xbar.cc revision 13808:0a44fbc3a853
1/*
2 * Copyright (c) 2011-2015, 2018 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 *          William Wang
43 */
44
45/**
46 * @file
47 * Definition of a crossbar object.
48 */
49
50#include "mem/xbar.hh"
51
52#include "base/logging.hh"
53#include "base/trace.hh"
54#include "debug/AddrRanges.hh"
55#include "debug/Drain.hh"
56#include "debug/XBar.hh"
57
58BaseXBar::BaseXBar(const BaseXBarParams *p)
59    : MemObject(p),
60      frontendLatency(p->frontend_latency),
61      forwardLatency(p->forward_latency),
62      responseLatency(p->response_latency),
63      width(p->width),
64      gotAddrRanges(p->port_default_connection_count +
65                          p->port_master_connection_count, false),
66      gotAllAddrRanges(false), defaultPortID(InvalidPortID),
67      useDefaultRange(p->use_default_range)
68{}
69
70BaseXBar::~BaseXBar()
71{
72    for (auto m: masterPorts)
73        delete m;
74
75    for (auto s: slavePorts)
76        delete s;
77}
78
79Port &
80BaseXBar::getPort(const std::string &if_name, PortID idx)
81{
82    if (if_name == "master" && idx < masterPorts.size()) {
83        // the master port index translates directly to the vector position
84        return *masterPorts[idx];
85    } else  if (if_name == "default") {
86        return *masterPorts[defaultPortID];
87    } else if (if_name == "slave" && idx < slavePorts.size()) {
88        // the slave port index translates directly to the vector position
89        return *slavePorts[idx];
90    } else {
91        return MemObject::getPort(if_name, idx);
92    }
93}
94
95void
96BaseXBar::calcPacketTiming(PacketPtr pkt, Tick header_delay)
97{
98    // the crossbar will be called at a time that is not necessarily
99    // coinciding with its own clock, so start by determining how long
100    // until the next clock edge (could be zero)
101    Tick offset = clockEdge() - curTick();
102
103    // the header delay depends on the path through the crossbar, and
104    // we therefore rely on the caller to provide the actual
105    // value
106    pkt->headerDelay += offset + header_delay;
107
108    // note that we add the header delay to the existing value, and
109    // align it to the crossbar clock
110
111    // do a quick sanity check to ensure the timings are not being
112    // ignored, note that this specific value may cause problems for
113    // slower interconnects
114    panic_if(pkt->headerDelay > SimClock::Int::us,
115             "Encountered header delay exceeding 1 us\n");
116
117    if (pkt->hasData()) {
118        // the payloadDelay takes into account the relative time to
119        // deliver the payload of the packet, after the header delay,
120        // we take the maximum since the payload delay could already
121        // be longer than what this parcitular crossbar enforces.
122        pkt->payloadDelay = std::max<Tick>(pkt->payloadDelay,
123                                           divCeil(pkt->getSize(), width) *
124                                           clockPeriod());
125    }
126
127    // the payload delay is not paying for the clock offset as that is
128    // already done using the header delay, and the payload delay is
129    // also used to determine how long the crossbar layer is busy and
130    // thus regulates throughput
131}
132
133template <typename SrcType, typename DstType>
134BaseXBar::Layer<SrcType, DstType>::Layer(DstType& _port, BaseXBar& _xbar,
135                                       const std::string& _name) :
136    port(_port), xbar(_xbar), _name(_name), state(IDLE),
137    waitingForPeer(NULL), releaseEvent([this]{ releaseLayer(); }, name())
138{
139}
140
141template <typename SrcType, typename DstType>
142void BaseXBar::Layer<SrcType, DstType>::occupyLayer(Tick until)
