src/mem/packet_queue.cc

   1 /*
   2  * Copyright (c) 2012 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     : em(_em), sendEvent(this), drainManager(NULL), label(_label),
  53       waitingOnRetry(false)
  54 {
  55 }
  56
  57 PacketQueue::~PacketQueue()
  58 {
  59 }
  60
  61 void
  62 PacketQueue::retry()
  63 {
  64     DPRINTF(PacketQueue, "Queue %s received retry\n", name());
  65     assert(waitingOnRetry);
  66     sendDeferredPacket();
  67 }
  68
  69 bool
  70 PacketQueue::checkFunctional(PacketPtr pkt)
  71 {
  72     pkt->pushLabel(label);
  73
  74     auto i = transmitList.begin();
  75     bool found = false;
  76
  77     while (!found && i != transmitList.end()) {
  78         // If the buffered packet contains data, and it overlaps the
  79         // current packet, then update data
  80         found = pkt->checkFunctional(i->pkt);
  81         ++i;
  82     }
  83
  84     pkt->popLabel();
  85
  86     return found;
  87 }
  88
  89 void
  90 PacketQueue::schedSendEvent(Tick when)
  91 {
  92     // if we are waiting on a retry, do not schedule a send event, and
  93     // instead rely on retry being called
  94     if (waitingOnRetry) {
  95         assert(!sendEvent.scheduled());
  96         return;
  97     }
  98
  99     if (!sendEvent.scheduled()) {
 100         em.schedule(&sendEvent, when);
 101     } else if (sendEvent.when() > when) {
 102         em.reschedule(&sendEvent, when);
 103     }
 104 }
 105
 106 void
 107 PacketQueue::schedSendTiming(PacketPtr pkt, Tick when, bool send_as_snoop)
 108 {
 109     DPRINTF(PacketQueue, "%s for %s address %x size %d\n", __func__,
 110             pkt->cmdString(), pkt->getAddr(), pkt->getSize());
 111     // we can still send a packet before the end of this tick
 112     assert(when >= curTick());
 113
 114     // express snoops should never be queued
 115     assert(!pkt->isExpressSnoop());
 116
 117     // add a very basic sanity check on the port to ensure the
 118     // invisible buffer is not growing beyond reasonable limits
 119     if (transmitList.size() > 100) {
 120         panic("Packet queue %s has grown beyond 100 packets\n",
 121               name());
 122     }
 123
 124     // nothing on the list, or earlier than current front element,
 125     // schedule an event
 126     if (transmitList.empty() || when < transmitList.front().tick) {
 127         // note that currently we ignore a potentially outstanding retry
 128         // and could in theory put a new packet at the head of the
 129         // transmit list before retrying the existing packet
 130         transmitList.push_front(DeferredPacket(when, pkt, send_as_snoop));
 131         schedSendEvent(when);
 132         return;
 133     }
 134
 135     // list is non-empty and this belongs at the end
 136     if (when >= transmitList.back().tick) {
 137         transmitList.push_back(DeferredPacket(when, pkt, send_as_snoop));
 138         return;
 139     }
 140
 141     // this belongs in the middle somewhere, insertion sort
 142     auto i = transmitList.begin();
 143     ++i; // already checked for insertion at front
 144     while (i != transmitList.end() && when >= i->tick)
 145         ++i;
 146     transmitList.insert(i, DeferredPacket(when, pkt, send_as_snoop));
 147 }
 148
 149 void PacketQueue::trySendTiming()
 150 {
 151     assert(deferredPacketReady());
 152
 153     DeferredPacket dp = transmitList.front();
 154
 155     // use the appropriate implementation of sendTiming based on the
 156     // type of port associated with the queue, and whether the packet
 157     // is to be sent as a snoop or not
 158     waitingOnRetry = !sendTiming(dp.pkt, dp.sendAsSnoop);
 159
 160     if (!waitingOnRetry) {
 161         // take the packet off the list
 162         transmitList.pop_front();
 163     }
 164 }
 165
 166 void
 167 PacketQueue::scheduleSend(Tick time)
 168 {
 169     // the next ready time is either determined by the next deferred packet,
 170     // or in the cache through the MSHR ready time
 171     Tick nextReady = std::max(std::min(deferredPacketReadyTime(), time),
 172                               curTick() + 1);
 173
 174     if (nextReady != MaxTick) {
 175         // if the sendTiming caused someone else to call our
 176         // recvTiming we could already have an event scheduled, check
 177         if (!sendEvent.scheduled()) {
 178             em.schedule(&sendEvent, nextReady);
 179         } else if (nextReady < sendEvent.when()) {
 180             // if the new time is earlier than when the event
 181             // currently is scheduled, move it forward
 182             em.reschedule(&sendEvent, nextReady);
 183         }
 184     } else {
 185         // no more to send, so if we're draining, we may be done
 186         if (drainManager && transmitList.empty() && !sendEvent.scheduled()) {
 187             DPRINTF(Drain, "PacketQueue done draining,"
 188                     "processing drain event\n");
 189             drainManager->signalDrainDone();
 190             drainManager = NULL;
 191         }
 192     }
 193 }
 194
 195 void
 196 PacketQueue::sendDeferredPacket()
 197 {
 198     // try to send what is on the list, this will set waitingOnRetry
 199     // accordingly
 200     trySendTiming();
 201
 202     // if we succeeded and are not waiting for a retry, schedule the
 203     // next send
 204     if (!waitingOnRetry) {
 205         scheduleSend();
 206     }
 207 }
 208
 209 void
 210 PacketQueue::processSendEvent()
 211 {
 212     assert(!waitingOnRetry);
 213     sendDeferredPacket();
 214 }
 215
 216 unsigned int
 217 PacketQueue::drain(DrainManager *dm)
 218 {
 219     if (transmitList.empty())
 220         return 0;
 221     DPRINTF(Drain, "PacketQueue not drained\n");
 222     drainManager = dm;
 223     return 1;
 224 }
 225
 226 MasterPacketQueue::MasterPacketQueue(EventManager& _em, MasterPort& _masterPort,
 227                                      const std::string _label)
 228     : PacketQueue(_em, _label), masterPort(_masterPort)
 229 {
 230 }
 231
 232 bool
 233 MasterPacketQueue::sendTiming(PacketPtr pkt, bool send_as_snoop)
 234 {
 235     // attempt to send the packet and return according to the outcome
 236     if (!send_as_snoop)
 237         return masterPort.sendTimingReq(pkt);
 238     else
 239         return masterPort.sendTimingSnoopResp(pkt);
 240 }
 241
 242 SlavePacketQueue::SlavePacketQueue(EventManager& _em, SlavePort& _slavePort,
 243                                    const std::string _label)
 244     : PacketQueue(_em, _label), slavePort(_slavePort)
 245 {
 246 }
 247
 248 bool
 249 SlavePacketQueue::sendTiming(PacketPtr pkt, bool send_as_snoop)
 250 {
 251     // we should never have queued snoop requests
 252     assert(!send_as_snoop);
 253     return slavePort.sendTimingResp(pkt);
 254 }