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47 * Definition of a crossbar object.
50 #include "mem/xbar.hh"
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"
58 BaseXBar::BaseXBar(const BaseXBarParams
*p
)
60 frontendLatency(p
->frontend_latency
),
61 forwardLatency(p
->forward_latency
),
62 responseLatency(p
->response_latency
),
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
),
69 transDist(this, "trans_dist", "Transaction distribution"),
70 pktCount(this, "pkt_count",
71 "Packet count per connected master and slave (bytes)"),
72 pktSize(this, "pkt_size",
73 "Cumulative packet size per connected master and slave (bytes)")
79 for (auto m
: masterPorts
)
82 for (auto s
: slavePorts
)
87 BaseXBar::getPort(const std::string
&if_name
, PortID idx
)
89 if (if_name
== "master" && idx
< masterPorts
.size()) {
90 // the master port index translates directly to the vector position
91 return *masterPorts
[idx
];
92 } else if (if_name
== "default") {
93 return *masterPorts
[defaultPortID
];
94 } else if (if_name
== "slave" && idx
< slavePorts
.size()) {
95 // the slave port index translates directly to the vector position
96 return *slavePorts
[idx
];
98 return ClockedObject::getPort(if_name
, idx
);
103 BaseXBar::calcPacketTiming(PacketPtr pkt
, Tick header_delay
)
105 // the crossbar will be called at a time that is not necessarily
106 // coinciding with its own clock, so start by determining how long
107 // until the next clock edge (could be zero)
108 Tick offset
= clockEdge() - curTick();
110 // the header delay depends on the path through the crossbar, and
111 // we therefore rely on the caller to provide the actual
113 pkt
->headerDelay
+= offset
+ header_delay
;
115 // note that we add the header delay to the existing value, and
116 // align it to the crossbar clock
118 // do a quick sanity check to ensure the timings are not being
119 // ignored, note that this specific value may cause problems for
120 // slower interconnects
121 panic_if(pkt
->headerDelay
> SimClock::Int::us
,
122 "Encountered header delay exceeding 1 us\n");
124 if (pkt
->hasData()) {
125 // the payloadDelay takes into account the relative time to
126 // deliver the payload of the packet, after the header delay,
127 // we take the maximum since the payload delay could already
128 // be longer than what this parcitular crossbar enforces.
129 pkt
->payloadDelay
= std::max
<Tick
>(pkt
->payloadDelay
,
130 divCeil(pkt
->getSize(), width
) *
134 // the payload delay is not paying for the clock offset as that is
135 // already done using the header delay, and the payload delay is
136 // also used to determine how long the crossbar layer is busy and
137 // thus regulates throughput
140 template <typename SrcType
, typename DstType
>
141 BaseXBar::Layer
<SrcType
, DstType
>::Layer(DstType
& _port
, BaseXBar
& _xbar
,
142 const std::string
& _name
) :
143 Stats::Group(&_xbar
, _name
.c_str()),
144 port(_port
), xbar(_xbar
), _name(xbar
.name() + "." + _name
), state(IDLE
),
145 waitingForPeer(NULL
), releaseEvent([this]{ releaseLayer(); }, name()),
146 ADD_STAT(occupancy
, "Layer occupancy (ticks)"),
147 ADD_STAT(utilization
, "Layer utilization (%)")
150 .flags(Stats::nozero
);
154 .flags(Stats::nozero
);
156 utilization
= 100 * occupancy
/ simTicks
;
159 template <typename SrcType
, typename DstType
>
160 void BaseXBar::Layer
<SrcType
, DstType
>::occupyLayer(Tick until
)
162 // ensure the state is busy at this point, as the layer should
163 // transition from idle as soon as it has decided to forward the
164 // packet to prevent any follow-on calls to sendTiming seeing an
166 assert(state
== BUSY
);
168 // until should never be 0 as express snoops never occupy the layer
170 xbar
.schedule(releaseEvent
, until
);
172 // account for the occupied ticks
173 occupancy
+= until
- curTick();
175 DPRINTF(BaseXBar
, "The crossbar layer is now busy from tick %d to %d\n",
179 template <typename SrcType
, typename DstType
>
181 BaseXBar::Layer
<SrcType
, DstType
>::tryTiming(SrcType
* src_port
)
183 // if we are in the retry state, we will not see anything but the
184 // retrying port (or in the case of the snoop ports the snoop
185 // response port that mirrors the actual slave port) as we leave
