src/mem/packet_queue.cc

   1 /*
   2  * Copyright (c) 2012,2015,2018-2020 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) 2006 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
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  20  * notice, this list of conditions and the following disclaimer;
  21  * redistributions in binary form must reproduce the above copyright
  22  * notice, this list of conditions and the following disclaimer in the
  23  * documentation and/or other materials provided with the distribution;
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  25  * contributors may be used to endorse or promote products derived from
  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,
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  34  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  35  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  36  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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  38  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  39  */
  40
  41 #include "mem/packet_queue.hh"
  42
  43 #include "base/trace.hh"
  44 #include "debug/Drain.hh"
  45 #include "debug/PacketQueue.hh"
  46
  47 PacketQueue::PacketQueue(EventManager& _em, const std::string& _label,
  48                          const std::string& _sendEventName,
  49                          bool force_order,
  50                          bool disable_sanity_check)
  51     : em(_em), sendEvent([this]{ processSendEvent(); }, _sendEventName),
  52       _disableSanityCheck(disable_sanity_check),
  53       forceOrder(force_order),
  54       label(_label), waitingOnRetry(false)
  55 {
  56 }
  57
  58 PacketQueue::~PacketQueue()
  59 {
  60 }
  61
  62 void
  63 PacketQueue::retry()
  64 {
  65     DPRINTF(PacketQueue, "Queue %s received retry\n", name());
  66     assert(waitingOnRetry);
  67     waitingOnRetry = false;
  68     sendDeferredPacket();
  69 }
  70
  71 bool
  72 PacketQueue::checkConflict(const PacketPtr pkt, const int blk_size) const
  73 {
  74     // caller is responsible for ensuring that all packets have the
  75     // same alignment
  76     for (const auto& p : transmitList) {
  77         if (p.pkt->matchBlockAddr(pkt, blk_size))
  78             return true;
  79     }
  80     return false;
  81 }
  82
  83 bool
  84 PacketQueue::trySatisfyFunctional(PacketPtr pkt)
  85 {
  86     pkt->pushLabel(label);
  87
  88     auto i = transmitList.begin();
  89     bool found = false;
  90
  91     while (!found && i != transmitList.end()) {
  92         // If the buffered packet contains data, and it overlaps the
  93         // current packet, then update data
  94         found = pkt->trySatisfyFunctional(i->pkt);
  95         ++i;
  96     }
  97
  98     pkt->popLabel();
  99
 100     return found;
 101 }
 102
 103 void
 104 PacketQueue::schedSendTiming(PacketPtr pkt, Tick when)
 105 {
 106     DPRINTF(PacketQueue, "%s for %s address %x size %d when %lu ord: %i\n",
 107             __func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize(), when,
 108             forceOrder);
 109
 110     // we can still send a packet before the end of this tick
 111     assert(when >= curTick());
 112
 113     // express snoops should never be queued
 114     assert(!pkt->isExpressSnoop());
 115
 116     // add a very basic sanity check on the port to ensure the
 117     // invisible buffer is not growing beyond reasonable limits
 118     if (!_disableSanityCheck && transmitList.size() > 128) {
 119         panic("Packet queue %s has grown beyond 128 packets\n",
 120               name());
 121     }
 122
 123     // we should either have an outstanding retry, or a send event
 124     // scheduled, but there is an unfortunate corner case where the
 125     // x86 page-table walker and timing CPU send out a new request as
 126     // part of the receiving of a response (called by
 127     // PacketQueue::sendDeferredPacket), in which we end up calling
 128     // ourselves again before we had a chance to update waitingOnRetry
 129     // assert(waitingOnRetry || sendEvent.scheduled());
 130
 131     // this belongs in the middle somewhere, so search from the end to
 132     // order by tick; however, if forceOrder is set, also make sure
 133     // not to re-order in front of some existing packet with the same
 134     // address
 135     auto it = transmitList.end();
 136     while (it != transmitList.begin()) {
 137         --it;
 138         if ((forceOrder && it->pkt->matchAddr(pkt)) || it->tick <= when) {
 139             // emplace inserts the element before the position pointed to by