143{
144    // ensure the state is busy at this point, as the layer should
145    // transition from idle as soon as it has decided to forward the
146    // packet to prevent any follow-on calls to sendTiming seeing an
147    // unoccupied layer
148    assert(state == BUSY);
149
150    // until should never be 0 as express snoops never occupy the layer
151    assert(until != 0);
152    xbar.schedule(releaseEvent, until);
153
154    // account for the occupied ticks
155    occupancy += until - curTick();
156
157    DPRINTF(BaseXBar, "The crossbar layer is now busy from tick %d to %d\n",
158            curTick(), until);
159}
160
161template <typename SrcType, typename DstType>
162bool
163BaseXBar::Layer<SrcType, DstType>::tryTiming(SrcType* src_port)
164{
165    // if we are in the retry state, we will not see anything but the
166    // retrying port (or in the case of the snoop ports the snoop
167    // response port that mirrors the actual slave port) as we leave
168    // this state again in zero time if the peer does not immediately
169    // call the layer when receiving the retry
170
171    // first we see if the layer is busy, next we check if the
172    // destination port is already engaged in a transaction waiting
173    // for a retry from the peer
174    if (state == BUSY || waitingForPeer != NULL) {
175        // the port should not be waiting already
176        assert(std::find(waitingForLayer.begin(), waitingForLayer.end(),
177                         src_port) == waitingForLayer.end());
178
179        // put the port at the end of the retry list waiting for the
180        // layer to be freed up (and in the case of a busy peer, for
181        // that transaction to go through, and then the layer to free
182        // up)
183        waitingForLayer.push_back(src_port);
184        return false;
185    }
186
187    state = BUSY;
188
189    return true;
190}
191
192template <typename SrcType, typename DstType>
193void
194BaseXBar::Layer<SrcType, DstType>::succeededTiming(Tick busy_time)
195{
196    // we should have gone from idle or retry to busy in the tryTiming
197    // test
198    assert(state == BUSY);
199
200    // occupy the layer accordingly
201    occupyLayer(busy_time);
202}
203
204template <typename SrcType, typename DstType>
205void
206BaseXBar::Layer<SrcType, DstType>::failedTiming(SrcType* src_port,
207                                              Tick busy_time)
208{
209    // ensure no one got in between and tried to send something to
210    // this port
211    assert(waitingForPeer == NULL);
212
213    // if the source port is the current retrying one or not, we have
214    // failed in forwarding and should track that we are now waiting
215    // for the peer to send a retry
216    waitingForPeer = src_port;
217
218    // we should have gone from idle or retry to busy in the tryTiming
219    // test
220    assert(state == BUSY);
221
222    // occupy the bus accordingly
223    occupyLayer(busy_time);
224}
225
226template <typename SrcType, typename DstType>
227void
228BaseXBar::Layer<SrcType, DstType>::releaseLayer()
229{
230    // releasing the bus means we should now be idle
231    assert(state == BUSY);
232    assert(!releaseEvent.scheduled());
233
234    // update the state
235    state = IDLE;
236
237    // bus layer is now idle, so if someone is waiting we can retry
238    if (!waitingForLayer.empty()) {
239        // there is no point in sending a retry if someone is still
240        // waiting for the peer
241        if (waitingForPeer == NULL)
242            retryWaiting();
243    } else if (waitingForPeer == NULL && drainState() == DrainState::Draining) {
244        DPRINTF(Drain, "Crossbar done draining, signaling drain manager\n");
245        //If we weren't able to drain before, do it now.
