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