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 "mem/packet_queue.hh"
  45
  46 #include "base/trace.hh"
  47 #include "debug/Drain.hh"
  48 #include "debug/PacketQueue.hh"
  49
  50 using namespace std;
  51
  52 PacketQueue::PacketQueue(EventManager& _em, const std::string& _label,
  53                          const std::string& _sendEventName,
  54                          bool disable_sanity_check)
  55     : em(_em), sendEvent([this]{ processSendEvent(); }, _sendEventName),
  56       _disableSanityCheck(disable_sanity_check),
  57       label(_label), waitingOnRetry(false)
  58 {
  59 }
  60
  61 PacketQueue::~PacketQueue()
  62 {
  63 }
  64
  65 void
  66 PacketQueue::retry()
  67 {
  68     DPRINTF(PacketQueue, "Queue %s received retry\n", name());
  69     assert(waitingOnRetry);
  70     waitingOnRetry = false;
  71     sendDeferredPacket();
  72 }
  73
  74 bool
  75 PacketQueue::hasAddr(Addr addr) const
  76 {
  77     // caller is responsible for ensuring that all packets have the
  78     // same alignment
  79     for (const auto& p : transmitList) {
  80         if (p.pkt->getAddr() == addr)
  81             return true;
  82     }
  83     return false;
  84 }
  85
  86 bool
  87 PacketQueue::checkFunctional(PacketPtr pkt)
  88 {
  89     pkt->pushLabel(label);
  90
  91     auto i = transmitList.begin();
  92     bool found = false;
  93
  94     while (!found && i != transmitList.end()) {
  95         // If the buffered packet contains data, and it overlaps the
  96         // current packet, then update data
  97         found = pkt->checkFunctional(i->pkt);
  98         ++i;
  99     }
 100
 101     pkt->popLabel();
 102
 103     return found;
 104 }
 105
 106 void
 107 PacketQueue::schedSendTiming(PacketPtr pkt, Tick when, bool force_order)
 108 {
 109     DPRINTF(PacketQueue, "%s for %s address %x size %d when %lu ord: %i\n",
 110             __func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize(), when,
 111             force_order);
 112
 113     // we can still send a packet before the end of this tick
 114     assert(when >= curTick());
 115
 116     // express snoops should never be queued
 117     assert(!pkt->isExpressSnoop());
 118
 119     // add a very basic sanity check on the port to ensure the
 120     // invisible buffer is not growing beyond reasonable limits
 121     if (!_disableSanityCheck && transmitList.size() > 100) {
 122         panic("Packet queue %s has grown beyond 100 packets\n",
 123               name());
 124     }
 125
 126     // nothing on the list
 127     if (transmitList.empty()) {
 128         transmitList.emplace_front(when, pkt);
 129         schedSendEvent(when);
 130         return;
 131     }
 132
 133     // we should either have an outstanding retry, or a send event
 134     // scheduled, but there is an unfortunate corner case where the
 135     // x86 page-table walker and timing CPU send out a new request as
 136     // part of the receiving of a response (called by
 137     // PacketQueue::sendDeferredPacket), in which we end up calling
 138     // ourselves again before we had a chance to update waitingOnRetry
 139     // assert(waitingOnRetry || sendEvent.scheduled());
 140
 141     // this belongs in the middle somewhere, so search from the end to
 142     // order by tick; however, if force_order is set, also make sure
 143     // not to re-order in front of some existing packet with the same
 144     // address
 145     auto i = transmitList.end();
 146     --i;
 147     while (i != transmitList.begin() && when < i->tick &&
 148            !(force_order && i->pkt->getAddr() == pkt->getAddr()))
 149         --i;
 150
 151     // emplace inserts the element before the position pointed to by
 152     // the iterator, so advance it one step
 153     transmitList.emplace(++i, when, pkt);
 154 }
 155
 156 void
 157 PacketQueue::schedSendEvent(Tick when)
 158 {