246        signalDrainDone();
247    }
248}
249
250template <typename SrcType, typename DstType>
251void
252BaseXBar::Layer<SrcType, DstType>::retryWaiting()
253{
254    // this should never be called with no one waiting
255    assert(!waitingForLayer.empty());
256
257    // we always go to retrying from idle
258    assert(state == IDLE);
259
260    // update the state
261    state = RETRY;
262
263    // set the retrying port to the front of the retry list and pop it
264    // off the list
265    SrcType* retryingPort = waitingForLayer.front();
266    waitingForLayer.pop_front();
267
268    // tell the port to retry, which in some cases ends up calling the
269    // layer again
270    sendRetry(retryingPort);
271
272    // If the layer is still in the retry state, sendTiming wasn't
273    // called in zero time (e.g. the cache does this when a writeback
274    // is squashed)
275    if (state == RETRY) {
276        // update the state to busy and reset the retrying port, we
277        // have done our bit and sent the retry
278        state = BUSY;
279
280        // occupy the crossbar layer until the next clock edge
281        occupyLayer(xbar.clockEdge());
282    }
283}
284
285template <typename SrcType, typename DstType>
286void
287BaseXBar::Layer<SrcType, DstType>::recvRetry()
288{
289    // we should never get a retry without having failed to forward
290    // something to this port
291    assert(waitingForPeer != NULL);
292
293    // add the port where the failed packet originated to the front of
294    // the waiting ports for the layer, this allows us to call retry
295    // on the port immediately if the crossbar layer is idle
296    waitingForLayer.push_front(waitingForPeer);
297
298    // we are no longer waiting for the peer
299    waitingForPeer = NULL;
300
301    // if the layer is idle, retry this port straight away, if we
302    // are busy, then simply let the port wait for its turn
303    if (state == IDLE) {
304        retryWaiting();
305    } else {
306        assert(state == BUSY);
307    }
308}
309
310PortID
311BaseXBar::findPort(AddrRange addr_range)
312{
313    // we should never see any address lookups before we've got the
314    // ranges of all connected slave modules
315    assert(gotAllAddrRanges);
316
317    // Check the address map interval tree
318    auto i = portMap.contains(addr_range);
319    if (i != portMap.end()) {
320        return i->second;
321    }
322
323    // Check if this matches the default range
324    if (useDefaultRange) {
325        if (addr_range.isSubset(defaultRange)) {
326            DPRINTF(AddrRanges, "  found addr %s on default\n",
327                    addr_range.to_string());
328            return defaultPortID;
329        }
330    } else if (defaultPortID != InvalidPortID) {
331        DPRINTF(AddrRanges, "Unable to find destination for %s, "
332                "will use default port\n", addr_range.to_string());
333        return defaultPortID;
334    }
335
336    // we should use the range for the default port and it did not
337    // match, or the default port is not set
338    fatal("Unable to find destination for %s on %s\n", addr_range.to_string(),
339          name());
340}
341
342/** Function called by the port when the crossbar is receiving a range change.*/
343void
344BaseXBar::recvRangeChange(PortID master_port_id)
345{
346    DPRINTF(AddrRanges, "Received range change from slave port %s\n",
347            masterPorts[master_port_id]->getSlavePort().name());
348
349    // remember that we got a range from this master port and thus the
350    // connected slave module
351    gotAddrRanges[master_port_id] = true;
352
353    // update the global flag
354    if (!gotAllAddrRanges) {
355        // take a logical AND of all the ports and see if we got
356        // ranges from everyone
357        gotAllAddrRanges = true;
358        std::vector<bool>::const_iterator r = gotAddrRanges.begin();
359        while (gotAllAddrRanges &&  r != gotAddrRanges.end()) {
360            gotAllAddrRanges &= *r++;
361        }
362        if (gotAllAddrRanges)
363            DPRINTF(AddrRanges, "Got address ranges from all slaves\n");
364    }
365
366    // note that we could get the range from the default port at any
367    // point in time, and we cannot assume that the default range is
368    // set before the other ones are, so we do additional checks once
369    // all ranges are provided
370    if (master_port_id == defaultPortID) {
371        // only update if we are indeed checking ranges for the
372        // default port since the port might not have a valid range
373        // otherwise
374        if (useDefaultRange) {
375            AddrRangeList ranges = masterPorts[master_port_id]->getAddrRanges();
376