186 // this state again in zero time if the peer does not immediately
187 // call the layer when receiving the retry
189 // first we see if the layer is busy, next we check if the
190 // destination port is already engaged in a transaction waiting
191 // for a retry from the peer
192 if (state
== BUSY
|| waitingForPeer
!= NULL
) {
193 // the port should not be waiting already
194 assert(std::find(waitingForLayer
.begin(), waitingForLayer
.end(),
195 src_port
) == waitingForLayer
.end());
197 // put the port at the end of the retry list waiting for the
198 // layer to be freed up (and in the case of a busy peer, for
199 // that transaction to go through, and then the layer to free
201 waitingForLayer
.push_back(src_port
);
210 template <typename SrcType
, typename DstType
>
212 BaseXBar::Layer
<SrcType
, DstType
>::succeededTiming(Tick busy_time
)
214 // we should have gone from idle or retry to busy in the tryTiming
216 assert(state
== BUSY
);
218 // occupy the layer accordingly
219 occupyLayer(busy_time
);
222 template <typename SrcType
, typename DstType
>
224 BaseXBar::Layer
<SrcType
, DstType
>::failedTiming(SrcType
* src_port
,
227 // ensure no one got in between and tried to send something to
229 assert(waitingForPeer
== NULL
);
231 // if the source port is the current retrying one or not, we have
232 // failed in forwarding and should track that we are now waiting
233 // for the peer to send a retry
234 waitingForPeer
= src_port
;
236 // we should have gone from idle or retry to busy in the tryTiming
238 assert(state
== BUSY
);
240 // occupy the bus accordingly
241 occupyLayer(busy_time
);
244 template <typename SrcType
, typename DstType
>
246 BaseXBar::Layer
<SrcType
, DstType
>::releaseLayer()
248 // releasing the bus means we should now be idle
249 assert(state
== BUSY
);
250 assert(!releaseEvent
.scheduled());
255 // bus layer is now idle, so if someone is waiting we can retry
256 if (!waitingForLayer
.empty()) {
257 // there is no point in sending a retry if someone is still
258 // waiting for the peer
259 if (waitingForPeer
== NULL
)
261 } else if (waitingForPeer
== NULL
&& drainState() == DrainState::Draining
) {
262 DPRINTF(Drain
, "Crossbar done draining, signaling drain manager\n");
263 //If we weren't able to drain before, do it now.
268 template <typename SrcType
, typename DstType
>
270 BaseXBar::Layer
<SrcType
, DstType
>::retryWaiting()
272 // this should never be called with no one waiting
273 assert(!waitingForLayer
.empty());
275 // we always go to retrying from idle
276 assert(state
== IDLE
);
281 // set the retrying port to the front of the retry list and pop it
283 SrcType
* retryingPort
= waitingForLayer
.front();
284 waitingForLayer
.pop_front();
286 // tell the port to retry, which in some cases ends up calling the
288 sendRetry(retryingPort
);
290 // If the layer is still in the retry state, sendTiming wasn't
291 // called in zero time (e.g. the cache does this when a writeback
293 if (state
== RETRY
) {
294 // update the state to busy and reset the retrying port, we
295 // have done our bit and sent the retry
298 // occupy the crossbar layer until the next clock edge
299 occupyLayer(xbar
.clockEdge());
303 template <typename SrcType
, typename DstType
>
305 BaseXBar::Layer
<SrcType
, DstType
>::recvRetry()
307 // we should never get a retry without having failed to forward
308 // something to this port
309 assert(waitingForPeer
!= NULL
);
311 // add the port where the failed packet originated to the front of
312 // the waiting ports for the layer, this allows us to call retry
313 // on the port immediately if the crossbar layer is idle
314 waitingForLayer
.push_front(waitingForPeer
);
316 // we are no longer waiting for the peer
317 waitingForPeer
= NULL
;
319 // if the layer is idle, retry this port straight away, if we
320 // are busy, then simply let the port wait for its turn
324 assert(state
== BUSY
);
329 BaseXBar::findPort(AddrRange addr_range
)
331 // we should never see any address lookups before we've got the
332 // ranges of all connected slave modules
333 assert(gotAllAddrRanges
);
335 // Check the address map interval tree
336 auto i
= portMap
.contains(addr_range
