| /* |
| * Copyright (c) 2011-2019 ARM Limited |
| * All rights reserved |
| * |
| * The license below extends only to copyright in the software and shall |
| * not be construed as granting a license to any other intellectual |
| * property including but not limited to intellectual property relating |
| * to a hardware implementation of the functionality of the software |
| * licensed hereunder. You may use the software subject to the license |
| * terms below provided that you ensure that this notice is replicated |
| * unmodified and in its entirety in all distributions of the software, |
| * modified or unmodified, in source code or in binary form. |
| * |
| * Copyright (c) 2006 The Regents of The University of Michigan |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer; |
| * redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution; |
| * neither the name of the copyright holders nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| * Authors: Ali Saidi |
| * Andreas Hansson |
| * William Wang |
| * Nikos Nikoleris |
| */ |
| |
| /** |
| * @file |
| * Definition of a crossbar object. |
| */ |
| |
| #include "mem/coherent_xbar.hh" |
| |
| #include "base/logging.hh" |
| #include "base/trace.hh" |
| #include "debug/AddrRanges.hh" |
| #include "debug/CoherentXBar.hh" |
| #include "sim/system.hh" |
| |
| CoherentXBar::CoherentXBar(const CoherentXBarParams *p) |
| : BaseXBar(p), system(p->system), snoopFilter(p->snoop_filter), |
| snoopResponseLatency(p->snoop_response_latency), |
| maxOutstandingSnoopCheck(p->max_outstanding_snoops), |
| maxRoutingTableSizeCheck(p->max_routing_table_size), |
| pointOfCoherency(p->point_of_coherency), |
| pointOfUnification(p->point_of_unification) |
| { |
| // create the ports based on the size of the master and slave |
| // vector ports, and the presence of the default port, the ports |
| // are enumerated starting from zero |
| for (int i = 0; i < p->port_master_connection_count; ++i) { |
| std::string portName = csprintf("%s.master[%d]", name(), i); |
| MasterPort* bp = new CoherentXBarMasterPort(portName, *this, i); |
| masterPorts.push_back(bp); |
| reqLayers.push_back(new ReqLayer(*bp, *this, |
| csprintf(".reqLayer%d", i))); |
| snoopLayers.push_back( |
| new SnoopRespLayer(*bp, *this, csprintf(".snoopLayer%d", i))); |
| } |
| |
| // see if we have a default slave device connected and if so add |
| // our corresponding master port |
| if (p->port_default_connection_count) { |
| defaultPortID = masterPorts.size(); |
| std::string portName = name() + ".default"; |
| MasterPort* bp = new CoherentXBarMasterPort(portName, *this, |
| defaultPortID); |
| masterPorts.push_back(bp); |
| reqLayers.push_back(new ReqLayer(*bp, *this, csprintf(".reqLayer%d", |
| defaultPortID))); |
| snoopLayers.push_back(new SnoopRespLayer(*bp, *this, |
| csprintf(".snoopLayer%d", |
| defaultPortID))); |
| } |
| |
| // create the slave ports, once again starting at zero |
| for (int i = 0; i < p->port_slave_connection_count; ++i) { |
| std::string portName = csprintf("%s.slave[%d]", name(), i); |
| QueuedSlavePort* bp = new CoherentXBarSlavePort(portName, *this, i); |
| slavePorts.push_back(bp); |
| respLayers.push_back(new RespLayer(*bp, *this, |
| csprintf(".respLayer%d", i))); |
| snoopRespPorts.push_back(new SnoopRespPort(*bp, *this)); |
| } |
| } |
| |
| CoherentXBar::~CoherentXBar() |
| { |
| for (auto l: reqLayers) |
| delete l; |
| for (auto l: respLayers) |
| delete l; |
| for (auto l: snoopLayers) |
| delete l; |
| for (auto p: snoopRespPorts) |
| delete p; |
| } |
| |
| void |
| CoherentXBar::init() |
| { |
| BaseXBar::init(); |
| |
| // iterate over our slave ports and determine which of our |
| // neighbouring master ports are snooping and add them as snoopers |
| for (const auto& p: slavePorts) { |
| // check if the connected master port is snooping |
| if (p->isSnooping()) { |
| DPRINTF(AddrRanges, "Adding snooping master %s\n", p->getPeer()); |
| snoopPorts.push_back(p); |
| } |
| } |
| |
| if (snoopPorts.empty()) |
| warn("CoherentXBar %s has no snooping ports attached!\n", name()); |
| |
| // inform the snoop filter about the slave ports so it can create |
| // its own internal representation |
| if (snoopFilter) |
| snoopFilter->setSlavePorts(slavePorts); |
| } |
| |
| bool |
| CoherentXBar::recvTimingReq(PacketPtr pkt, PortID slave_port_id) |
| { |
| // determine the source port based on the id |
| SlavePort *src_port = slavePorts[slave_port_id]; |
| |
| // remember if the packet is an express snoop |
| bool is_express_snoop = pkt->isExpressSnoop(); |
| bool cache_responding = pkt->cacheResponding(); |
| // for normal requests, going downstream, the express snoop flag |
| // and the cache responding flag should always be the same |
| assert(is_express_snoop == cache_responding); |
| |
| // determine the destination based on the destination address range |
| PortID master_port_id = findPort(pkt->getAddrRange()); |
