src/mem/cache/queue.hh

   1 /*
   2  * Copyright (c) 2012-2013, 2015-2016, 2018 ARM Limited
   3  * All rights reserved.
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   5  * The license below extends only to copyright in the software and shall
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   8  * to a hardware implementation of the functionality of the software
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  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.
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  26  * this software without specific prior written permission.
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  39  */
  40
  41 /** @file
  42  * Declaration of a high-level queue structure
  43  */
  44
  45 #ifndef __MEM_CACHE_QUEUE_HH__
  46 #define __MEM_CACHE_QUEUE_HH__
  47
  48 #include <cassert>
  49 #include <string>
  50 #include <type_traits>
  51
  52 #include "base/logging.hh"
  53 #include "base/trace.hh"
  54 #include "base/types.hh"
  55 #include "debug/Drain.hh"
  56 #include "mem/cache/queue_entry.hh"
  57 #include "mem/packet.hh"
  58 #include "sim/core.hh"
  59 #include "sim/drain.hh"
  60
  61 /**
  62  * A high-level queue interface, to be used by both the MSHR queue and
  63  * the write buffer.
  64  */
  65 template<class Entry>
  66 class Queue : public Drainable
  67 {
  68     static_assert(std::is_base_of<QueueEntry, Entry>::value,
  69         "Entry must be derived from QueueEntry");
  70
  71   protected:
  72     /** Local label (for functional print requests) */
  73     const std::string label;
  74
  75     /**
  76      * The total number of entries in this queue. This number is set
  77      * as the number of entries requested plus any reserve. This
  78      * allows for the same number of effective entries while still
  79      * maintaining an overflow reserve.
  80      */
  81     const int numEntries;
  82
  83     /**
  84      * The number of entries to hold as a temporary overflow
  85      * space. This is used to allow temporary overflow of the number
  86      * of entries as we only check the full condition under certain
  87      * conditions.
  88      */
  89     const int numReserve;
  90
  91     /**  Actual storage. */
  92     std::vector<Entry> entries;
  93     /** Holds pointers to all allocated entries. */
  94     typename Entry::List allocatedList;
  95     /** Holds pointers to entries that haven't been sent downstream. */
  96     typename Entry::List readyList;
  97     /** Holds non allocated entries. */
  98     typename Entry::List freeList;
  99
 100     typename Entry::Iterator addToReadyList(Entry* entry)
 101     {
 102         if (readyList.empty() ||
 103             readyList.back()->readyTime <= entry->readyTime) {
 104             return readyList.insert(readyList.end(), entry);
 105         }
 106
 107         for (auto i = readyList.begin(); i != readyList.end(); ++i) {
 108             if ((*i)->readyTime > entry->readyTime) {
 109                 return readyList.insert(i, entry);
 110             }
 111         }
 112         panic("Failed to add to ready list.");
 113     }
 114
 115     /** The number of entries that are in service. */
 116     int _numInService;
 117
 118     /** The number of currently allocated entries. */
 119     int allocated;
 120
 121   public:
 122
 123     /**
 124      * Create a queue with a given number of entries.
 125      *
 126      * @param num_entries The number of entries in this queue.
 127      * @param reserve The extra overflow entries needed.
 128      */
 129     Queue(const std::string &_label, int num_entries, int reserve) :
 130         label(_label), numEntries(num_entries + reserve),
 131         numReserve(reserve), entries(numEntries), _numInService(0),
 132         allocated(0)
 133     {
 134         for (int i = 0; i < numEntries; ++i) {
 135             freeList.push_back(&entries[i]);
 136         }
 137     }
 138
 139     bool isEmpty() const
 140     {
 141         return allocated == 0;
 142     }
 143
 144     bool isFull() const
 145     {
 146         return (allocated >= numEntries - numReserve);
 147     }
 148
 149     int numInService() const
 150     {
 151         return _numInService;
 152     }
 153
 154     /**
 155      * Find the first entry that matches the provided address.
 156      *
 157      * @param blk_addr The block address to find.
 158      * @param is_secure True if the target memory space is secure.
 159      * @param ignore_uncacheable Should uncacheables be ignored or not
 160      * @return Pointer to the matching WriteQueueEntry, null if not found.
 161      */
 162     Entry* findMatch(Addr blk_addr, bool is_secure,
 163                      bool ignore_uncacheable = true) const
 164     {
 165         for (const auto& entry : allocatedList) {
 166             // we ignore any entries allocated for uncacheable
 167             // accesses and simply ignore them when matching, in the
 168             // cache we never check for matches when adding new
 169             // uncacheable entries, and we do not want normal
 170             // cacheable accesses being added to an WriteQueueEntry
 171             // serving an uncacheable access
 172             if (!(ignore_uncacheable && entry->isUncacheable()) &&
 173                 entry->matchBlockAddr(blk_addr, is_secure)) {
 174                 return entry;
 175             }
 176         }
 177         return nullptr;
 178     }
 179
 180     bool trySatisfyFunctional(PacketPtr pkt)
 181     {
 182         pkt->pushLabel(label);
 183         for (const auto& entry : allocatedList) {
 184             if (entry->matchBlockAddr(pkt) &&
 185                 entry->trySatisfyFunctional(pkt)) {
 186                 pkt->popLabel();
 187                 return true;
 188             }
 189         }
 190         pkt->popLabel();
 191         return false;
 192     }
 193
 194     /**
 195      * Find any pending requests that overlap the given request of a
 196      * different queue.
 197      *
 198      * @param entry The entry to be compared against.
 199      * @return A pointer to the earliest matching entry.
 200      */
 201     Entry* findPending(const QueueEntry* entry) const
 202     {
 203         for (const auto& ready_entry : readyList) {
 204             if (ready_entry->conflictAddr(entry)) {
 205                 return ready_entry;
 206             }
 207         }
 208         return nullptr;
 209     }
 210
 211     /**
 212      * Returns the WriteQueueEntry at the head of the readyList.
 213      * @return The next request to service.
 214      */
 215     Entry* getNext() const
 216     {
 217         if (readyList.empty() || readyList.front()->readyTime > curTick()) {
 218             return nullptr;
 219         }
 220         return readyList.front();
 221     }
 222
 223     Tick nextReadyTime() const
 224     {
 225         return readyList.empty() ? MaxTick : readyList.front()->readyTime;
 226     }
 227
 228     /**
 229      * Removes the given entry from the queue. This places the entry
 230      * on the free list.
 231      *
 232      * @param entry
 233      */
 234     void deallocate(Entry *entry)
 235     {
 236         allocatedList.erase(entry->allocIter);
 237         freeList.push_front(entry);
 238         allocated--;
 239         if (entry->inService) {
 240             _numInService--;
 241         } else {
 242             readyList.erase(entry->readyIter);
 243         }
 244         entry->deallocate();
 245         if (drainState() == DrainState::Draining && allocated == 0) {
 246             // Notify the drain manager that we have completed
 247             // draining if there are no other outstanding requests in
 248             // this queue.
 249             DPRINTF(Drain, "Queue now empty, signalling drained\n");
 250             signalDrainDone();
 251         }
 252     }
 253
 254     DrainState drain() override
 255     {
 256         return allocated == 0 ? DrainState::Drained : DrainState::Draining;
 257     }
 258 };
 259
 260 #endif //__MEM_CACHE_QUEUE_HH__