/* * Copyright (c) 2010-2013 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) 2013 Amin Farmahini-Farahani * 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: Andreas Hansson * Ani Udipi * Neha Agarwal */ #include "base/trace.hh" #include "base/bitfield.hh" #include "debug/Drain.hh" #include "debug/DRAM.hh" #include "mem/simple_dram.hh" #include "sim/system.hh" using namespace std; SimpleDRAM::SimpleDRAM(const SimpleDRAMParams* p) : AbstractMemory(p), port(name() + ".port", *this), retryRdReq(false), retryWrReq(false), rowHitFlag(false), stopReads(false), writeEvent(this), respondEvent(this), refreshEvent(this), nextReqEvent(this), drainManager(NULL), deviceBusWidth(p->device_bus_width), burstLength(p->burst_length), deviceRowBufferSize(p->device_rowbuffer_size), devicesPerRank(p->devices_per_rank), burstSize((devicesPerRank * burstLength * deviceBusWidth) / 8), rowBufferSize(devicesPerRank * deviceRowBufferSize), ranksPerChannel(p->ranks_per_channel), banksPerRank(p->banks_per_rank), channels(p->channels), rowsPerBank(0), readBufferSize(p->read_buffer_size), writeBufferSize(p->write_buffer_size), writeHighThresholdPerc(p->write_high_thresh_perc), writeLowThresholdPerc(p->write_low_thresh_perc), tWTR(p->tWTR), tBURST(p->tBURST), tRCD(p->tRCD), tCL(p->tCL), tRP(p->tRP), tRAS(p->tRAS), tRFC(p->tRFC), tREFI(p->tREFI), tRRD(p->tRRD), tXAW(p->tXAW), activationLimit(p->activation_limit), memSchedPolicy(p->mem_sched_policy), addrMapping(p->addr_mapping), pageMgmt(p->page_policy), frontendLatency(p->static_frontend_latency), backendLatency(p->static_backend_latency), busBusyUntil(0), writeStartTime(0), prevArrival(0), numReqs(0), numWritesThisTime(0), newTime(0) { // create the bank states based on the dimensions of the ranks and // banks banks.resize(ranksPerChannel); actTicks.resize(ranksPerChannel); for (size_t c = 0; c < ranksPerChannel; ++c) { banks[c].resize(banksPerRank); actTicks[c].resize(activationLimit, 0); } // round the write thresholds percent to a whole number of entries // in the buffer. writeHighThreshold = writeBufferSize * writeHighThresholdPerc / 100.0; writeLowThreshold = writeBufferSize * writeLowThresholdPerc / 100.0; } void SimpleDRAM::init() { if (!port.isConnected()) { fatal("SimpleDRAM %s is unconnected!\n", name()); } else { port.sendRangeChange(); } // we could deal with plenty options here, but for now do a quick // sanity check DPRINTF(DRAM, "Burst size %d bytes\n", burstSize); // determine the rows per bank by looking at the total capacity uint64_t capacity = ULL(1) << ceilLog2(AbstractMemory::size()); DPRINTF(DRAM, "Memory capacity %lld (%lld) bytes\n", capacity, AbstractMemory::size()); columnsPerRowBuffer = rowBufferSize / burstSize; DPRINTF(DRAM, "Row buffer size %d bytes with %d columns per row buffer\n", rowBufferSize, columnsPerRowBuffer); rowsPerBank = capacity / (rowBufferSize * banksPerRank * ranksPerChannel); if (range.interleaved()) { if (channels != range.stripes()) panic("%s has %d interleaved address stripes but %d channel(s)\n", name(), range.stripes(), channels); if (addrMapping == Enums::RaBaChCo) { if (rowBufferSize != range.granularity()) { panic("Interleaving of %s doesn't match RaBaChCo address map\n", name()); } } else if (addrMapping == Enums::RaBaCoCh) { if (burstSize != range.granularity()) { panic("Interleaving of %s doesn't match RaBaCoCh address map\n", name()); } } else if (addrMapping == Enums::CoRaBaCh) { if (burstSize != range.granularity()) panic("Interleaving of %s doesn't match CoRaBaCh address map\n", name()); } } } void SimpleDRAM::startup() { // print the configuration of the controller printParams(); // kick off the refresh schedule(refreshEvent, curTick() + tREFI); } Tick SimpleDRAM::recvAtomic(PacketPtr pkt) { DPRINTF(DRAM, "recvAtomic: %s 0x%x\n", pkt->cmdString(), pkt->getAddr()); // do the actual memory access and turn the packet into a response access(pkt); Tick latency = 0; if (!pkt->memInhibitAsserted() && pkt->hasData()) { // this value is not supposed to be accurate, just enough to // keep things going, mimic a closed page latency = tRP + tRCD + tCL; } return latency; } bool SimpleDRAM::readQueueFull(unsigned int neededEntries) const { DPRINTF(DRAM, "Read queue limit %d, current size %d, entries needed %d\n", readBufferSize, readQueue.size() + respQueue.size(), neededEntries); return (readQueue.size() + respQueue.size() + neededEntries) > readBufferSize; } bool SimpleDRAM::writeQueueFull(unsigned int neededEntries) const { DPRINTF(DRAM, "Write queue limit %d, current size %d, entries needed %d\n", writeBufferSize, writeQueue.size(), neededEntries); return (writeQueue.size() + neededEntries) > writeBufferSize; } SimpleDRAM::DRAMPacket* SimpleDRAM::decodeAddr(PacketPtr pkt, Addr dramPktAddr, unsigned size, bool isRead) { // decode the address based on the address mapping scheme, with // Ra, Co, Ba and Ch denoting rank, column, bank and channel, // respectively uint8_t rank; uint8_t bank; uint16_t row; // truncate the address to the access granularity Addr addr = dramPktAddr / burstSize; // we have removed the lowest order address bits that denote the // position within the column if (addrMapping == Enums::RaBaChCo) { // the lowest order bits denote the column to ensure that // sequential cache lines occupy the same row addr = addr / columnsPerRowBuffer; // take out the channel part of the address addr = addr / channels; // after the channel bits, get the bank bits to interleave // over the banks bank = addr % banksPerRank; addr = addr / banksPerRank; // after