| |
| // test if the crossbar should be considered occupied for the current |
| // port, and exclude express snoops from the check |
| if (!is_express_snoop && !reqLayers[master_port_id]->tryTiming(src_port)) { |
| DPRINTF(CoherentXBar, "%s: src %s packet %s BUSY\n", __func__, |
| src_port->name(), pkt->print()); |
| return false; |
| } |
| |
| DPRINTF(CoherentXBar, "%s: src %s packet %s\n", __func__, |
| src_port->name(), pkt->print()); |
| |
| // store size and command as they might be modified when |
| // forwarding the packet |
| unsigned int pkt_size = pkt->hasData() ? pkt->getSize() : 0; |
| unsigned int pkt_cmd = pkt->cmdToIndex(); |
| |
| // store the old header delay so we can restore it if needed |
| Tick old_header_delay = pkt->headerDelay; |
| |
| // a request sees the frontend and forward latency |
| Tick xbar_delay = (frontendLatency + forwardLatency) * clockPeriod(); |
| |
| // set the packet header and payload delay |
| calcPacketTiming(pkt, xbar_delay); |
| |
| // determine how long to be crossbar layer is busy |
| Tick packetFinishTime = clockEdge(Cycles(1)) + pkt->payloadDelay; |
| |
| // is this the destination point for this packet? (e.g. true if |
| // this xbar is the PoC for a cache maintenance operation to the |
| // PoC) otherwise the destination is any cache that can satisfy |
| // the request |
| const bool is_destination = isDestination(pkt); |
| |
| const bool snoop_caches = !system->bypassCaches() && |
| pkt->cmd != MemCmd::WriteClean; |
| if (snoop_caches) { |
| assert(pkt->snoopDelay == 0); |
| |
| if (pkt->isClean() && !is_destination) { |
| // before snooping we need to make sure that the memory |
| // below is not busy and the cache clean request can be |
| // forwarded to it |
| if (!masterPorts[master_port_id]->tryTiming(pkt)) { |
| DPRINTF(CoherentXBar, "%s: src %s packet %s RETRY\n", __func__, |
| src_port->name(), pkt->print()); |
| |
| // update the layer state and schedule an idle event |
| reqLayers[master_port_id]->failedTiming(src_port, |
| clockEdge(Cycles(1))); |
| return false; |
| } |
| } |
| |
| |
| // the packet is a memory-mapped request and should be |
| // broadcasted to our snoopers but the source |
| if (snoopFilter) { |
| // check with the snoop filter where to forward this packet |
| auto sf_res = snoopFilter->lookupRequest(pkt, *src_port); |
| // the time required by a packet to be delivered through |
| // the xbar has to be charged also with to lookup latency |
| // of the snoop filter |
| pkt->headerDelay += sf_res.second * clockPeriod(); |
| DPRINTF(CoherentXBar, "%s: src %s packet %s SF size: %i lat: %i\n", |
| __func__, src_port->name(), pkt->print(), |
| sf_res.first.size(), sf_res.second); |
| |
| if (pkt->isEviction()) { |
| // for block-evicting packets, i.e. writebacks and |
| // clean evictions, there is no need to snoop up, as |
| // all we do is determine if the block is cached or |
| // not, instead just set it here based on the snoop |
| // filter result |
| if (!sf_res.first.empty()) |
| pkt->setBlockCached(); |
| } else { |
| forwardTiming(pkt, slave_port_id, sf_res.first); |
| } |
| } else { |
| forwardTiming(pkt, slave_port_id); |
| } |
| |
| // add the snoop delay to our header delay, and then reset it |
| pkt->headerDelay += pkt->snoopDelay; |
| pkt->snoopDelay = 0; |
| } |
| |
| // set up a sensible starting point |
| bool success = true; |
| |
| // remember if the packet will generate a snoop response by |
| // checking if a cache set the cacheResponding flag during the |
| // snooping above |
| const bool expect_snoop_resp = !cache_responding && pkt->cacheResponding(); |
| bool expect_response = pkt->needsResponse() && !pkt->cacheResponding(); |
| |
| const bool sink_packet = sinkPacket(pkt); |
| |
| // in certain cases the crossbar is responsible for responding |
| bool respond_directly = false; |
| // store the original address as an address mapper could possibly |
| // modify the address upon a sendTimingRequest |
| const Addr addr(pkt->getAddr()); |
| if (sink_packet) { |
| DPRINTF(CoherentXBar, "%s: Not forwarding %s\n", __func__, |
| pkt->print()); |
| } else { |
| // determine if we are forwarding the packet, or responding to |
| // it |
| if (forwardPacket(pkt)) { |
| // if we are passing on, rather than sinking, a packet to |
| // which an upstream cache has committed to responding, |
| // the line was needs writable, and the responding only |
| // had an Owned copy, so we need to immidiately let the |
| // downstream caches know, bypass any flow control |
| if (pkt->cacheResponding()) { |
| pkt->setExpressSnoop(); |
| } |
| |
| // make sure that the write request (e.g., WriteClean) |
| // will stop at the memory below if this crossbar is its |
| // destination |
| if (pkt->isWrite() && is_destination) { |
| pkt->clearWriteThrough(); |
| } |
| |
| // since it is a normal request, attempt to send the packet |
