packet_queue.cc revision 9663:45df88079f04 
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
49using namespace std;
50
51PacketQueue::PacketQueue(EventManager& _em, const std::string& _label)
52    : em(_em), sendEvent(this), drainManager(NULL), label(_label),
53      waitingOnRetry(false)
54{
55}
56
57PacketQueue::~PacketQueue()
58{
59}
60
61void
62PacketQueue::retry()
63{
64    DPRINTF(PacketQueue, "Queue %s received retry\n", name());
65    assert(waitingOnRetry);
66    sendDeferredPacket();
67}
68
69bool
70PacketQueue::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
90void
91PacketQueue::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
107void
108PacketQueue::schedSendTiming(PacketPtr pkt, Tick when, bool send_as_snoop)
109{
110    DPRINTF(PacketQueue, "%s for %s address %x size %d\n", __func__,
111            pkt->cmdString(), pkt->getAddr(), pkt->getSize());
112    // we can still send a packet before the end of this tick
113    assert(when >= curTick());
114
115    // express snoops should never be queued
116    assert(!pkt->isExpressSnoop());
117
118    // add a very basic sanity check on the port to ensure the
119    // invisible buffer is not growing beyond reasonable limits
120    if (transmitList.size() > 100) {
121        panic("Packet queue %s has grown beyond 100 packets\n",
122              name());
123    }
124
125    // nothing on the list, or earlier than current front element,
126    // schedule an event
127    if (transmitList.empty() || when < transmitList.front().tick) {
128        // note that currently we ignore a potentially outstanding retry
129        // and could in theory put a new packet at the head of the
130        // transmit list before retrying the existing packet
131        transmitList.push_front(DeferredPacket(when, pkt, send_as_snoop));
132        schedSendEvent(when);
133        return;
134    }
135
136    // list is non-empty and this belongs at the end
137    if (when >= transmitList.back().tick) {
138        transmitList.push_back(DeferredPacket(when, pkt, send_as_snoop));
139        return;
140    }
141
142    // this belongs in the middle somewhere, insertion sort
143    DeferredPacketIterator i = transmitList.begin();
144    ++i; // already checked for insertion at front
145    while (i != transmitList.end() && when >= i->tick)
146        ++i;
147    transmitList.insert(i, DeferredPacket(when, pkt, send_as_snoop));
148}
149
150void PacketQueue::trySendTiming()
151{
152    assert(deferredPacketReady());
153
154    // take the next packet off the list here, as we might return to
155    // ourselves through the sendTiming call below
156    DeferredPacket dp = transmitList.front();
157    transmitList.pop_front();
158
159    // use the appropriate implementation of sendTiming based on the
160    // type of port associated with the queue, and whether the packet
161    // is to be sent as a snoop or not
162    waitingOnRetry = !sendTiming(dp.pkt, dp.sendAsSnoop);
163
164    if (waitingOnRetry) {
165        // put the packet back at the front of the list (packet should
166        // not have changed since it wasn't accepted)
167        assert(!sendEvent.scheduled());
168        transmitList.push_front(dp);
169    }
170}
171
172void
173PacketQueue::scheduleSend(Tick time)
174{
175    // the next ready time is either determined by the next deferred packet,
176    // or in the cache through the MSHR ready time
177    Tick nextReady = std::min(deferredPacketReadyTime(), time);
178
179    if (nextReady != MaxTick) {
180        // if the sendTiming caused someone else to call our
181        // recvTiming we could already have an event scheduled, check
182        if (!sendEvent.scheduled())
183            em.schedule(&sendEvent, std::max(nextReady, curTick() + 1));
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
195void
196PacketQueue::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
209void
210PacketQueue::processSendEvent()
211{
212    assert(!waitingOnRetry);
213    sendDeferredPacket();
214}
215
216unsigned int
217PacketQueue::drain(DrainManager *dm)
218{
219    if (transmitList.empty() && !sendEvent.scheduled())
220        return 0;
221    DPRINTF(Drain, "PacketQueue not drained\n");
222    drainManager = dm;
223    return 1;
224}
225
226MasterPacketQueue::MasterPacketQueue(EventManager& _em, MasterPort& _masterPort,
227                                     const std::string _label)
228    : PacketQueue(_em, _label), masterPort(_masterPort)
229{
230}
231
232bool
233MasterPacketQueue::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
242SlavePacketQueue::SlavePacketQueue(EventManager& _em, SlavePort& _slavePort,
243                                   const std::string _label)
244    : PacketQueue(_em, _label), slavePort(_slavePort)
245{
246}
247
248bool
249SlavePacketQueue::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}
255