
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2003-2005 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
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24 * neither the name of the copyright holders nor the names of its
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26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Erik Hallnor
41 *          Andreas Sandberg
42 */
43
44/** @file
45 * Declaration of a structure to manage MSHRs.
46 */
47
48#ifndef __MEM_CACHE_MSHR_QUEUE_HH__
49#define __MEM_CACHE_MSHR_QUEUE_HH__
50
51#include <vector>
52
53#include "mem/cache/mshr.hh"
54#include "mem/packet.hh"
55#include "sim/drain.hh"
56
57/**
58 * A Class for maintaining a list of pending and allocated memory requests.
59 */
60class MSHRQueue : public Drainable
61{
62  private:
63    /** Local label (for functional print requests) */
64    const std::string label;
65
66    // Parameters
67    /**
68     * The total number of entries in this queue. This number is set as the
69     * number of entries requested plus (numReserve - 1). This allows for
70     * the same number of effective entries while still maintaining the reserve.
71     */
72    const int numEntries;
73
74    /**
75     * The number of entries to hold in reserve. This is needed because copy
76     * operations can allocate upto 4 entries at one time.
77     */
78    const int numReserve;
79
80    /**
81     * The number of entries to reserve for future demand accesses.
82     * Prevent prefetcher from taking all mshr entries
83     */
84    const int demandReserve;
85
86    /**  MSHR storage. */
87    std::vector<MSHR> registers;
88    /** Holds pointers to all allocated entries. */
89    MSHR::List allocatedList;
90    /** Holds pointers to entries that haven't been sent to the bus. */
91    MSHR::List readyList;
92    /** Holds non allocated entries. */
93    MSHR::List freeList;
94
95    MSHR::Iterator addToReadyList(MSHR *mshr);
96
97
98  public:
99    /** The number of allocated entries. */
100    int allocated;
101    /** The number of entries that have been forwarded to the bus. */
102    int inServiceEntries;
103    /** The index of this queue within the cache (MSHR queue vs. write
104     * buffer). */
105    const int index;
106
107    /**
108     * Create a queue with a given number of entries.
109     * @param num_entrys The number of entries in this queue.
110     * @param reserve The minimum number of entries needed to satisfy
111     * any access.
112     * @param demand_reserve The minimum number of entries needed to satisfy
113     * demand accesses.
114     */
115    MSHRQueue(const std::string &_label, int num_entries, int reserve,
116              int demand_reserve, int index);
117
118    /**
119     * Find the first MSHR that matches the provided address.
120     * @param blk_addr The block address to find.
121     * @param is_secure True if the target memory space is secure.
122     * @return Pointer to the matching MSHR, null if not found.
123     */
124    MSHR *findMatch(Addr blk_addr, bool is_secure) const;
125
126    /**
127     * Find and return all the matching entries in the provided vector.
128     * @param blk_addr The block  address to find.
129     * @param is_secure True if the target memory space is secure.
130     * @param matches The vector to return pointers to the matching entries.
131     * @return True if any matches are found, false otherwise.
132     */
133    bool findMatches(Addr blk_addr, bool is_secure,
134                     std::vector<MSHR*>& matches) const;
135
136    /**
137     * Find any pending requests that overlap the given request.
138     * @param blk_addr Block address.
139     * @param is_secure True if the target memory space is secure.
140     * @return A pointer to the earliest matching MSHR.
141     */
142    MSHR *findPending(Addr blk_addr, bool is_secure) const;
143
144    bool checkFunctional(PacketPtr pkt, Addr blk_addr);
145
146    /**
147     * Allocates a new MSHR for the request and size. This places the request
148     * as the first target in the MSHR.
149     *
150     * @param blk_addr The address of the block.
151     * @param blk_size The number of bytes to request.
152     * @param pkt The original miss.
153     * @param when_ready When should the MSHR be ready to act upon.
154     * @param order The logical order of this MSHR
155     * @param alloc_on_fill Should the cache allocate a block on fill
156     *
157     * @return The a pointer to the MSHR allocated.
158     *
159     * @pre There are free entries.
160     */
161    MSHR *allocate(Addr blk_addr, unsigned blk_size, PacketPtr pkt,
162                   Tick when_ready, Counter order, bool alloc_on_fill);
163
164    /**
165     * Removes the given MSHR from the queue. This places the MSHR on the
166     * free list.
167     * @param mshr
168     */
169    void deallocate(MSHR *mshr);
170
171    /**
172     * Remove a MSHR from the queue. Returns an iterator into the
173     * allocatedList for faster squash implementation.
174     * @param mshr The MSHR to remove.
175     * @return An iterator to the next entry in the allocatedList.
176     */
177    MSHR::Iterator deallocateOne(MSHR *mshr);
178
179    /**
180     * Moves the MSHR to the front of the pending list if it is not
181     * in service.
182     * @param mshr The entry to move.
183     */
184    void moveToFront(MSHR *mshr);
185
186    /**
187     * Mark the given MSHR as in service. This removes the MSHR from the
188     * readyList or deallocates the MSHR if it does not expect a response.
189     *
190     * @param mshr The MSHR to mark in service.
191     * @param pending_dirty_resp Whether we expect a dirty response
192     *                           from another cache
193     */
194    void markInService(MSHR *mshr, bool pending_dirty_resp);
195
196    /**
197     * Mark an in service entry as pending, used to resend a request.
198     * @param mshr The MSHR to resend.
199     */
200    void markPending(MSHR *mshr);
201
202    /**
203     * Squash outstanding requests with the given thread number. If a request
204     * is in service, just squashes the targets.
205     * @param threadNum The thread to squash.
206     */
207    void squash(int threadNum);
208
209    /**
210     * Deallocate top target, possibly freeing the MSHR
211     * @return if MSHR queue is no longer full
212     */
213    bool forceDeallocateTarget(MSHR *mshr);
214
215    /**
216     * Returns true if the pending list is not empty.
217     * @return True if there are outstanding requests.
218     */
219    bool havePending() const
220    {
221        return !readyList.empty();
222    }
223
224    /**
225     * Returns true if there are no free entries.
226     * @return True if this queue is full.
227     */
228    bool isFull() const
229    {
230        return (allocated > numEntries - numReserve);
231    }
232
233    /**
234     * Returns true if sufficient mshrs for prefetch.
235     * @return True if sufficient mshrs for prefetch.
236     */
237    bool canPrefetch() const
238    {
239        return (allocated < numEntries - (numReserve + demandReserve));
240    }
241
242    /**
243     * Returns the MSHR at the head of the readyList.
244     * @return The next request to service.
245     */
246    MSHR *getNextMSHR() const
247    {
248        if (readyList.empty() || readyList.front()->readyTime > curTick()) {
249            return NULL;
250        }
251        return readyList.front();
252    }
253
254    Tick nextMSHRReadyTime() const
255    {
256        return readyList.empty() ? MaxTick : readyList.front()->readyTime;
257    }
258
259    DrainState drain() override;
260};
261
262#endif //__MEM_CACHE_MSHR_QUEUE_HH__
263