the bank, we get the rank bits which thus interleaves // over the ranks rank = addr % ranksPerChannel; addr = addr / ranksPerChannel; // lastly, get the row bits row = addr % rowsPerBank; addr = addr / rowsPerBank; } else if (addrMapping == Enums::RaBaCoCh) { // take out the channel part of the address addr = addr / channels; // next, the column addr = addr / columnsPerRowBuffer; // after the column bits, we get the bank bits to interleave // over the banks bank = addr % banksPerRank; addr = addr / banksPerRank; // after the bank, we get the rank bits which thus interleaves // over the ranks rank = addr % ranksPerChannel; addr = addr / ranksPerChannel; // lastly, get the row bits row = addr % rowsPerBank; addr = addr / rowsPerBank; } else if (addrMapping == Enums::CoRaBaCh) { // optimise for closed page mode and utilise maximum // parallelism of the DRAM (at the cost of power) // take out the channel part of the address, not that this has // to match with how accesses are interleaved between the // controllers in the address mapping addr = addr / channels; // start with the bank bits, as this provides the maximum // opportunity for parallelism between requests bank = addr % banksPerRank; addr = addr / banksPerRank; // next get the rank bits rank = addr % ranksPerChannel; addr = addr / ranksPerChannel; // next the column bits which we do not need to keep track of // and simply skip past addr = addr / columnsPerRowBuffer; // lastly, get the row bits row = addr % rowsPerBank; addr = addr / rowsPerBank; } else panic("Unknown address mapping policy chosen!"); assert(rank < ranksPerChannel); assert(bank < banksPerRank); assert(row < rowsPerBank); DPRINTF(DRAM, "Address: %lld Rank %d Bank %d Row %d\n", dramPktAddr, rank, bank, row); // create the corresponding DRAM packet with the entry time and // ready time set to the current tick, the latter will be updated // later uint16_t bank_id = banksPerRank * rank + bank; return new DRAMPacket(pkt, isRead, rank, bank, row, bank_id, dramPktAddr, size, banks[rank][bank]); } void SimpleDRAM::addToReadQueue(PacketPtr pkt, unsigned int pktCount) { // only add to the read queue here. whenever the request is // eventually done, set the readyTime, and call schedule() assert(!pkt->isWrite()); assert(pktCount != 0); // if the request size is larger than burst size, the pkt is split into // multiple DRAM packets // Note if the pkt starting address is not aligened to burst size, the // address of first DRAM packet is kept unaliged. Subsequent DRAM packets // are aligned to burst size boundaries. This is to ensure we accurately // check read packets against packets in write queue. Addr addr = pkt->getAddr(); unsigned pktsServicedByWrQ = 0; BurstHelper* burst_helper = NULL; for (int cnt = 0; cnt < pktCount; ++cnt) { unsigned size = std::min((addr | (burstSize - 1)) + 1, pkt->getAddr() + pkt->getSize()) - addr; readPktSize[ceilLog2(size)]++; readBursts++; // First check write buffer to see if the data is already at // the controller bool foundInWrQ = false; for (auto i = writeQueue.begin(); i != writeQueue.end(); ++i) { // check if the read is subsumed in the write entry we are // looking at if ((*i)->addr <= addr && (addr + size) <= ((*i)->addr + (*i)->size)) { foundInWrQ = true; servicedByWrQ++; pktsServicedByWrQ++; DPRINTF(DRAM, "Read to addr %lld with size %d serviced by " "write queue\n", addr, size); bytesRead += burstSize; bytesConsumedRd += size; break; } } // If not found in the write q, make a DRAM packet and // push it onto the read queue if (!foundInWrQ) { // Make the burst helper for split packets if (pktCount > 1 && burst_helper == NULL) { DPRINTF(DRAM, "Read to addr %lld translates to %d " "dram requests\n", pkt->getAddr(), pktCount); burst_helper = new BurstHelper(pktCount); } DRAMPacket* dram_pkt = decodeAddr(pkt, addr, size, true); dram_pkt->burstHelper = burst_helper; assert(!readQueueFull(1)); rdQLenPdf[readQueue.size() + respQueue.size()]++; DPRINTF(DRAM, "Adding to read queue\n"); readQueue.push_back(dram_pkt); // Update stats assert(dram_pkt->bankId < ranksPerChannel * banksPerRank); perBankRdReqs[dram_pkt->bankId]++; avgRdQLen = readQueue.size() + respQueue.size(); } // Starting address of next dram pkt (aligend to burstSize boundary) addr = (addr | (burstSize - 1)) + 1; } // If all packets are serviced by write queue, we send the repsonse back if (pktsServicedByWrQ == pktCount) { accessAndRespond(pkt, frontendLatency); return; } // Update how many split packets are serviced by write queue if (burst_helper != NULL) burst_helper->burstsServiced = pktsServicedByWrQ; // If we are not already scheduled to get the read request out of // the queue, do so now if (!nextReqEvent.scheduled() && !stopReads) { DPRINTF(DRAM, "Request scheduled immediately\n"); schedule(nextReqEvent, curTick()); } } void SimpleDRAM::processWriteEvent() { assert(!writeQueue.empty()); DPRINTF(DRAM, "Beginning DRAM Write\n"); Tick temp1 M5_VAR_USED = std::max(curTick(), busBusyUntil); Tick temp2 M5_VAR_USED = std::max(curTick(), maxBankFreeAt()); chooseNextWrite(); DRAMPacket* dram_pkt = writeQueue.front(); // sanity check assert(dram_pkt->size <= burstSize); doDRAMAccess(dram_pkt); writeQueue.pop_front(); delete dram_pkt; numWritesThisTime++; DPRINTF(DRAM, "Completed %d writes, bus busy for %lld ticks,"\ "banks busy for %lld ticks\n", numWritesThisTime, busBusyUntil - temp1, maxBankFreeAt() - temp2); // Update stats avgWrQLen = writeQueue.size(); if (numWritesThisTime >= writeHighThreshold) { DPRINTF(DRAM, "Hit