| success = masterPorts[master_port_id]->sendTimingReq(pkt); |
| } else { |
| // no need to forward, turn this packet around and respond |
| // directly |
| assert(pkt->needsResponse()); |
| |
| respond_directly = true; |
| assert(!expect_snoop_resp); |
| expect_response = false; |
| } |
| } |
| |
| if (snoopFilter && snoop_caches) { |
| // Let the snoop filter know about the success of the send operation |
| snoopFilter->finishRequest(!success, addr, pkt->isSecure()); |
| } |
| |
| // check if we were successful in sending the packet onwards |
| if (!success) { |
| // express snoops should never be forced to retry |
| assert(!is_express_snoop); |
| |
| // restore the header delay |
| pkt->headerDelay = old_header_delay; |
| |
| DPRINTF(CoherentXBar, "%s: src %s packet %s RETRY\n", __func__, |
| src_port->name(), pkt->print()); |
| |
| // update the layer state and schedule an idle event |
| reqLayers[master_port_id]->failedTiming(src_port, |
| clockEdge(Cycles(1))); |
| } else { |
| // express snoops currently bypass the crossbar state entirely |
| if (!is_express_snoop) { |
| // if this particular request will generate a snoop |
| // response |
| if (expect_snoop_resp) { |
| // we should never have an exsiting request outstanding |
| assert(outstandingSnoop.find(pkt->req) == |
| outstandingSnoop.end()); |
| outstandingSnoop.insert(pkt->req); |
| |
| // basic sanity check on the outstanding snoops |
| panic_if(outstandingSnoop.size() > maxOutstandingSnoopCheck, |
| "%s: Outstanding snoop requests exceeded %d\n", |
| name(), maxOutstandingSnoopCheck); |
| } |
| |
| // remember where to route the normal response to |
| if (expect_response || expect_snoop_resp) { |
| assert(routeTo.find(pkt->req) == routeTo.end()); |
| routeTo[pkt->req] = slave_port_id; |
| |
| panic_if(routeTo.size() > maxRoutingTableSizeCheck, |
| "%s: Routing table exceeds %d packets\n", |
| name(), maxRoutingTableSizeCheck); |
| } |
| |
| // update the layer state and schedule an idle event |
| reqLayers[master_port_id]->succeededTiming(packetFinishTime); |
| } |
| |
| // stats updates only consider packets that were successfully sent |
| pktCount[slave_port_id][master_port_id]++; |
| pktSize[slave_port_id][master_port_id] += pkt_size; |
| transDist[pkt_cmd]++; |
| |
| if (is_express_snoop) { |
| snoops++; |
| snoopTraffic += pkt_size; |
| } |
| } |
| |
| if (sink_packet) |
| // queue the packet for deletion |
| pendingDelete.reset(pkt); |
| |
| // normally we respond to the packet we just received if we need to |
| PacketPtr rsp_pkt = pkt; |
| PortID rsp_port_id = slave_port_id; |
| |
| // If this is the destination of the cache clean operation the |
| // crossbar is responsible for responding. This crossbar will |
| // respond when the cache clean is complete. A cache clean |
| // is complete either: |
| // * direcly, if no cache above had a dirty copy of the block |
| // as indicated by the satisfied flag of the packet, or |
| // * when the crossbar has seen both the cache clean request |
| // (CleanSharedReq, CleanInvalidReq) and the corresponding |
| // write (WriteClean) which updates the block in the memory |
| // below. |
| if (success && |
| ((pkt->isClean() && pkt->satisfied()) || |
| pkt->cmd == MemCmd::WriteClean) && |
| is_destination) { |
| PacketPtr deferred_rsp = pkt->isWrite() ? nullptr : pkt; |
| auto cmo_lookup = outstandingCMO.find(pkt->id); |
| if (cmo_lookup != outstandingCMO.end()) { |
| // the cache clean request has already reached this xbar |
| respond_directly = true; |
| if (pkt->isWrite()) { |
| rsp_pkt = cmo_lookup->second; |
| assert(rsp_pkt); |
| |
| // determine the destination |
| const auto route_lookup = routeTo.find(rsp_pkt->req); |
| assert(route_lookup != routeTo.end()); |
| rsp_port_id = route_lookup->second; |
| assert(rsp_port_id != InvalidPortID); |
| assert(rsp_port_id < respLayers.size()); |
| // remove the request from the routing table |
| routeTo.erase(route_lookup); |
| } |
| outstandingCMO.erase(cmo_lookup); |
| } else { |
| respond_directly = false; |
| outstandingCMO.emplace(pkt->id, deferred_rsp); |
| if (!pkt->isWrite()) { |
| assert(routeTo.find(pkt->req) == routeTo.end()); |
| routeTo[pkt->req] = slave_port_id; |
| |
| panic_if(routeTo.size() > maxRoutingTableSizeCheck, |
| "%s: Routing table exceeds %d packets\n", |
| name(), maxRoutingTableSizeCheck); |
| } |
| } |
| } |
| |
| |
| if (respond_directly) { |
| assert(rsp_pkt->needsResponse()); |
| assert(success); |
| |
| rsp_pkt->makeResponse(); |
| |
| if (snoopFilter && !system->bypassCaches()) { |
| // let the snoop filter inspect the response and update its state |
| snoopFilter->updateResponse(rsp_pkt, *slavePorts[rsp_port_id]); |
| } |
| |
| // we send the response after the current packet, even if the |
| // response is not for this packet (e.g. cache clean operation |
| // where both the request and the write packet have to cross |