377            if (ranges.size() != 1)
378                fatal("Crossbar %s may only have a single default range",
379                      name());
380
381            defaultRange = ranges.front();
382        }
383    } else {
384        // the ports are allowed to update their address ranges
385        // dynamically, so remove any existing entries
386        if (gotAddrRanges[master_port_id]) {
387            for (auto p = portMap.begin(); p != portMap.end(); ) {
388                if (p->second == master_port_id)
389                    // erasing invalidates the iterator, so advance it
390                    // before the deletion takes place
391                    portMap.erase(p++);
392                else
393                    p++;
394            }
395        }
396
397        AddrRangeList ranges = masterPorts[master_port_id]->getAddrRanges();
398
399        for (const auto& r: ranges) {
400            DPRINTF(AddrRanges, "Adding range %s for id %d\n",
401                    r.to_string(), master_port_id);
402            if (portMap.insert(r, master_port_id) == portMap.end()) {
403                PortID conflict_id = portMap.intersects(r)->second;
404                fatal("%s has two ports responding within range "
405                      "%s:\n\t%s\n\t%s\n",
406                      name(),
407                      r.to_string(),
408                      masterPorts[master_port_id]->getSlavePort().name(),
409                      masterPorts[conflict_id]->getSlavePort().name());
410            }
411        }
412    }
413
414    // if we have received ranges from all our neighbouring slave
415    // modules, go ahead and tell our connected master modules in
416    // turn, this effectively assumes a tree structure of the system
417    if (gotAllAddrRanges) {
418        DPRINTF(AddrRanges, "Aggregating address ranges\n");
419        xbarRanges.clear();
420
421        // start out with the default range
422        if (useDefaultRange) {
423            if (!gotAddrRanges[defaultPortID])
424                fatal("Crossbar %s uses default range, but none provided",
425                      name());
426
427            xbarRanges.push_back(defaultRange);
428            DPRINTF(AddrRanges, "-- Adding default %s\n",
429                    defaultRange.to_string());
430        }
431
432        // merge all interleaved ranges and add any range that is not
433        // a subset of the default range
434        std::vector<AddrRange> intlv_ranges;
435        for (const auto& r: portMap) {
436            // if the range is interleaved then save it for now
437            if (r.first.interleaved()) {
438                // if we already got interleaved ranges that are not
439                // part of the same range, then first do a merge
440                // before we add the new one
441                if (!intlv_ranges.empty() &&
442                    !intlv_ranges.back().mergesWith(r.first)) {
443                    DPRINTF(AddrRanges, "-- Merging range from %d ranges\n",
444                            intlv_ranges.size());
445                    AddrRange merged_range(intlv_ranges);
446                    // next decide if we keep the merged range or not
447                    if (!(useDefaultRange &&
448                          merged_range.isSubset(defaultRange))) {
449                        xbarRanges.push_back(merged_range);
450                        DPRINTF(AddrRanges, "-- Adding merged range %s\n",
451                                merged_range.to_string());
452                    }
453                    intlv_ranges.clear();
454                }
455                intlv_ranges.push_back(r.first);
456            } else {
457                // keep the current range if not a subset of the default
458                if (!(useDefaultRange &&
459                      r.first.isSubset(defaultRange))) {
460                    xbarRanges.push_back(r.first);
461                    DPRINTF(AddrRanges, "-- Adding range %s\n",
462                            r.first.to_string());
463                }
464            }
465        }
466
467        // if there is still interleaved ranges waiting to be merged,
468        // go ahead and do it
469        if (!intlv_ranges.empty()) {
470            DPRINTF(AddrRanges, "-- Merging range from %d ranges\n",
471                    intlv_ranges.size());
472            AddrRange merged_range(intlv_ranges);
473            if (!(useDefaultRange && merged_range.isSubset(defaultRange))) {
474                xbarRanges.push_back(merged_range);
475                DPRINTF(AddrRanges, "-- Adding merged range %s\n",
476                        merged_range.to_string());
477            }
478        }
479
480        // also check that no range partially intersects with the