write threshold %d\n", writeHighThreshold); } // If number of writes in the queue fall below the low thresholds and // read queue is not empty then schedule a request event else continue // with writes. The retry above could already have caused it to be // scheduled, so first check if (((writeQueue.size() <= writeLowThreshold) && !readQueue.empty()) || writeQueue.empty()) { numWritesThisTime = 0; // turn the bus back around for reads again busBusyUntil += tWTR; stopReads = false; if (!nextReqEvent.scheduled()) schedule(nextReqEvent, busBusyUntil); } else { assert(!writeEvent.scheduled()); DPRINTF(DRAM, "Next write scheduled at %lld\n", newTime); schedule(writeEvent, newTime); } if (retryWrReq) { retryWrReq = false; port.sendRetry(); } // if there is nothing left in any queue, signal a drain if (writeQueue.empty() && readQueue.empty() && respQueue.empty () && drainManager) { drainManager->signalDrainDone(); drainManager = NULL; } } void SimpleDRAM::triggerWrites() { DPRINTF(DRAM, "Writes triggered at %lld\n", curTick()); // Flag variable to stop any more read scheduling stopReads = true; writeStartTime = std::max(busBusyUntil, curTick()) + tWTR; DPRINTF(DRAM, "Writes scheduled at %lld\n", writeStartTime); assert(writeStartTime >= curTick()); assert(!writeEvent.scheduled()); schedule(writeEvent, writeStartTime); } void SimpleDRAM::addToWriteQueue(PacketPtr pkt, unsigned int pktCount) { // only add to the write queue here. whenever the request is // eventually done, set the readyTime, and call schedule() assert(pkt->isWrite()); // if the request size is larger than burst size, the pkt is split into // multiple DRAM packets Addr addr = pkt->getAddr(); for (int cnt = 0; cnt < pktCount; ++cnt) { unsigned size = std::min((addr | (burstSize - 1)) + 1, pkt->getAddr() + pkt->getSize()) - addr; writePktSize[ceilLog2(size)]++; writeBursts++; // see if we can merge with an existing item in the write // queue and keep track of whether we have merged or not so we // can stop at that point and also avoid enqueueing a new // request bool merged = false; auto w = writeQueue.begin(); while(!merged && w != writeQueue.end()) { // either of the two could be first, if they are the same // it does not matter which way we go if ((*w)->addr >= addr) { // the existing one starts after the new one, figure // out where the new one ends with respect to the // existing one if ((addr + size) >= ((*w)->addr + (*w)->size)) { // check if the existing one is completely // subsumed in the new one DPRINTF(DRAM, "Merging write covering existing burst\n"); merged = true; // update both the address and the size (*w)->addr = addr; (*w)->size = size; } else if ((addr + size) >= (*w)->addr && ((*w)->addr + (*w)->size - addr) <= burstSize) { // the new one is just before or partially // overlapping with the existing one, and together // they fit within a burst DPRINTF(DRAM, "Merging write before existing burst\n"); merged = true; // the existing queue item needs to be adjusted with // respect to both address and size (*w)->addr = addr; (*w)->size = (*w)->addr + (*w)->size - addr; } } else { // the new one starts after the current one, figure // out where the existing one ends with respect to the // new one if (((*w)->addr + (*w)->size) >= (addr + size)) { // check if the new one is completely subsumed in the // existing one DPRINTF(DRAM, "Merging write into existing burst\n"); merged = true; // no adjustments necessary } else if (((*w)->addr + (*w)->size) >= addr && (addr + size - (*w)->addr) <= burstSize) { // the existing one is just before or partially // overlapping with the new one, and together // they fit within a burst DPRINTF(DRAM, "Merging write after existing burst\n"); merged = true; // the address is right, and only the size has // to be adjusted (*w)->size = addr + size - (*w)->addr; } } ++w; } // if the item was not merged we need to create a new write // and enqueue it if (!merged) { DRAMPacket* dram_pkt = decodeAddr(pkt, addr, size, false); assert(writeQueue.size() < writeBufferSize); wrQLenPdf[writeQueue.size()]++; DPRINTF(DRAM, "Adding to write queue\n"); writeQueue.push_back(dram_pkt); // Update stats assert(dram_pkt->bankId < ranksPerChannel * banksPerRank); perBankWrReqs[dram_pkt->bankId]++; avgWrQLen = writeQueue.size(); } bytesConsumedWr += size; bytesWritten += burstSize; // Starting address of next dram pkt (aligend to burstSize boundary) addr = (addr | (burstSize - 1)) + 1; } // we do not wait for the writes to be send to the actual memory, // but instead take responsibility for the consistency here and // snoop the write queue for any upcoming reads // @todo, if a pkt size is larger than burst size, we might need a // different front end latency accessAndRespond(pkt, frontendLatency); // If your write buffer is starting to fill up, drain it! if (writeQueue.size() >= writeHighThreshold && !stopReads){ triggerWrites(); } } void SimpleDRAM::printParams() const { // Sanity check print of important parameters DPRINTF(DRAM, "Memory controller %s physical organization\n" \ "Number of devices per rank %d\n" \ "Device bus width (in bits) %d\n" \ "DRAM data bus burst %d\n" \ "Row buffer size %d\n" \ "Columns per row buffer %d\n" \ "Rows per bank %d\n" \ "Banks per rank %d\n" \ "Ranks per channel %d\n" \ "Total mem capacity %u\n", name(), devicesPerRank, deviceBusWidth, burstSize, rowBufferSize, columnsPerRowBuffer, rowsPerBank, banksPerRank, ranksPerChannel, rowBufferSize * rowsPerBank * banksPerRank * ranksPerChannel); string scheduler = memSchedPolicy == Enums::fcfs ? "FCFS" : "FR-FCFS"; string address_mapping = addrMapping == Enums::RaBaChCo ? "RaBaChCo" : (addrMapping == Enums::RaBaCoCh ? "RaBaCoCh" : "CoRaBaCh"); string page_policy = pageMgmt == Enums::open ? "OPEN" : (pageMgmt == Enums::open_adaptive ? "OPEN (adaptive)" : "CLOSE"); DPRINTF(DRAM, "Memory controller %s characteristics\n" \ "Read buffer size %d\n" \ "Write buffer size %d\n" \ "Write buffer thresh %d\n" \ "Scheduler %s\n" \ "Address mapping %s\n" \ "Page policy %s\n", name(), readBufferSize, writeBufferSize, writeHighThreshold, scheduler, address_mapping, page_policy); DPRINTF(DRAM, "Memory controller %s timing specs\n" \ "tRCD %d ticks\n" \ "tCL %d ticks\n" \ "tRP %d ticks\n" \ "tBURST %d ticks\n" \ "tRFC %d ticks\n" \ "tREFI %d ticks\n" \ "tWTR %d ticks\n" \ "tXAW (%d) %d ticks\n", name(), tRCD, tCL, tRP, tBURST, tRFC, tREFI, tWTR, activationLimit, tXAW); } void SimpleDRAM::printQs() const { DPRINTF(DRAM, "===READ QUEUE===\n\n"); for (auto i = readQueue.begin() ; i != readQueue.end() ; ++i) { DPRINTF(DRAM, "Read %lu\n", (*i)->addr); } DPRINTF(DRAM, "\n===RESP QUEUE===\n\n"); for (auto i = respQueue.begin() ; i != respQueue.end() ; ++i) { DPRINTF(DRAM, "Response %lu\n", (*i)->addr); } DPRINTF(DRAM, "\n===WRITE QUEUE===\n\n"); for (auto i = writeQueue.begin() ; i != writeQueue.end() ; ++i) { DPRINTF(DRAM, "Write %lu\n", (*i)->addr); } } bool SimpleDRAM::recvTimingReq(PacketPtr pkt) { /// @todo temporary hack to deal with memory corruption issues until /// 4-phase transactions are complete for (int x = 0; x < pendingDelete.size(); x++) delete pendingDelete[x]; pendingDelete.clear(); // This is where we enter from the outside world DPRINTF(DRAM, "recvTimingReq: request %s addr %lld size %d\n", pkt->cmdString(), pkt->getAddr(), pkt->getSize()); // simply drop inhibited packets for now if (pkt->memInhibitAsserted()) { DPRINTF(DRAM,"Inhibited packet -- Dropping it now\n"); pendingDelete.push_back(pkt); return true; } // Every million accesses, print the state of the queues if (numReqs % 1000000 == 0) printQs(); // Calc avg gap between requests if (prevArrival != 0) { totGap += curTick() - prevArrival; } prevArrival = curTick(); // Find out how many dram packets a pkt translates to // If the burst size is equal or larger than the pkt size, then a pkt // translates to only one dram packet. Otherwise, a pkt translates to // multiple dram packets unsigned size = pkt->getSize(); unsigned offset = pkt->getAddr() & (burstSize - 1); unsigned int dram_pkt_count = divCeil(offset + size, burstSize); // check local buffers and do not accept if full if (pkt->isRead()) { assert(size != 0); if (readQueueFull(dram_pkt_count)) { DPRINTF(DRAM, "Read queue full, not accepting\n"); // remember that we have to retry this port retryRdReq = true; numRdRetry++; return false; } else { addToReadQueue(pkt, dram_pkt_count); readReqs++; numReqs++; } } else if (pkt->isWrite()) { assert(size != 0); if (writeQueueFull(dram_pkt_count)) { DPRINTF(DRAM, "Write queue full, not accepting\n"); // remember that we have to retry this port retryWrReq = true; numWrRetry++; return false; } else { addToWriteQueue(pkt, dram_pkt_count); writeReqs++; numReqs++; } } else { DPRINTF(DRAM,"Neither read nor write, ignore timing\n"); neitherReadNorWrite++; accessAndRespond(pkt, 1); } retryRdReq = false; retryWrReq = false; return true; } void SimpleDRAM::processRespondEvent() { DPRINTF(DRAM, "processRespondEvent(): Some req has reached its readyTime\n"); DRAMPacket* dram_pkt = respQueue.front(); // Actually responds to the requestor bytesConsumedRd += dram_pkt->size; bytesRead += burstSize; if (dram_pkt->burstHelper) { // it is a split packet dram_pkt->burstHelper->burstsServiced++; if (dram_pkt->burstHelper->burstsServiced == dram_pkt->burstHelper->burstCount) { // we have now serviced all children packets of a system packet // so we can now respond to the requester // @todo we probably want to have a different front end and back // end latency for split packets accessAndRespond(dram_pkt->pkt, frontendLatency + backendLatency); delete dram_pkt->burstHelper; dram_pkt->burstHelper = NULL; } } else { // it is not a split packet accessAndRespond(dram_pkt->pkt, frontendLatency + backendLatency); } delete respQueue.front(); respQueue.pop_front(); // Update stats avgRdQLen = readQueue.size() + respQueue.size(); if (!respQueue.empty()) { assert(respQueue.front()->readyTime >= curTick()); assert(!respondEvent.scheduled()); schedule(respondEvent, respQueue.front()->readyTime); } else { // if there is nothing left in any queue, signal a drain if (writeQueue.empty() && readQueue.empty() && drainManager) { drainManager->signalDrainDone(); drainManager = NULL; } } // We have made a location in the queue available at this point, // so if there is a read that was forced to wait, retry now if (retryRdReq) { retryRdReq = false; port.sendRetry(); } } void SimpleDRAM::chooseNextWrite() { // This method does the arbitration between write requests. The // chosen packet is simply moved to the head of the write // queue. The other methods know that this is the place to // look. For example, with FCFS, this method does nothing assert(!writeQueue.empty()); if (writeQueue.size() == 1) { DPRINTF(DRAM, "Single write request, nothing to do\n"); return; } if (memSchedPolicy == Enums::fcfs) { // Do nothing, since the correct request is already head } else if (memSchedPolicy == Enums::frfcfs) { // Only determine bank availability when needed uint64_t earliest_banks = 0; auto i = writeQueue.begin(); bool