| // the destination xbar before the response is sent.) |
| Tick response_time = clockEdge() + pkt->headerDelay; |
| rsp_pkt->headerDelay = 0; |
| |
| slavePorts[rsp_port_id]->schedTimingResp(rsp_pkt, response_time); |
| } |
| |
| return success; |
| } |
| |
| bool |
| CoherentXBar::recvTimingResp(PacketPtr pkt, PortID master_port_id) |
| { |
| // determine the source port based on the id |
| MasterPort *src_port = masterPorts[master_port_id]; |
| |
| // determine the destination |
| const auto route_lookup = routeTo.find(pkt->req); |
| assert(route_lookup != routeTo.end()); |
| const PortID slave_port_id = route_lookup->second; |
| assert(slave_port_id != InvalidPortID); |
| assert(slave_port_id < respLayers.size()); |
| |
| // test if the crossbar should be considered occupied for the |
| // current port |
| if (!respLayers[slave_port_id]->tryTiming(src_port)) { |
| DPRINTF(CoherentXBar, "%s: src %s packet %s BUSY\n", __func__, |
| src_port->name(), pkt->print()); |
| return false; |
| } |
| |
| DPRINTF(CoherentXBar, "%s: src %s packet %s\n", __func__, |
| src_port->name(), pkt->print()); |
| |
| // store size and command as they might be modified when |
| // forwarding the packet |
| unsigned int pkt_size = pkt->hasData() ? pkt->getSize() : 0; |
| unsigned int pkt_cmd = pkt->cmdToIndex(); |
| |
| // a response sees the response latency |
| Tick xbar_delay = responseLatency * clockPeriod(); |
| |
| // set the packet header and payload delay |
| calcPacketTiming(pkt, xbar_delay); |
| |
| // determine how long to be crossbar layer is busy |
| Tick packetFinishTime = clockEdge(Cycles(1)) + pkt->payloadDelay; |
| |
| if (snoopFilter && !system->bypassCaches()) { |
| // let the snoop filter inspect the response and update its state |
| snoopFilter->updateResponse(pkt, *slavePorts[slave_port_id]); |
| } |
| |
| // send the packet through the destination slave port and pay for |
| // any outstanding header delay |
| Tick latency = pkt->headerDelay; |
| pkt->headerDelay = 0; |
| slavePorts[slave_port_id]->schedTimingResp(pkt, curTick() + latency); |
| |
| // remove the request from the routing table |
| routeTo.erase(route_lookup); |
| |
| respLayers[slave_port_id]->succeededTiming(packetFinishTime); |
| |
| // stats updates |
| pktCount[slave_port_id][master_port_id]++; |
| pktSize[slave_port_id][master_port_id] += pkt_size; |
| transDist[pkt_cmd]++; |
| |
| return true; |
| } |
| |
| void |
| CoherentXBar::recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id) |
| { |
| DPRINTF(CoherentXBar, "%s: src %s packet %s\n", __func__, |
| masterPorts[master_port_id]->name(), pkt->print()); |
| |
| // update stats here as we know the forwarding will succeed |
| unsigned int pkt_size = pkt->hasData() ? pkt->getSize() : 0; |
| transDist[pkt->cmdToIndex()]++; |
| snoops++; |
| snoopTraffic += pkt_size; |
| |
| // we should only see express snoops from caches |
| assert(pkt->isExpressSnoop()); |
| |
| // set the packet header and payload delay, for now use forward latency |
| // @todo Assess the choice of latency further |
| calcPacketTiming(pkt, forwardLatency * clockPeriod()); |
| |
| // remember if a cache has already committed to responding so we |
| // can see if it changes during the snooping |
| const bool cache_responding = pkt->cacheResponding(); |
| |
| assert(pkt->snoopDelay == 0); |
| |
| if (snoopFilter) { |
| // let the Snoop Filter work its magic and guide probing |
| auto sf_res = snoopFilter->lookupSnoop(pkt); |
| // the time required by a packet to be delivered through |
| // the xbar has to be charged also with to lookup latency |
| // of the snoop filter |
| pkt->headerDelay += sf_res.second * clockPeriod(); |
| DPRINTF(CoherentXBar, "%s: src %s packet %s SF size: %i lat: %i\n", |
| __func__, masterPorts[master_port_id]->name(), pkt->print(), |
| sf_res.first.size(), sf_res.second); |
| |
| // forward to all snoopers |
| forwardTiming(pkt, InvalidPortID, sf_res.first); |
| } else { |
| forwardTiming(pkt, InvalidPortID); |
| } |
| |
| // add the snoop delay to our header delay, and then reset it |
| pkt->headerDelay += pkt->snoopDelay; |
| pkt->snoopDelay = 0; |
| |
| // if we can expect a response, remember how to route it |
| if (!cache_responding && pkt->cacheResponding()) { |
| assert(routeTo.find(pkt->req) == routeTo.end()); |
| routeTo[pkt->req] = master_port_id; |
| } |
| |
| // a snoop request came from a connected slave device (one of |
| // our master ports), and if it is not coming from the slave |
| // device responsible for the address range something is |
| // wrong, hence there is nothing further to do as the packet |
| // would be going back to where it came from |
| assert(findPort(pkt->getAddrRange()) == master_port_id); |
| } |
| |
| bool |
| CoherentXBar::recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id) |
| { |
| // determine the source port based on the id |
| SlavePort* src_port = slavePorts[slave_port_id]; |
| |