 140             // the iterator, so advance it one step
 141             transmitList.emplace(++it, when, pkt);
 142             return;
 143         }
 144     }
 145     // either the packet list is empty or this has to be inserted
 146     // before every other packet
 147     transmitList.emplace_front(when, pkt);
 148     schedSendEvent(when);
 149 }
 150
 151 void
 152 PacketQueue::schedSendEvent(Tick when)
 153 {
 154     // if we are waiting on a retry just hold off
 155     if (waitingOnRetry) {
 156         DPRINTF(PacketQueue, "Not scheduling send as waiting for retry\n");
 157         assert(!sendEvent.scheduled());
 158         return;
 159     }
 160
 161     if (when != MaxTick) {
 162         // we cannot go back in time, and to be consistent we stick to
 163         // one tick in the future
 164         when = std::max(when, curTick() + 1);
 165         // @todo Revisit the +1
 166
 167         if (!sendEvent.scheduled()) {
 168             em.schedule(&sendEvent, when);
 169         } else if (when < sendEvent.when()) {
 170             // if the new time is earlier than when the event
 171             // currently is scheduled, move it forward
 172             em.reschedule(&sendEvent, when);
 173         }
 174     } else {
 175         // we get a MaxTick when there is no more to send, so if we're
 176         // draining, we may be done at this point
 177         if (drainState() == DrainState::Draining &&
 178             transmitList.empty() && !sendEvent.scheduled()) {
 179
 180             DPRINTF(Drain, "PacketQueue done draining,"
 181                     "processing drain event\n");
 182             signalDrainDone();
 183         }
 184     }
 185 }
 186
 187 void
 188 PacketQueue::sendDeferredPacket()
 189 {
 190     // sanity checks
 191     assert(!waitingOnRetry);
 192     assert(deferredPacketReady());
 193
 194     DeferredPacket dp = transmitList.front();
 195
 196     // take the packet of the list before sending it, as sending of
 197     // the packet in some cases causes a new packet to be enqueued
 198     // (most notaly when responding to the timing CPU, leading to a
 199     // new request hitting in the L1 icache, leading to a new
 200     // response)
 201     transmitList.pop_front();
 202
 203     // use the appropriate implementation of sendTiming based on the
 204     // type of queue
 205     waitingOnRetry = !sendTiming(dp.pkt);
 206
 207     // if we succeeded and are not waiting for a retry, schedule the
 208     // next send
 209     if (!waitingOnRetry) {
 210         schedSendEvent(deferredPacketReadyTime());
 211     } else {
 212         // put the packet back at the front of the list
 213         transmitList.emplace_front(dp);
 214     }
 215 }
 216
 217 void
 218 PacketQueue::processSendEvent()
 219 {
 220     assert(!waitingOnRetry);
 221     sendDeferredPacket();
 222 }
 223
 224 DrainState
 225 PacketQueue::drain()
 226 {
 227     if (transmitList.empty()) {
 228         return DrainState::Drained;
 229     } else {
 230         DPRINTF(Drain, "PacketQueue not drained\n");
 231         return DrainState::Draining;
 232     }
 233 }
 234
 235 ReqPacketQueue::ReqPacketQueue(EventManager& _em, RequestPort& _mem_side_port,
 236                                const std::string _label)
 237     : PacketQueue(_em, _label, name(_mem_side_port, _label)),
 238       memSidePort(_mem_side_port)
 239 {
 240 }
 241
 242 bool
 243 ReqPacketQueue::sendTiming(PacketPtr pkt)
 244 {
 245     return memSidePort.sendTimingReq(pkt);
 246 }
 247
 248 SnoopRespPacketQueue::SnoopRespPacketQueue(EventManager& _em,
 249                                            RequestPort& _mem_side_port,
 250                                            bool force_order,
 251                                            const std::string _label)
 252     : PacketQueue(_em, _label, name(_mem_side_port, _label), force_order),
 253       memSidePort(_mem_side_port)
 254 {
 255 }
 256
 257 bool
 258 SnoopRespPacketQueue::sendTiming(PacketPtr pkt)
 259 {
 260     return memSidePort.sendTimingSnoopResp(pkt);
 261 }
 262
 263 RespPacketQueue::RespPacketQueue(EventManager& _em,
 264                                  ResponsePort& _cpu_side_port,
 265                                  bool force_order,
 266                                  const std::string _label)
 267     : PacketQueue(_em, _label, name(_cpu_side_port, _label), force_order),
 268       cpuSidePort(_cpu_side_port)
 269 {
 270 }
 271
 272 bool
 273 RespPacketQueue::sendTiming(PacketPtr pkt)
 274 {
 275     return cpuSidePort.sendTimingResp(pkt);
 276 }