foundRowHit = false; while (!foundRowHit && i != writeQueue.end()) { DRAMPacket* dram_pkt = *i; const Bank& bank = dram_pkt->bankRef; if (bank.openRow == dram_pkt->row) { DPRINTF(DRAM, "Write row buffer hit\n"); writeQueue.erase(i); writeQueue.push_front(dram_pkt); foundRowHit = true; } else { // No row hit, go for first ready if (earliest_banks == 0) earliest_banks = minBankFreeAt(writeQueue); // Bank is ready or is one of the first available bank if (bank.freeAt <= curTick() || bits(earliest_banks, dram_pkt->bankId, dram_pkt->bankId)) { writeQueue.erase(i); writeQueue.push_front(dram_pkt); break; } } ++i; } } else panic("No scheduling policy chosen\n"); DPRINTF(DRAM, "Selected next write request\n"); } bool SimpleDRAM::chooseNextRead() { // This method does the arbitration between read requests. The // chosen packet is simply moved to the head of the queue. The // other methods know that this is the place to look. For example, // with FCFS, this method does nothing if (readQueue.empty()) { DPRINTF(DRAM, "No read request to select\n"); return false; } // If there is only one request then there is nothing left to do if (readQueue.size() == 1) return true; if (memSchedPolicy == Enums::fcfs) { // Do nothing, since the request to serve is already the first // one in the read queue } else if (memSchedPolicy == Enums::frfcfs) { // Only determine this when needed uint64_t earliest_banks = 0; for (auto i = readQueue.begin(); i != readQueue.end() ; ++i) { DRAMPacket* dram_pkt = *i; const Bank& bank = dram_pkt->bankRef; // Check if it is a row hit if (bank.openRow == dram_pkt->row) { DPRINTF(DRAM, "Row buffer hit\n"); readQueue.erase(i); readQueue.push_front(dram_pkt); break; } else { // No row hit, go for first ready if (earliest_banks == 0) earliest_banks = minBankFreeAt(readQueue); // Bank is ready or is the first available bank if (bank.freeAt <= curTick() || bits(earliest_banks, dram_pkt->bankId, dram_pkt->bankId)) { readQueue.erase(i); readQueue.push_front(dram_pkt); break; } } } } else panic("No scheduling policy chosen!\n"); DPRINTF(DRAM, "Selected next read request\n"); return true; } void SimpleDRAM::accessAndRespond(PacketPtr pkt, Tick static_latency) { DPRINTF(DRAM, "Responding to Address %lld.. ",pkt->getAddr()); bool needsResponse = pkt->needsResponse(); // do the actual memory access which also turns the packet into a // response access(pkt); // turn packet around to go back to requester if response expected if (needsResponse) { // access already turned the packet into a response assert(pkt->isResponse()); // @todo someone should pay for this pkt->busFirstWordDelay = pkt->busLastWordDelay = 0; // queue the packet in the response queue to be sent out after // the static latency has passed port.schedTimingResp(pkt, curTick() + static_latency); } else { // @todo the packet is going to be deleted, and the DRAMPacket // is still having a pointer to it pendingDelete.push_back(pkt); } DPRINTF(DRAM, "Done\n"); return; } pair SimpleDRAM::estimateLatency(DRAMPacket* dram_pkt, Tick inTime) { // If a request reaches a bank at tick 'inTime', how much time // *after* that does it take to finish the request, depending // on bank status and page open policy. Note that this method // considers only the time taken for the actual read or write // to complete, NOT any additional time thereafter for tRAS or // tRP. Tick accLat = 0; Tick bankLat = 0; rowHitFlag = false; Tick potentialActTick; const Bank& bank = dram_pkt->bankRef; // open-page policy if (pageMgmt == Enums::open || pageMgmt == Enums::open_adaptive) { if (bank.openRow == dram_pkt->row) { // When we have a row-buffer hit, // we don't care about tRAS having expired or not, // but do care about bank being free for access rowHitFlag = true; // When a series of requests arrive to the same row, // DDR systems are capable of streaming data continuously // at maximum bandwidth (subject to tCCD). Here, we approximate // this condition, and assume that if whenever a bank is already // busy and a new request comes in, it can be completed with no // penalty beyond waiting for the existing read to complete. if (bank.freeAt > inTime) { accLat += bank.freeAt - inTime; bankLat += 0; } else { // CAS latency only accLat += tCL; bankLat += tCL; } } else { // Row-buffer miss, need to close existing row // once tRAS has expired, then open the new one, // then add cas latency. Tick freeTime = std::max(bank.tRASDoneAt, bank.freeAt); if (freeTime > inTime) accLat += freeTime - inTime; // If the there is no open row (open adaptive), then there // is no precharge delay, otherwise go with tRP Tick precharge_delay = bank.openRow == -1 ? 0 : tRP; //The bank is free, and you may be able to activate potentialActTick = inTime + accLat + precharge_delay; if (potentialActTick < bank.actAllowedAt) accLat += bank.actAllowedAt - potentialActTick; accLat += precharge_delay + tRCD + tCL; bankLat += precharge_delay + tRCD + tCL; } } else if (pageMgmt == Enums::close) { // With a close page policy, no notion of // bank.tRASDoneAt if (bank.freeAt > inTime) accLat += bank.freeAt - inTime; //The bank is free, and you may be able to activate potentialActTick = inTime + accLat; if (potentialActTick < bank.actAllowedAt) accLat += bank.actAllowedAt - potentialActTick; // page already closed, simply open the row, and // add cas latency accLat += tRCD + tCL; bankLat += tRCD + tCL; } else panic("No page management policy chosen\n"); DPRINTF(DRAM, "Returning < %lld, %lld > from estimateLatency()\n", bankLat, accLat); return