| // get the destination |
| const auto route_lookup = routeTo.find(pkt->req); |
| assert(route_lookup != routeTo.end()); |
| const PortID dest_port_id = route_lookup->second; |
| assert(dest_port_id != InvalidPortID); |
| |
| // determine if the response is from a snoop request we |
| // created as the result of a normal request (in which case it |
| // should be in the outstandingSnoop), or if we merely forwarded |
| // someone else's snoop request |
| const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) == |
| outstandingSnoop.end(); |
| |
| // test if the crossbar should be considered occupied for the |
| // current port, note that the check is bypassed if the response |
| // is being passed on as a normal response since this is occupying |
| // the response layer rather than the snoop response layer |
| if (forwardAsSnoop) { |
| assert(dest_port_id < snoopLayers.size()); |
| if (!snoopLayers[dest_port_id]->tryTiming(src_port)) { |
| DPRINTF(CoherentXBar, "%s: src %s packet %s BUSY\n", __func__, |
| src_port->name(), pkt->print()); |
| return false; |
| } |
| } else { |
| // get the master port that mirrors this slave port internally |
| MasterPort* snoop_port = snoopRespPorts[slave_port_id]; |
| assert(dest_port_id < respLayers.size()); |
| if (!respLayers[dest_port_id]->tryTiming(snoop_port)) { |
| DPRINTF(CoherentXBar, "%s: src %s packet %s BUSY\n", __func__, |
| snoop_port->name(), pkt->print()); |
| return false; |
| } |
| } |
| |
| DPRINTF(CoherentXBar, "%s: src %s packet %s\n", __func__, |
| src_port->name(), pkt->print()); |
| |
| // store size and command as they might be modified when |
| // forwarding the packet |
| unsigned int pkt_size = pkt->hasData() ? pkt->getSize() : 0; |
| unsigned int pkt_cmd = pkt->cmdToIndex(); |
| |
| // responses are never express snoops |
| assert(!pkt->isExpressSnoop()); |
| |
| // a snoop response sees the snoop response latency, and if it is |
| // forwarded as a normal response, the response latency |
| Tick xbar_delay = |
| (forwardAsSnoop ? snoopResponseLatency : responseLatency) * |
| clockPeriod(); |
| |
| // set the packet header and payload delay |
| calcPacketTiming(pkt, xbar_delay); |
| |
| // determine how long to be crossbar layer is busy |
| Tick packetFinishTime = clockEdge(Cycles(1)) + pkt->payloadDelay; |
| |
| // forward it either as a snoop response or a normal response |
| if (forwardAsSnoop) { |
| // this is a snoop response to a snoop request we forwarded, |
| // e.g. coming from the L1 and going to the L2, and it should |
| // be forwarded as a snoop response |
| |
| if (snoopFilter) { |
| // update the probe filter so that it can properly track the line |
| snoopFilter->updateSnoopForward(pkt, *slavePorts[slave_port_id], |
| *masterPorts[dest_port_id]); |
| } |
| |
| bool success M5_VAR_USED = |
| masterPorts[dest_port_id]->sendTimingSnoopResp(pkt); |
| pktCount[slave_port_id][dest_port_id]++; |
| pktSize[slave_port_id][dest_port_id] += pkt_size; |
| assert(success); |
| |
| snoopLayers[dest_port_id]->succeededTiming(packetFinishTime); |
| } else { |
| // we got a snoop response on one of our slave ports, |
| // i.e. from a coherent master connected to the crossbar, and |
| // since we created the snoop request as part of recvTiming, |
| // this should now be a normal response again |
| outstandingSnoop.erase(pkt->req); |
| |
| // this is a snoop response from a coherent master, hence it |
| // should never go back to where the snoop response came from, |
| // but instead to where the original request came from |
| assert(slave_port_id != dest_port_id); |
| |
| if (snoopFilter) { |
| // update the probe filter so that it can properly track the line |
| snoopFilter->updateSnoopResponse(pkt, *slavePorts[slave_port_id], |
| *slavePorts[dest_port_id]); |
| } |
| |
| DPRINTF(CoherentXBar, "%s: src %s packet %s FWD RESP\n", __func__, |
| src_port->name(), pkt->print()); |
| |
| // as a normal response, it should go back to a master through |
| // one of our slave ports, we also pay for any outstanding |
| // header latency |
| Tick latency = pkt->headerDelay; |
| pkt->headerDelay = 0; |
| slavePorts[dest_port_id]->schedTimingResp(pkt, curTick() + latency); |
| |
| respLayers[dest_port_id]->succeededTiming(packetFinishTime); |
| } |
| |
| // remove the request from the routing table |
| routeTo.erase(route_lookup); |
| |
| // stats updates |
| transDist[pkt_cmd]++; |
| snoops++; |
| snoopTraffic += pkt_size; |
| |
| return true; |
| } |
| |
| |
| void |
| CoherentXBar::forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id, |
| const std::vector<QueuedSlavePort*>& dests) |
| { |
| DPRINTF(CoherentXBar, "%s for %s\n", __func__, pkt->print()); |
| |
| // snoops should only happen if the system isn't bypassing caches |
| assert(!system->bypassCaches()); |
| |
| unsigned fanout = 0; |
| |
| for (const auto& p: dests) { |
| // we could have gotten this request from a snooping master |