 159     // if we are waiting on a retry just hold off
 160     if (waitingOnRetry) {
 161         DPRINTF(PacketQueue, "Not scheduling send as waiting for retry\n");
 162         assert(!sendEvent.scheduled());
 163         return;
 164     }
 165
 166     if (when != MaxTick) {
 167         // we cannot go back in time, and to be consistent we stick to
 168         // one tick in the future
 169         when = std::max(when, curTick() + 1);
 170         // @todo Revisit the +1
 171
 172         if (!sendEvent.scheduled()) {
 173             em.schedule(&sendEvent, when);
 174         } else if (when < sendEvent.when()) {
 175             // if the new time is earlier than when the event
 176             // currently is scheduled, move it forward
 177             em.reschedule(&sendEvent, when);
 178         }
 179     } else {
 180         // we get a MaxTick when there is no more to send, so if we're
 181         // draining, we may be done at this point
 182         if (drainState() == DrainState::Draining &&
 183             transmitList.empty() && !sendEvent.scheduled()) {
 184
 185             DPRINTF(Drain, "PacketQueue done draining,"
 186                     "processing drain event\n");
 187             signalDrainDone();
 188         }
 189     }
 190 }
 191
 192 void
 193 PacketQueue::sendDeferredPacket()
 194 {
 195     // sanity checks
 196     assert(!waitingOnRetry);
 197     assert(deferredPacketReady());
 198
 199     DeferredPacket dp = transmitList.front();
 200
 201     // take the packet of the list before sending it, as sending of
 202     // the packet in some cases causes a new packet to be enqueued
 203     // (most notaly when responding to the timing CPU, leading to a
 204     // new request hitting in the L1 icache, leading to a new
 205     // response)
 206     transmitList.pop_front();
 207
 208     // use the appropriate implementation of sendTiming based on the
 209     // type of queue
 210     waitingOnRetry = !sendTiming(dp.pkt);
 211
 212     // if we succeeded and are not waiting for a retry, schedule the
 213     // next send
 214     if (!waitingOnRetry) {
 215         schedSendEvent(deferredPacketReadyTime());
 216     } else {
 217         // put the packet back at the front of the list
 218         transmitList.emplace_front(dp);
 219     }
 220 }
 221
 222 void
 223 PacketQueue::processSendEvent()
 224 {
 225     assert(!waitingOnRetry);
 226     sendDeferredPacket();
 227 }
 228
 229 DrainState
 230 PacketQueue::drain()
 231 {
 232     if (transmitList.empty()) {
 233         return DrainState::Drained;
 234     } else {
 235         DPRINTF(Drain, "PacketQueue not drained\n");
 236         return DrainState::Draining;
 237     }
 238 }
 239
 240 ReqPacketQueue::ReqPacketQueue(EventManager& _em, MasterPort& _masterPort,
 241                                const std::string _label)
 242     : PacketQueue(_em, _label, name(_masterPort, _label)),
 243       masterPort(_masterPort)
 244 {
 245 }
 246
 247 bool
 248 ReqPacketQueue::sendTiming(PacketPtr pkt)
 249 {
 250     return masterPort.sendTimingReq(pkt);
 251 }
 252
 253 SnoopRespPacketQueue::SnoopRespPacketQueue(EventManager& _em,
 254                                            MasterPort& _masterPort,
 255                                            const std::string _label)
 256     : PacketQueue(_em, _label, name(_masterPort, _label)),
 257       masterPort(_masterPort)
 258 {
 259 }
 260
 261 bool
 262 SnoopRespPacketQueue::sendTiming(PacketPtr pkt)
 263 {
 264     return masterPort.sendTimingSnoopResp(pkt);
 265 }
 266
 267 RespPacketQueue::RespPacketQueue(EventManager& _em, SlavePort& _slavePort,
 268                                  const std::string _label)
 269     : PacketQueue(_em, _label, name(_slavePort, _label)),
 270       slavePort(_slavePort)
 271 {
 272 }
 273
 274 bool
 275 RespPacketQueue::sendTiming(PacketPtr pkt)
 276 {
 277     return slavePort.sendTimingResp(pkt);
 278 }