src/mem/packet_queue.cc

   1 /*
   2  * Copyright (c) 2012,2015 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) 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
  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
  22  * notice, this list of conditions and the following disclaimer in the
  23  * documentation and/or other materials provided with the distribution;
  24  * neither the name of the copyright holders nor the names of its
  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,
  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
  36  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  37  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  38  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  39  *
  40  * Authors: Ali Saidi
  41  *          Andreas Hansson
  42  */
  43
  44 #include "base/trace.hh"
  45 #include "debug/Drain.hh"
  46 #include "debug/PacketQueue.hh"
  47 #include "mem/packet_queue.hh"
  48
  49 using namespace std;
  50
  51 PacketQueue::PacketQueue(EventManager& _em, const std::string& _label,
  52                          bool disable_sanity_check)
  53     : em(_em), sendEvent(this), _disableSanityCheck(disable_sanity_check),
  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::hasAddr(Addr addr) 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->getAddr() == addr)
  78             return true;
  79     }
  80     return false;
  81 }
  82
  83 bool
  84 PacketQueue::checkFunctional(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->checkFunctional(i->pkt);
  95         ++i;
  96     }
  97
  98     pkt->popLabel();
  99
 100     return found;
 101 }
 102
 103 void
 104 PacketQueue::schedSendTiming(PacketPtr pkt, Tick when, bool force_order)
 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             force_order);
 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() > 100) {
 119         panic("Packet queue %s has grown beyond 100 packets\n",
 120               name());
 121     }
 122
 123     // nothing on the list
 124     if (transmitList.empty()) {
 125         transmitList.emplace_front(when, pkt);
 126         schedSendEvent(when);
 127         return;
 128     }
 129
 130     // we should either have an outstanding retry, or a send event
 131     // scheduled, but there is an unfortunate corner case where the
 132     // x86 page-table walker and timing CPU send out a new request as
 133     // part of the receiving of a response (called by
 134     // PacketQueue::sendDeferredPacket), in which we end up calling
 135     // ourselves again before we had a chance to update waitingOnRetry
 136     // assert(waitingOnRetry || sendEvent.scheduled());
 137
 138     // this belongs in the middle somewhere, so search from the end to
 139     // order by tick; however, if force_order is set, also make sure
 140     // not to re-order in front of some existing packet with the same
 141     // address
 142     auto i = transmitList.end();
 143     --i;
 144     while (i != transmitList.begin() && when < i->tick &&
 145            !(force_order && i->pkt->getAddr() == pkt->getAddr()))
 146         --i;
 147
 148     // emplace inserts the element before the position pointed to by
 149     // the iterator, so advance it one step
 150     transmitList.emplace(++i, when, pkt);
 151 }
 152
 153 void
 154 PacketQueue::schedSendEvent(Tick when)
 155 {
 156     // if we are waiting on a retry just hold off
 157     if (waitingOnRetry) {
 158         DPRINTF(PacketQueue, "Not scheduling send as waiting for retry\n");
 159         assert(!sendEvent.scheduled());
 160         return;
 161     }
 162
 163     if (when != MaxTick) {
 164         // we cannot go back in time, and to be consistent we stick to
 165         // one tick in the future
 166         when = std::max(when, curTick() + 1);
 167         // @todo Revisit the +1
 168
 169         if (!sendEvent.scheduled()) {
 170             em.schedule(&sendEvent, when);
 171         } else if (when < sendEvent.when()) {
 172             // if the new time is earlier than when the event
 173             // currently is scheduled, move it forward
 174             em.reschedule(&sendEvent, when);
 175         }
 176     } else {
 177         // we get a MaxTick when there is no more to send, so if we're
 178         // draining, we may be done at this point
 179         if (drainState() == DrainState::Draining &&
 180             transmitList.empty() && !sendEvent.scheduled()) {
 181
 182             DPRINTF(Drain, "PacketQueue done draining,"
 183                     "processing drain event\n");
 184             signalDrainDone();
 185         }
 186     }
 187 }
 188
 189 void
 190 PacketQueue::sendDeferredPacket()
 191 {
 192     // sanity checks
 193     assert(!waitingOnRetry);
 194     assert(deferredPacketReady());
 195
 196     DeferredPacket dp = transmitList.front();
 197
 198     // take the packet of the list before sending it, as sending of
 199     // the packet in some cases causes a new packet to be enqueued
 200     // (most notaly when responding to the timing CPU, leading to a
 201     // new request hitting in the L1 icache, leading to a new
 202     // response)
 203     transmitList.pop_front();
 204
 205     // use the appropriate implementation of sendTiming based on the
 206     // type of queue
 207     waitingOnRetry = !sendTiming(dp.pkt);
 208
 209     // if we succeeded and are not waiting for a retry, schedule the
 210     // next send
 211     if (!waitingOnRetry) {
 212         schedSendEvent(deferredPacketReadyTime());
 213     } else {
 214         // put the packet back at the front of the list
 215         transmitList.emplace_front(dp);
 216     }
 217 }
 218
 219 void
 220 PacketQueue::processSendEvent()
 221 {
 222     assert(!waitingOnRetry);
 223     sendDeferredPacket();
 224 }
 225
 226 DrainState
 227 PacketQueue::drain()
 228 {
 229     if (transmitList.empty()) {
 230         return DrainState::Drained;
 231     } else {
 232         DPRINTF(Drain, "PacketQueue not drained\n");
 233         return DrainState::Draining;
 234     }
 235 }
 236
 237 ReqPacketQueue::ReqPacketQueue(EventManager& _em, MasterPort& _masterPort,
 238                                const std::string _label)
 239     : PacketQueue(_em, _label), masterPort(_masterPort)
 240 {
 241 }
 242
 243 bool
 244 ReqPacketQueue::sendTiming(PacketPtr pkt)
 245 {
 246     return masterPort.sendTimingReq(pkt);
 247 }
 248
 249 SnoopRespPacketQueue::SnoopRespPacketQueue(EventManager& _em,
 250                                            MasterPort& _masterPort,
 251                                            const std::string _label)
 252     : PacketQueue(_em, _label), masterPort(_masterPort)
 253 {
 254 }
 255
 256 bool
 257 SnoopRespPacketQueue::sendTiming(PacketPtr pkt)
 258 {
 259     return masterPort.sendTimingSnoopResp(pkt);
 260 }
 261
 262 RespPacketQueue::RespPacketQueue(EventManager& _em, SlavePort& _slavePort,
 263                                  const std::string _label)
 264     : PacketQueue(_em, _label), slavePort(_slavePort)
 265 {
 266 }
 267
 268 bool
 269 RespPacketQueue::sendTiming(PacketPtr pkt)
 270 {
 271     return slavePort.sendTimingResp(pkt);
 272 }