| // (corresponding to our own slave port that is also in |
| // snoopPorts) and should not send it back to where it came |
| // from |
| if (exclude_slave_port_id == InvalidPortID || |
| p->getId() != exclude_slave_port_id) { |
| // cache is not allowed to refuse snoop |
| p->sendTimingSnoopReq(pkt); |
| fanout++; |
| } |
| } |
| |
| // Stats for fanout of this forward operation |
| snoopFanout.sample(fanout); |
| } |
| |
| void |
| CoherentXBar::recvReqRetry(PortID master_port_id) |
| { |
| // responses and snoop responses never block on forwarding them, |
| // so the retry will always be coming from a port to which we |
| // tried to forward a request |
| reqLayers[master_port_id]->recvRetry(); |
| } |
| |
| Tick |
| CoherentXBar::recvAtomicBackdoor(PacketPtr pkt, PortID slave_port_id, |
| MemBackdoorPtr *backdoor) |
| { |
| DPRINTF(CoherentXBar, "%s: src %s packet %s\n", __func__, |
| slavePorts[slave_port_id]->name(), pkt->print()); |
| |
| unsigned int pkt_size = pkt->hasData() ? pkt->getSize() : 0; |
| unsigned int pkt_cmd = pkt->cmdToIndex(); |
| |
| MemCmd snoop_response_cmd = MemCmd::InvalidCmd; |
| Tick snoop_response_latency = 0; |
| |
| // is this the destination point for this packet? (e.g. true if |
| // this xbar is the PoC for a cache maintenance operation to the |
| // PoC) otherwise the destination is any cache that can satisfy |
| // the request |
| const bool is_destination = isDestination(pkt); |
| |
| const bool snoop_caches = !system->bypassCaches() && |
| pkt->cmd != MemCmd::WriteClean; |
| if (snoop_caches) { |
| // forward to all snoopers but the source |
| std::pair<MemCmd, Tick> snoop_result; |
| if (snoopFilter) { |
| // check with the snoop filter where to forward this packet |
| auto sf_res = |
| snoopFilter->lookupRequest(pkt, *slavePorts[slave_port_id]); |
| snoop_response_latency += sf_res.second * clockPeriod(); |
| DPRINTF(CoherentXBar, "%s: src %s packet %s SF size: %i lat: %i\n", |
| __func__, slavePorts[slave_port_id]->name(), pkt->print(), |
| sf_res.first.size(), sf_res.second); |
| |
| // let the snoop filter know about the success of the send |
| // operation, and do it even before sending it onwards to |
| // avoid situations where atomic upward snoops sneak in |
| // between and change the filter state |
| snoopFilter->finishRequest(false, pkt->getAddr(), pkt->isSecure()); |
| |
| if (pkt->isEviction()) { |
| // for block-evicting packets, i.e. writebacks and |
| // clean evictions, there is no need to snoop up, as |
| // all we do is determine if the block is cached or |
| // not, instead just set it here based on the snoop |
| // filter result |
| if (!sf_res.first.empty()) |
| pkt->setBlockCached(); |
| } else { |
| snoop_result = forwardAtomic(pkt, slave_port_id, InvalidPortID, |
| sf_res.first); |
| } |
| } else { |
| snoop_result = forwardAtomic(pkt, slave_port_id); |
| } |
| snoop_response_cmd = snoop_result.first; |
| snoop_response_latency += snoop_result.second; |
| } |
| |
| // set up a sensible default value |
| Tick response_latency = 0; |
| |
| const bool sink_packet = sinkPacket(pkt); |
| |
| // even if we had a snoop response, we must continue and also |
| // perform the actual request at the destination |
| PortID master_port_id = findPort(pkt->getAddrRange()); |
| |
| if (sink_packet) { |
| DPRINTF(CoherentXBar, "%s: Not forwarding %s\n", __func__, |
| pkt->print()); |
| } else { |
| if (forwardPacket(pkt)) { |
| // make sure that the write request (e.g., WriteClean) |
| // will stop at the memory below if this crossbar is its |
| // destination |
| if (pkt->isWrite() && is_destination) { |
| pkt->clearWriteThrough(); |
| } |
| |
| // forward the request to the appropriate destination |
| auto master = masterPorts[master_port_id]; |
| response_latency = backdoor ? |
| master->sendAtomicBackdoor(pkt, *backdoor) : |
| master->sendAtomic(pkt); |
| } else { |
| // if it does not need a response we sink the packet above |
| assert(pkt->needsResponse()); |
| |
| pkt->makeResponse(); |
| } |
| } |
| |
| // stats updates for the request |
| pktCount[slave_port_id][master_port_id]++; |
| pktSize[slave_port_id][master_port_id] += pkt_size; |
| transDist[pkt_cmd]++; |
| |
| |
| // if lower levels have replied, tell the snoop filter |
| if (!system->bypassCaches() && snoopFilter && pkt->isResponse()) { |
| snoopFilter->updateResponse(pkt, *slavePorts[slave_port_id]); |
| } |
| |
| // if we got a response from a snooper, restore it here |
| if (snoop_response_cmd != MemCmd::InvalidCmd) { |
| // no one else should have responded |
| assert(!pkt->isResponse()); |
| pkt->cmd = snoop_response_cmd; |
| response_latency = snoop_response_latency; |
| } |
| |
| // If this is the destination of the cache clean operation the |
| // crossbar is responsible for responding. This crossbar will |
| // respond when the cache clean is complete. An atomic cache clean |