);
337 if (i
!= portMap
.end()) {
341 // Check if this matches the default range
342 if (useDefaultRange
) {
343 if (addr_range
.isSubset(defaultRange
)) {
344 DPRINTF(AddrRanges
, " found addr %s on default\n",
345 addr_range
.to_string());
346 return defaultPortID
;
348 } else if (defaultPortID
!= InvalidPortID
) {
349 DPRINTF(AddrRanges
, "Unable to find destination for %s, "
350 "will use default port\n", addr_range
.to_string());
351 return defaultPortID
;
354 // we should use the range for the default port and it did not
355 // match, or the default port is not set
356 fatal("Unable to find destination for %s on %s\n", addr_range
.to_string(),
360 /** Function called by the port when the crossbar is receiving a range change.*/
362 BaseXBar::recvRangeChange(PortID master_port_id
)
364 DPRINTF(AddrRanges
, "Received range change from slave port %s\n",
365 masterPorts
[master_port_id
]->getPeer());
367 // remember that we got a range from this master port and thus the
368 // connected slave module
369 gotAddrRanges
[master_port_id
] = true;
371 // update the global flag
372 if (!gotAllAddrRanges
) {
373 // take a logical AND of all the ports and see if we got
374 // ranges from everyone
375 gotAllAddrRanges
= true;
376 std::vector
<bool>::const_iterator r
= gotAddrRanges
.begin();
377 while (gotAllAddrRanges
&& r
!= gotAddrRanges
.end()) {
378 gotAllAddrRanges
&= *r
++;
380 if (gotAllAddrRanges
)
381 DPRINTF(AddrRanges
, "Got address ranges from all slaves\n");
384 // note that we could get the range from the default port at any
385 // point in time, and we cannot assume that the default range is
386 // set before the other ones are, so we do additional checks once
387 // all ranges are provided
388 if (master_port_id
== defaultPortID
) {
389 // only update if we are indeed checking ranges for the
390 // default port since the port might not have a valid range
392 if (useDefaultRange
) {
393 AddrRangeList ranges
= masterPorts
[master_port_id
]->getAddrRanges();
395 if (ranges
.size() != 1)
396 fatal("Crossbar %s may only have a single default range",
399 defaultRange
= ranges
.front();
402 // the ports are allowed to update their address ranges
403 // dynamically, so remove any existing entries
404 if (gotAddrRanges
[master_port_id
]) {
405 for (auto p
= portMap
.begin(); p
!= portMap
.end(); ) {
406 if (p
->second
== master_port_id
)
407 // erasing invalidates the iterator, so advance it
408 // before the deletion takes place
415 AddrRangeList ranges
= masterPorts
[master_port_id
]->getAddrRanges();
417 for (const auto& r
: ranges
) {
418 DPRINTF(AddrRanges
, "Adding range %s for id %d\n",
419 r
.to_string(), master_port_id
);
420 if (portMap
.insert(r
, master_port_id
) == portMap
.end()) {
421 PortID conflict_id
= portMap
.intersects(r
)->second
;
422 fatal("%s has two ports responding within range "
426 masterPorts
[master_port_id
]->getPeer(),
427 masterPorts
[conflict_id
]->getPeer());
432 // if we have received ranges from all our neighbouring slave
433 // modules, go ahead and tell our connected master modules in
434 // turn, this effectively assumes a tree structure of the system
435 if (gotAllAddrRanges
) {
436 DPRINTF(AddrRanges
, "Aggregating address ranges\n");
439 // start out with the default range
440 if (useDefaultRange
) {
441 if (!gotAddrRanges
[defaultPortID
])
442 fatal("Crossbar %s uses default range, but none provided",
445 xbarRanges
.push_back(defaultRange
);
446 DPRINTF(AddrRanges
, "-- Adding default %s\n",
447 defaultRange
.to_string());
450 // merge all interleaved ranges and add any range that is not
451 // a subset of the default range
452 std::vector
<AddrRange
> intlv_ranges
;
453 for (const auto& r
: portMap
) {
454 // if the range is interleaved then save it for now
455 if (r
.first
.interleaved()) {
456 // if we already got interleaved ranges that are not
457 // part of the same range, then first do a merge
458 // before we add the new one
459 if (!intlv_ranges
.empty() &&
460 !intlv_ranges
.back().mergesWith(r
.first
)) {
461 DPRINTF(AddrRanges
, "-- Merging range from %d ranges\n",
462 intlv_ranges
.size());
463 AddrRange
merged_range(intlv_ranges
);
464 // next decide if we keep the merged range or not
