mshr_queue.hh revision 12727:56c23b54bcb1 
1/*
2 * Copyright (c) 2012-2013, 2015-2016 ARM Limited
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4 *
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8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
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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
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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,
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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 <string>
52
53#include "base/types.hh"
54#include "mem/cache/mshr.hh"
55#include "mem/cache/queue.hh"
56#include "mem/packet.hh"
57
58/**
59 * A Class for maintaining a list of pending and allocated memory requests.
60 */
61class MSHRQueue : public Queue<MSHR>
62{
63  private:
64
65    /**
66     * The number of entries to reserve for future demand accesses.
67     * Prevent prefetcher from taking all mshr entries
68     */
69    const int demandReserve;
70
71  public:
72
73    /**
74     * Create a queue with a given number of entries.
75     * @param num_entrys The number of entries in this queue.
76     * @param reserve The minimum number of entries needed to satisfy
77     * any access.
78     * @param demand_reserve The minimum number of entries needed to satisfy
79     * demand accesses.
80     */
81    MSHRQueue(const std::string &_label, int num_entries, int reserve,
82              int demand_reserve);
83
84    /**
85     * Allocates a new MSHR for the request and size. This places the request
86     * as the first target in the MSHR.
87     *
88     * @param blk_addr The address of the block.
89     * @param blk_size The number of bytes to request.
90     * @param pkt The original miss.
91     * @param when_ready When should the MSHR be ready to act upon.
92     * @param order The logical order of this MSHR
93     * @param alloc_on_fill Should the cache allocate a block on fill
94     *
95     * @return The a pointer to the MSHR allocated.
96     *
97     * @pre There are free entries.
98     */
99    MSHR *allocate(Addr blk_addr, unsigned blk_size, PacketPtr pkt,
100                   Tick when_ready, Counter order, bool alloc_on_fill);
101
102    /**
103     * Moves the MSHR to the front of the pending list if it is not
104     * in service.
105     * @param mshr The entry to move.
106     */
107    void moveToFront(MSHR *mshr);
108
109    /**
110     * Mark the given MSHR as in service. This removes the MSHR from the
111     * readyList or deallocates the MSHR if it does not expect a response.
112     *
113     * @param mshr The MSHR to mark in service.
114     * @param pending_modified_resp Whether we expect a modified response
115     *                              from another cache
116     */
117    void markInService(MSHR *mshr, bool pending_modified_resp);
118
119    /**
120     * Mark an in service entry as pending, used to resend a request.
121     * @param mshr The MSHR to resend.
122     */
123    void markPending(MSHR *mshr);
124
125    /**
126     * Deallocate top target, possibly freeing the MSHR
127     * @return if MSHR queue is no longer full
128     */
129    bool forceDeallocateTarget(MSHR *mshr);
130
131    /**
132     * Returns true if the pending list is not empty.
133     * @return True if there are outstanding requests.
134     */
135    bool havePending() const
136    {
137        return !readyList.empty();
138    }
139
140    /**
141     * Returns true if sufficient mshrs for prefetch.
142     * @return True if sufficient mshrs for prefetch.
143     */
144    bool canPrefetch() const
145    {
146        // @todo we may want to revisit the +1, currently added to
147        // keep regressions unchanged
148        return (allocated < numEntries - (numReserve + 1 + demandReserve));
149    }
150};
151
152#endif //__MEM_CACHE_MSHR_QUEUE_HH__
153