481        // default range, this has to be done after all ranges are set
482        // as there are no guarantees for when the default range is
483        // update with respect to the other ones
484        if (useDefaultRange) {
485            for (const auto& r: xbarRanges) {
486                // see if the new range is partially
487                // overlapping the default range
488                if (r.intersects(defaultRange) &&
489                    !r.isSubset(defaultRange))
490                    fatal("Range %s intersects the "                    \
491                          "default range of %s but is not a "           \
492                          "subset\n", r.to_string(), name());
493            }
494        }
495
496        // tell all our neighbouring master ports that our address
497        // ranges have changed
498        for (const auto& s: slavePorts)
499            s->sendRangeChange();
500    }
501}
502
503AddrRangeList
504BaseXBar::getAddrRanges() const
505{
506    // we should never be asked without first having sent a range
507    // change, and the latter is only done once we have all the ranges
508    // of the connected devices
509    assert(gotAllAddrRanges);
510
511    // at the moment, this never happens, as there are no cycles in
512    // the range queries and no devices on the master side of a crossbar
513    // (CPU, cache, bridge etc) actually care about the ranges of the
514    // ports they are connected to
515
516    DPRINTF(AddrRanges, "Received address range request\n");
517
518    return xbarRanges;
519}
520
521void
522BaseXBar::regStats()
523{
524    ClockedObject::regStats();
525
526    using namespace Stats;
527
528    transDist
529        .init(MemCmd::NUM_MEM_CMDS)
530        .name(name() + ".trans_dist")
531        .desc("Transaction distribution")
532        .flags(nozero);
533
534    // get the string representation of the commands
535    for (int i = 0; i < MemCmd::NUM_MEM_CMDS; i++) {
536        MemCmd cmd(i);
537        const std::string &cstr = cmd.toString();
538        transDist.subname(i, cstr);
539    }
540
541    pktCount
542        .init(slavePorts.size(), masterPorts.size())
543        .name(name() + ".pkt_count")
544        .desc("Packet count per connected master and slave (bytes)")
545        .flags(total | nozero | nonan);
546
547    pktSize
548        .init(slavePorts.size(), masterPorts.size())
549        .name(name() + ".pkt_size")
550        .desc("Cumulative packet size per connected master and slave (bytes)")
551        .flags(total | nozero | nonan);
552
553    // both the packet count and total size are two-dimensional
554    // vectors, indexed by slave port id and master port id, thus the
555    // neighbouring master and slave, they do not differentiate what
556    // came from the master and was forwarded to the slave (requests
557    // and snoop responses) and what came from the slave and was
558    // forwarded to the master (responses and snoop requests)
559    for (int i = 0; i < slavePorts.size(); i++) {
560        pktCount.subname(i, slavePorts[i]->getMasterPort().name());
561        pktSize.subname(i, slavePorts[i]->getMasterPort().name());
562        for (int j = 0; j < masterPorts.size(); j++) {
563            pktCount.ysubname(j, masterPorts[j]->getSlavePort().name());
564            pktSize.ysubname(j, masterPorts[j]->getSlavePort().name());
565        }
566    }
567}
568
569template <typename SrcType, typename DstType>
570DrainState
571BaseXBar::Layer<SrcType, DstType>::drain()
572{
573    //We should check that we're not "doing" anything, and that noone is
574    //waiting. We might be idle but have someone waiting if the device we
575    //contacted for a retry didn't actually retry.
576    if (state != IDLE) {
577        DPRINTF(Drain, "Crossbar not drained\n");
578        return DrainState::Draining;
579    } else {
580        return DrainState::Drained;
581    }
582}
583
584template <typename SrcType, typename DstType>
585void
586BaseXBar::Layer<SrcType, DstType>::regStats()
587{
588    using namespace Stats;
589
590    occupancy
591        .name(name() + ".occupancy")
592        .desc("Layer occupancy (ticks)")
593        .flags(nozero);
594
595    utilization
596        .name(name() + ".utilization")
597        .desc("Layer utilization (%)")
598        .precision(1)
599        .flags(nozero);
600
601    utilization = 100 * occupancy / simTicks;
602}
603
604/**
605 * Crossbar layer template instantiations. Could be removed with _impl.hh
606 * file, but since there are only two given options (MasterPort and
607 * SlavePort) it seems a bit excessive at this point.
608 */
609template class BaseXBar::Layer<SlavePort, MasterPort>;
610template class BaseXBar::Layer<MasterPort, SlavePort>;
611