make_pair(bankLat, accLat); } void SimpleDRAM::processNextReqEvent() { scheduleNextReq(); } void SimpleDRAM::recordActivate(Tick act_tick, uint8_t rank, uint8_t bank) { assert(0 <= rank && rank < ranksPerChannel); assert(actTicks[rank].size() == activationLimit); DPRINTF(DRAM, "Activate at tick %d\n", act_tick); // start by enforcing tRRD for(int i = 0; i < banksPerRank; i++) { // next activate must not happen before tRRD banks[rank][i].actAllowedAt = act_tick + tRRD; } // tRC should be added to activation tick of the bank currently accessed, // where tRC = tRAS + tRP, this is just for a check as actAllowedAt for same // bank is already captured by bank.freeAt and bank.tRASDoneAt banks[rank][bank].actAllowedAt = act_tick + tRAS + tRP; // next, we deal with tXAW, if the activation limit is disabled // then we are done if (actTicks[rank].empty()) return; // sanity check if (actTicks[rank].back() && (act_tick - actTicks[rank].back()) < tXAW) { // @todo For now, stick with a warning warn("Got %d activates in window %d (%d - %d) which is smaller " "than %d\n", activationLimit, act_tick - actTicks[rank].back(), act_tick, actTicks[rank].back(), tXAW); } // shift the times used for the book keeping, the last element // (highest index) is the oldest one and hence the lowest value actTicks[rank].pop_back(); // record an new activation (in the future) actTicks[rank].push_front(act_tick); // cannot activate more than X times in time window tXAW, push the // next one (the X + 1'st activate) to be tXAW away from the // oldest in our window of X if (actTicks[rank].back() && (act_tick - actTicks[rank].back()) < tXAW) { DPRINTF(DRAM, "Enforcing tXAW with X = %d, next activate no earlier " "than %d\n", activationLimit, actTicks[rank].back() + tXAW); for(int j = 0; j < banksPerRank; j++) // next activate must not happen before end of window banks[rank][j].actAllowedAt = actTicks[rank].back() + tXAW; } } void SimpleDRAM::doDRAMAccess(DRAMPacket* dram_pkt) { DPRINTF(DRAM, "Timing access to addr %lld, rank/bank/row %d %d %d\n", dram_pkt->addr, dram_pkt->rank, dram_pkt->bank, dram_pkt->row); // estimate the bank and access latency pair lat = estimateLatency(dram_pkt, curTick()); Tick bankLat = lat.first; Tick accessLat = lat.second; Tick actTick; // This request was woken up at this time based on a prior call // to estimateLatency(). However, between then and now, both the // accessLatency and/or busBusyUntil may have changed. We need // to correct for that. Tick addDelay = (curTick() + accessLat < busBusyUntil) ? busBusyUntil - (curTick() + accessLat) : 0; Bank& bank = dram_pkt->bankRef; // Update bank state if (pageMgmt == Enums::open || pageMgmt == Enums::open_adaptive) { bank.openRow = dram_pkt->row; bank.freeAt = curTick() + addDelay + accessLat; bank.bytesAccessed += burstSize; // If you activated a new row do to this access, the next access // will have to respect tRAS for this bank. if (!rowHitFlag) { // any waiting for banks account for in freeAt actTick = bank.freeAt - tCL - tRCD; bank.tRASDoneAt = actTick + tRAS; recordActivate(actTick, dram_pkt->rank, dram_pkt->bank); // sample the number of bytes accessed and reset it as // we are now closing this row bytesPerActivate.sample(bank.bytesAccessed); bank.bytesAccessed = 0; } if (pageMgmt == Enums::open_adaptive) { // a twist on the open page policy is to not blindly keep the // page open, but close it if there are no row hits, and there // are bank conflicts in the queue bool got_more_hits = false; bool got_bank_conflict = false; // either look at the read queue or write queue const deque& queue = dram_pkt->isRead ? readQueue : writeQueue; auto p = queue.begin(); // make sure we are not considering the packet that we are // currently dealing with (which is the head of the queue) ++p; // keep on looking until we have found both or reached // the end while (!(got_more_hits && got_bank_conflict) && p != queue.end()) { bool same_rank_bank = (dram_pkt->rank == (*p)->rank) && (dram_pkt->bank == (*p)->bank); bool same_row = dram_pkt->row == (*p)->row; got_more_hits |= same_rank_bank && same_row; got_bank_conflict |= same_rank_bank && !same_row; ++p; } // auto pre-charge if (!got_more_hits && got_bank_conflict) { bank.openRow = -1; bank.freeAt = std::max(bank.freeAt, bank.tRASDoneAt) + tRP; } } DPRINTF(DRAM, "doDRAMAccess::bank.freeAt is %lld\n", bank.freeAt); } else if (pageMgmt == Enums::close) { actTick = curTick() + addDelay + accessLat - tRCD - tCL; recordActivate(actTick, dram_pkt->rank, dram_pkt->bank); // If the DRAM has a very quick tRAS, bank can be made free // after consecutive tCL,tRCD,tRP times. In general, however, // an additional wait is required to respect tRAS. bank.freeAt = std::max(actTick + tRAS + tRP, actTick + tRCD + tCL + tRP); DPRINTF(DRAM, "doDRAMAccess::bank.freeAt is %lld\n", bank.freeAt); bytesPerActivate.sample(burstSize); } else panic("No page management policy chosen\n"); // Update request parameters dram_pkt->readyTime = curTick() + addDelay + accessLat + tBURST; DPRINTF(DRAM, "Req %lld: curtick is %lld accessLat is %d " \ "readytime is %lld busbusyuntil is %lld. " \ "Scheduling at readyTime\n", dram_pkt->addr, curTick(), accessLat, dram_pkt->readyTime, busBusyUntil); // Make sure requests are not overlapping on the databus assert (dram_pkt->readyTime - busBusyUntil >= tBURST); // Update bus state busBusyUntil = dram_pkt->readyTime; DPRINTF(DRAM,"Access time is %lld\n", dram_pkt->readyTime - dram_pkt->entryTime); if (rowHitFlag) { if(dram_pkt->isRead) readRowHits++; else