465 if (!(useDefaultRange
&&
466 merged_range
.isSubset(defaultRange
))) {
467 xbarRanges
.push_back(merged_range
);
468 DPRINTF(AddrRanges
, "-- Adding merged range %s\n",
469 merged_range
.to_string());
471 intlv_ranges
.clear();
473 intlv_ranges
.push_back(r
.first
);
475 // keep the current range if not a subset of the default
476 if (!(useDefaultRange
&&
477 r
.first
.isSubset(defaultRange
))) {
478 xbarRanges
.push_back(r
.first
);
479 DPRINTF(AddrRanges
, "-- Adding range %s\n",
480 r
.first
.to_string());
485 // if there is still interleaved ranges waiting to be merged,
486 // go ahead and do it
487 if (!intlv_ranges
.empty()) {
488 DPRINTF(AddrRanges
, "-- Merging range from %d ranges\n",
489 intlv_ranges
.size());
490 AddrRange
merged_range(intlv_ranges
);
491 if (!(useDefaultRange
&& merged_range
.isSubset(defaultRange
))) {
492 xbarRanges
.push_back(merged_range
);
493 DPRINTF(AddrRanges
, "-- Adding merged range %s\n",
494 merged_range
.to_string());
498 // also check that no range partially intersects with the
499 // default range, this has to be done after all ranges are set
500 // as there are no guarantees for when the default range is
501 // update with respect to the other ones
502 if (useDefaultRange
) {
503 for (const auto& r
: xbarRanges
) {
504 // see if the new range is partially
505 // overlapping the default range
506 if (r
.intersects(defaultRange
) &&
507 !r
.isSubset(defaultRange
))
508 fatal("Range %s intersects the " \
509 "default range of %s but is not a " \
510 "subset\n", r
.to_string(), name());
514 // tell all our neighbouring master ports that our address
515 // ranges have changed
516 for (const auto& s
: slavePorts
)
517 s
->sendRangeChange();
522 BaseXBar::getAddrRanges() const
524 // we should never be asked without first having sent a range
525 // change, and the latter is only done once we have all the ranges
526 // of the connected devices
527 assert(gotAllAddrRanges
);
529 // at the moment, this never happens, as there are no cycles in
530 // the range queries and no devices on the master side of a crossbar
531 // (CPU, cache, bridge etc) actually care about the ranges of the
532 // ports they are connected to
534 DPRINTF(AddrRanges
, "Received address range request\n");
542 ClockedObject::regStats();
544 using namespace Stats
;
547 .init(MemCmd::NUM_MEM_CMDS
)
550 // get the string representation of the commands
551 for (int i
= 0; i
< MemCmd::NUM_MEM_CMDS
; i
++) {
553 const std::string
&cstr
= cmd
.toString();
554 transDist
.subname(i
, cstr
);
558 .init(slavePorts
.size(), masterPorts
.size())
559 .flags(total
| nozero
| nonan
);
562 .init(slavePorts
.size(), masterPorts
.size())
563 .flags(total
| nozero
| nonan
);
565 // both the packet count and total size are two-dimensional
566 // vectors, indexed by slave port id and master port id, thus the
567 // neighbouring master and slave, they do not differentiate what
568 // came from the master and was forwarded to the slave (requests
569 // and snoop responses) and what came from the slave and was
570 // forwarded to the master (responses and snoop requests)
571 for (int i
= 0; i
< slavePorts
.size(); i
++) {
572 pktCount
.subname(i
, slavePorts
[i
]->getPeer().name());
573 pktSize
.subname(i
, slavePorts
[i
]->getPeer().name());
574 for (int j
= 0; j
< masterPorts
.size(); j
++) {
575 pktCount
.ysubname(j
, masterPorts
[j
]->getPeer().name());
576 pktSize
.ysubname(j
, masterPorts
[j
]->getPeer().name());
581 template <typename SrcType
, typename DstType
>
583 BaseXBar::Layer
<SrcType
, DstType
>::drain()
585 //We should check that we're not "doing" anything, and that noone is
586 //waiting. We might be idle but have someone waiting if the device we
587 //contacted for a retry didn't actually retry.
589 DPRINTF(Drain
, "Crossbar not drained\n");
590 return DrainState::Draining
;
592 return DrainState::Drained
;
597 * Crossbar layer template instantiations. Could be removed with _impl.hh
598 * file, but since there are only two given options (MasterPort and
599 * SlavePort) it seems a bit excessive at this point.
601 template class BaseXBar::Layer
<SlavePort
, MasterPort
>;
602 template class BaseXBar::Layer
<MasterPort
, SlavePort
>;