| // is complete when the crossbars receives the cache clean |
| // request (CleanSharedReq, CleanInvalidReq), as either: |
| // * no cache above had a dirty copy of the block as indicated by |
| // the satisfied flag of the packet, or |
| // * the crossbar has already seen the corresponding write |
| // (WriteClean) which updates the block in the memory below. |
| if (pkt->isClean() && isDestination(pkt) && pkt->satisfied()) { |
| auto it = outstandingCMO.find(pkt->id); |
| assert(it != outstandingCMO.end()); |
| // we are responding right away |
| outstandingCMO.erase(it); |
| } else if (pkt->cmd == MemCmd::WriteClean && isDestination(pkt)) { |
| // if this is the destination of the operation, the xbar |
| // sends the responce to the cache clean operation only |
| // after having encountered the cache clean request |
| auto M5_VAR_USED ret = outstandingCMO.emplace(pkt->id, nullptr); |
| // in atomic mode we know that the WriteClean packet should |
| // precede the clean request |
| assert(ret.second); |
| } |
| |
| // add the response data |
| if (pkt->isResponse()) { |
| pkt_size = pkt->hasData() ? pkt->getSize() : 0; |
| pkt_cmd = pkt->cmdToIndex(); |
| |
| // stats updates |
| pktCount[slave_port_id][master_port_id]++; |
| pktSize[slave_port_id][master_port_id] += pkt_size; |
| transDist[pkt_cmd]++; |
| } |
| |
| // @todo: Not setting header time |
| pkt->payloadDelay = response_latency; |
| return response_latency; |
| } |
| |
| Tick |
| CoherentXBar::recvAtomicSnoop(PacketPtr pkt, PortID master_port_id) |
| { |
| DPRINTF(CoherentXBar, "%s: src %s packet %s\n", __func__, |
| masterPorts[master_port_id]->name(), pkt->print()); |
| |
| // add the request snoop data |
| unsigned int pkt_size = pkt->hasData() ? pkt->getSize() : 0; |
| snoops++; |
| snoopTraffic += pkt_size; |
| |
| // forward to all snoopers |
| std::pair<MemCmd, Tick> snoop_result; |
| Tick snoop_response_latency = 0; |
| if (snoopFilter) { |
| auto sf_res = snoopFilter->lookupSnoop(pkt); |
| snoop_response_latency += sf_res.second * clockPeriod(); |
| DPRINTF(CoherentXBar, "%s: src %s packet %s SF size: %i lat: %i\n", |
| __func__, masterPorts[master_port_id]->name(), pkt->print(), |
| sf_res.first.size(), sf_res.second); |
| snoop_result = forwardAtomic(pkt, InvalidPortID, master_port_id, |
| sf_res.first); |
| } else { |
| snoop_result = forwardAtomic(pkt, InvalidPortID); |
| } |
| MemCmd snoop_response_cmd = snoop_result.first; |
| snoop_response_latency += snoop_result.second; |
| |
| if (snoop_response_cmd != MemCmd::InvalidCmd) |
| pkt->cmd = snoop_response_cmd; |
| |
| // add the response snoop data |
| if (pkt->isResponse()) { |
| snoops++; |
| } |
| |
| // @todo: Not setting header time |
| pkt->payloadDelay = snoop_response_latency; |
| return snoop_response_latency; |
| } |
| |
| std::pair<MemCmd, Tick> |
| CoherentXBar::forwardAtomic(PacketPtr pkt, PortID exclude_slave_port_id, |
| PortID source_master_port_id, |
| const std::vector<QueuedSlavePort*>& dests) |
| { |
| // the packet may be changed on snoops, record the original |
| // command to enable us to restore it between snoops so that |
| // additional snoops can take place properly |
| MemCmd orig_cmd = pkt->cmd; |
| MemCmd snoop_response_cmd = MemCmd::InvalidCmd; |
| Tick snoop_response_latency = 0; |
| |
| // snoops should only happen if the system isn't bypassing caches |
| assert(!system->bypassCaches()); |
| |
| unsigned fanout = 0; |
| |
| for (const auto& p: dests) { |
| // we could have gotten this request from a snooping master |
| // (corresponding to our own slave port that is also in |
| // snoopPorts) and should not send it back to where it came |
| // from |
| if (exclude_slave_port_id != InvalidPortID && |
| p->getId() == exclude_slave_port_id) |
| continue; |
| |
| Tick latency = p->sendAtomicSnoop(pkt); |
| fanout++; |
| |
| // in contrast to a functional access, we have to keep on |
| // going as all snoopers must be updated even if we get a |
| // response |
| if (!pkt->isResponse()) |
| continue; |
| |
| // response from snoop agent |
| assert(pkt->cmd != orig_cmd); |
| assert(pkt->cacheResponding()); |
| // should only happen once |
| assert(snoop_response_cmd == MemCmd::InvalidCmd); |
| // save response state |
| snoop_response_cmd = pkt->cmd; |
| snoop_response_latency = latency; |
| |
| if (snoopFilter) { |
| // Handle responses by the snoopers and differentiate between |
| // responses to requests from above and snoops from below |
| if (source_master_port_id != InvalidPortID) { |
| // Getting a response for a snoop from below |
| assert(exclude_slave_port_id == InvalidPortID); |
| snoopFilter->updateSnoopForward(pkt, *p, |
| *masterPorts[source_master_port_id]); |
| } else { |
| // Getting a response for a request from above |
| assert(source_master_port_id == InvalidPortID); |
| snoopFilter->updateSnoopResponse(pkt, *p, |
| *slavePorts[exclude_slave_port_id]); |
| } |
| } |