writeRowHits++; } // Update the minimum timing between the requests newTime = (busBusyUntil > tRP + tRCD + tCL) ? std::max(busBusyUntil - (tRP + tRCD + tCL), curTick()) : curTick(); // At this point, commonality between reads and writes ends. // For writes, we are done since we long ago responded to the // requestor. We also don't care about stats for writes. For // reads, we still need to figure out respoding to the requestor, // and capture stats. if (!dram_pkt->isRead) { return; } // Update stats totMemAccLat += dram_pkt->readyTime - dram_pkt->entryTime; totBankLat += bankLat; totBusLat += tBURST; totQLat += dram_pkt->readyTime - dram_pkt->entryTime - bankLat - tBURST; // At this point we're done dealing with the request // It will be moved to a separate response queue with a // correct readyTime, and eventually be sent back at that //time moveToRespQ(); // Schedule the next read event if (!nextReqEvent.scheduled() && !stopReads){ schedule(nextReqEvent, newTime); } else { if (newTime < nextReqEvent.when()) reschedule(nextReqEvent, newTime); } } void SimpleDRAM::moveToRespQ() { // Remove from read queue DRAMPacket* dram_pkt = readQueue.front(); readQueue.pop_front(); // sanity check assert(dram_pkt->size <= burstSize); // Insert into response queue sorted by readyTime // It will be sent back to the requestor at its // readyTime if (respQueue.empty()) { respQueue.push_front(dram_pkt); assert(!respondEvent.scheduled()); assert(dram_pkt->readyTime >= curTick()); schedule(respondEvent, dram_pkt->readyTime); } else { bool done = false; auto i = respQueue.begin(); while (!done && i != respQueue.end()) { if ((*i)->readyTime > dram_pkt->readyTime) { respQueue.insert(i, dram_pkt); done = true; } ++i; } if (!done) respQueue.push_back(dram_pkt); assert(respondEvent.scheduled()); if (respQueue.front()->readyTime < respondEvent.when()) { assert(respQueue.front()->readyTime >= curTick()); reschedule(respondEvent, respQueue.front()->readyTime); } } } void SimpleDRAM::scheduleNextReq() { DPRINTF(DRAM, "Reached scheduleNextReq()\n"); // Figure out which read request goes next, and move it to the // front of the read queue if (!chooseNextRead()) { // In the case there is no read request to go next, see if we // are asked to drain, and if so trigger writes, this also // ensures that if we hit the write limit we will do this // multiple times until we are completely drained if (drainManager && !writeQueue.empty() && !writeEvent.scheduled()) triggerWrites(); } else { doDRAMAccess(readQueue.front()); } } Tick SimpleDRAM::maxBankFreeAt() const { Tick banksFree = 0; for(int i = 0; i < ranksPerChannel; i++) for(int j = 0; j < banksPerRank; j++) banksFree = std::max(banks[i][j].freeAt, banksFree); return banksFree; } uint64_t SimpleDRAM::minBankFreeAt(const deque& queue) const { uint64_t bank_mask = 0; Tick freeAt = MaxTick; // detemrine if we have queued transactions targetting the // bank in question vector got_waiting(ranksPerChannel * banksPerRank, false); for (auto p = queue.begin(); p != queue.end(); ++p) { got_waiting[(*p)->bankId] = true; } for (int i = 0; i < ranksPerChannel; i++) { for (int j = 0; j < banksPerRank; j++) { // if we have waiting requests for the bank, and it is // amongst the first available, update the mask if (got_waiting[i * banksPerRank + j] && banks[i][j].freeAt <= freeAt) { // reset bank mask if new minimum is found if (banks[i][j].freeAt < freeAt) bank_mask = 0; // set the bit corresponding to the available bank uint8_t bit_index = i * ranksPerChannel + j; replaceBits(bank_mask, bit_index, bit_index, 1); freeAt = banks[i][j].freeAt; } } } return bank_mask; } void SimpleDRAM::processRefreshEvent() { DPRINTF(DRAM, "Refreshing at tick %ld\n", curTick()); Tick banksFree = std::max(curTick(), maxBankFreeAt()) + tRFC; for(int i = 0; i < ranksPerChannel; i++) for(int j = 0; j < banksPerRank; j++) banks[i][j].freeAt = banksFree; schedule(refreshEvent, curTick() + tREFI); } void SimpleDRAM::regStats() { using namespace Stats; AbstractMemory::regStats(); readReqs .name(name() + ".readReqs") .desc("Total number of read requests accepted by DRAM controller"); writeReqs .name(name() + ".writeReqs") .desc("Total number of write requests accepted by DRAM controller"); readBursts .name(name() + ".readBursts") .desc("Total number of DRAM read bursts. " "Each DRAM read request translates to either one or multiple " "DRAM read bursts"); writeBursts .name(name() + ".writeBursts") .desc("Total number of DRAM write bursts. " "Each DRAM write request translates to either one or multiple " "DRAM write bursts"); servicedByWrQ .name(name() + ".servicedByWrQ") .desc("Number of DRAM read bursts serviced by write Q"); neitherReadNorWrite .name(name() + ".neitherReadNorWrite") .desc("Reqs where no action is needed"); perBankRdReqs .init(banksPerRank * ranksPerChannel) .name(name() + ".perBankRdReqs") .desc("Track reads on a per bank basis"); perBankWrReqs .init(banksPerRank * ranksPerChannel) .name(name() + ".perBankWrReqs") .desc("Track writes on a per bank basis"); avgRdQLen .name(name() + ".avgRdQLen") .desc("Average read queue length over time") .precision(2); avgWrQLen .name(name() + ".avgWrQLen") .desc("Average write queue length over time") .precision(2); totQLat .name(name() + ".totQLat") .desc("Total cycles spent in queuing delays"); totBankLat .name(name() + ".totBankLat") .desc("Total cycles spent in bank access"); totBusLat .name(name() + ".totBusLat") .desc("Total cycles spent in databus access"); totMemAccLat .name(name() + ".totMemAccLat") .desc("Sum of mem lat for all requests"); avgQLat .name(name() + ".avgQLat") .desc("Average queueing delay per request") .precision(2); avgQLat = totQLat / (readBursts - servicedByWrQ); avgBankLat .name(name() + ".avgBankLat") .desc("Average bank access latency per request") .precision(2); avgBankLat = totBankLat / (readBursts - servicedByWrQ); avgBusLat .name(name() + ".avgBusLat") .desc("Average bus latency per request") .precision(2); avgBusLat = totBusLat / (readBursts - servicedByWrQ); avgMemAccLat .name(name() + ".avgMemAccLat") .desc("Average memory access latency") .precision(2); avgMemAccLat = totMemAccLat / (readBursts - servicedByWrQ); numRdRetry .name(name() + ".numRdRetry") .desc("Number of times rd buffer was full causing retry"); numWrRetry .name(name() + ".numWrRetry") .desc("Number of times wr buffer was full causing retry"); readRowHits .name(name() + ".readRowHits") .desc("Number of row buffer hits during reads"); writeRowHits .name(name() + ".writeRowHits") .desc("Number of row buffer hits during writes"); readRowHitRate .name(name() + ".readRowHitRate") .desc("Row buffer hit rate for reads") .precision(2); readRowHitRate = (readRowHits / (readBursts - servicedByWrQ)) * 100; writeRowHitRate .name(name() + ".writeRowHitRate") .desc("Row buffer hit rate for writes") .precision(2); writeRowHitRate = (writeRowHits / writeBursts) * 100; readPktSize .init(ceilLog2(burstSize) + 1) .name(name() + ".readPktSize") .desc("Categorize read packet sizes"); writePktSize .init(ceilLog2(burstSize) + 1) .name(name() + ".writePktSize") .desc("Categorize write packet sizes"); rdQLenPdf .init(readBufferSize) .name(name() + ".rdQLenPdf") .desc("What read queue length does an incoming req see"); wrQLenPdf .init(writeBufferSize) .name(name() + ".wrQLenPdf") .desc("What write queue length does an incoming req see"); bytesPerActivate .init(rowBufferSize) .name(name() + ".bytesPerActivate") .desc("Bytes accessed per row activation") .flags(nozero); bytesRead .name(name() + ".bytesRead") .desc("Total number of bytes read from memory"); bytesWritten .name(name() + ".bytesWritten") .desc("Total number of bytes written to memory"); bytesConsumedRd .name(name() + ".bytesConsumedRd") .desc("bytesRead derated as per pkt->getSize()"); bytesConsumedWr .name(name() + ".bytesConsumedWr") .desc("bytesWritten derated as per pkt->getSize()"); avgRdBW .name(name() + ".avgRdBW") .desc("Average achieved read bandwidth in MB/s") .precision(2); avgRdBW = (bytesRead / 1000000) / simSeconds; avgWrBW .name(name() + ".avgWrBW") .desc("Average achieved write bandwidth in MB/s") .precision(2); avgWrBW = (bytesWritten / 1000000) / simSeconds; avgConsumedRdBW .name(name() + ".avgConsumedRdBW") .desc("Average consumed read bandwidth in MB/s") .precision(2); avgConsumedRdBW = (bytesConsumedRd / 1000000) / simSeconds; avgConsumedWrBW .name(name() + ".avgConsumedWrBW") .desc("Average consumed write bandwidth in MB/s") .precision(2); avgConsumedWrBW = (bytesConsumedWr / 1000000) / simSeconds; peakBW .name(name() + ".peakBW") .desc("Theoretical peak bandwidth in MB/s") .precision(2); peakBW = (SimClock::Frequency / tBURST) * burstSize / 1000000; busUtil .name(name() + ".busUtil") .desc("Data bus utilization in percentage") .precision(2); busUtil = (avgRdBW + avgWrBW) / peakBW * 100; totGap .name(name() + ".totGap") .desc("Total gap between requests"); avgGap .name(name() + ".avgGap") .desc("Average gap between requests") .precision(2); avgGap = totGap / (readReqs + writeReqs); } void SimpleDRAM::recvFunctional(PacketPtr pkt) { // rely on the abstract memory functionalAccess(pkt); } BaseSlavePort& SimpleDRAM::getSlavePort(const string &if_name, PortID idx) { if (if_name != "port") { return MemObject::getSlavePort(if_name, idx); } else { return port; } } unsigned int SimpleDRAM::drain(DrainManager *dm) { unsigned int count = port.drain(dm); // if there is anything in any of our internal queues, keep track // of that as well if (!(writeQueue.empty() && readQueue.empty() && respQueue.empty())) { DPRINTF(Drain, "DRAM controller not drained, write: %d, read: %d," " resp: %d\n", writeQueue.size(), readQueue.size(), respQueue.size()); ++count; drainManager = dm; // the only part that is not drained automatically over time // is the write queue, thus trigger writes if there are any // waiting and no reads waiting, otherwise wait until the // reads are done if (readQueue.empty() && !writeQueue.empty() && !writeEvent.scheduled()) triggerWrites(); } if (count) setDrainState(Drainable::Draining); else setDrainState(Drainable::Drained); return count; } SimpleDRAM::MemoryPort::MemoryPort(const std::string& name, SimpleDRAM& _memory) : QueuedSlavePort(name, &_memory, queue), queue(_memory, *this), memory(_memory) { } AddrRangeList SimpleDRAM::MemoryPort::getAddrRanges() const { AddrRangeList ranges; ranges.push_back(memory.getAddrRange()); return ranges; } void SimpleDRAM::MemoryPort::recvFunctional(PacketPtr pkt) { pkt->pushLabel(memory.name()); if (!queue.checkFunctional(pkt)) { // Default implementation of SimpleTimingPort::recvFunctional() // calls recvAtomic() and throws away the latency; we can save a // little here by just not calculating the latency. memory.recvFunctional(pkt); } pkt->popLabel(); } Tick SimpleDRAM::MemoryPort::recvAtomic(PacketPtr pkt) { return memory.recvAtomic(pkt); } bool SimpleDRAM::MemoryPort::recvTimingReq(PacketPtr pkt) { // pass it to the memory controller return memory.recvTimingReq(pkt); } SimpleDRAM* SimpleDRAMParams::create() { return new SimpleDRAM(this); }