| // restore original packet state for remaining snoopers |
| pkt->cmd = orig_cmd; |
| } |
| |
| // Stats for fanout |
| snoopFanout.sample(fanout); |
| |
| // the packet is restored as part of the loop and any potential |
| // snoop response is part of the returned pair |
| return std::make_pair(snoop_response_cmd, snoop_response_latency); |
| } |
| |
| void |
| CoherentXBar::recvFunctional(PacketPtr pkt, PortID slave_port_id) |
| { |
| if (!pkt->isPrint()) { |
| // don't do DPRINTFs on PrintReq as it clutters up the output |
| DPRINTF(CoherentXBar, "%s: src %s packet %s\n", __func__, |
| slavePorts[slave_port_id]->name(), pkt->print()); |
| } |
| |
| if (!system->bypassCaches()) { |
| // forward to all snoopers but the source |
| forwardFunctional(pkt, slave_port_id); |
| } |
| |
| // there is no need to continue if the snooping has found what we |
| // were looking for and the packet is already a response |
| if (!pkt->isResponse()) { |
| // since our slave ports are queued ports we need to check them as well |
| for (const auto& p : slavePorts) { |
| // if we find a response that has the data, then the |
| // downstream caches/memories may be out of date, so simply stop |
| // here |
| if (p->trySatisfyFunctional(pkt)) { |
| if (pkt->needsResponse()) |
| pkt->makeResponse(); |
| return; |
| } |
| } |
| |
| PortID dest_id = findPort(pkt->getAddrRange()); |
| |
| masterPorts[dest_id]->sendFunctional(pkt); |
| } |
| } |
| |
| void |
| CoherentXBar::recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id) |
| { |
| if (!pkt->isPrint()) { |
| // don't do DPRINTFs on PrintReq as it clutters up the output |
| DPRINTF(CoherentXBar, "%s: src %s packet %s\n", __func__, |
| masterPorts[master_port_id]->name(), pkt->print()); |
| } |
| |
| for (const auto& p : slavePorts) { |
| if (p->trySatisfyFunctional(pkt)) { |
| if (pkt->needsResponse()) |
| pkt->makeResponse(); |
| return; |
| } |
| } |
| |
| // forward to all snoopers |
| forwardFunctional(pkt, InvalidPortID); |
| } |
| |
| void |
| CoherentXBar::forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id) |
| { |
| // snoops should only happen if the system isn't bypassing caches |
| assert(!system->bypassCaches()); |
| |
| for (const auto& p: snoopPorts) { |
| // we could have gotten this request from a snooping master |
| // (corresponding to our own slave port that is also in |
| // snoopPorts) and should not send it back to where it came |
| // from |
| if (exclude_slave_port_id == InvalidPortID || |
| p->getId() != exclude_slave_port_id) |
| p->sendFunctionalSnoop(pkt); |
| |
| // if we get a response we are done |
| if (pkt->isResponse()) { |
| break; |
| } |
| } |
| } |
| |
| bool |
| CoherentXBar::sinkPacket(const PacketPtr pkt) const |
| { |
| // we can sink the packet if: |
| // 1) the crossbar is the point of coherency, and a cache is |
| // responding after being snooped |
| // 2) the crossbar is the point of coherency, and the packet is a |
| // coherency packet (not a read or a write) that does not |
| // require a response |
| // 3) this is a clean evict or clean writeback, but the packet is |
| // found in a cache above this crossbar |
| // 4) a cache is responding after being snooped, and the packet |
| // either does not need the block to be writable, or the cache |
| // that has promised to respond (setting the cache responding |
| // flag) is providing writable and thus had a Modified block, |
| // and no further action is needed |
| return (pointOfCoherency && pkt->cacheResponding()) || |
| (pointOfCoherency && !(pkt->isRead() || pkt->isWrite()) && |
| !pkt->needsResponse()) || |
| (pkt->isCleanEviction() && pkt->isBlockCached()) || |
| (pkt->cacheResponding() && |
| (!pkt->needsWritable() || pkt->responderHadWritable())); |
| } |
| |
| bool |
| CoherentXBar::forwardPacket(const PacketPtr pkt) |
| { |
| // we are forwarding the packet if: |
| // 1) this is a cache clean request to the PoU/PoC and this |
| // crossbar is above the PoU/PoC |
| // 2) this is a read or a write |
| // 3) this crossbar is above the point of coherency |
| if (pkt->isClean()) { |
| return !isDestination(pkt); |
| } |
| return pkt->isRead() || pkt->isWrite() || !pointOfCoherency; |
| } |
| |
| |
| void |
| CoherentXBar::regStats() |
| { |
| // register the stats of the base class and our layers |
| BaseXBar::regStats(); |
| for (auto l: reqLayers) |
| l->regStats(); |
| for (auto l: respLayers) |
| l->regStats(); |
| for (auto l: snoopLayers) |
| l->regStats(); |
| |
| snoops |
| .name(name() + ".snoops") |
| .desc("Total snoops (count)") |
| ; |
| |
| snoopTraffic |
| .name(name() + ".snoopTraffic") |
| .desc("Total snoop traffic (bytes)") |
| ; |
| |
| snoopFanout |
| .init(0, snoopPorts.size(), 1) |
| .name(name() + ".snoop_fanout") |
| .desc("Request fanout histogram") |
| ; |
| } |
| |
| CoherentXBar * |
| CoherentXBarParams::create() |
| { |
| return new CoherentXBar(this); |
| } |
