/*
* 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
*/
#include "base/trace.hh"
#include "debug/Drain.hh"
#include "debug/DRAM.hh"
#include "debug/DRAMWR.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), actTicks(p->activation_limit, 0),
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),
writeThresholdPerc(p->write_thresh_perc),
tWTR(p->tWTR), tBURST(p->tBURST),
tRCD(p->tRCD), tCL(p->tCL), tRP(p->tRP),
tRFC(p->tRFC), tREFI(p->tREFI),
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)
{
// create the bank states based on the dimensions of the ranks and
// banks
banks.resize(ranksPerChannel);
for (size_t c = 0; c < ranksPerChannel; ++c) {
banks[c].resize(banksPerRank);
}
// round the write threshold percent to a whole number of entries
// in the buffer
writeThreshold = writeBufferSize * writeThresholdPerc / 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)
{
// 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;
uint16_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
return new DRAMPacket(pkt, rank, bank, row, 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);
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
uint32_t bank_id = banksPerRank * dram_pkt->rank + dram_pkt->bank;
assert(bank_id < ranksPerChannel * banksPerRank);
perBankRdReqs[bank_id]++;
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());
uint32_t numWritesThisTime = 0;
DPRINTF(DRAMWR, "Beginning DRAM Writes\n");
Tick temp1 M5_VAR_USED = std::max(curTick(), busBusyUntil);
Tick temp2 M5_VAR_USED = std::max(curTick(), maxBankFreeAt());
// @todo: are there any dangers with the untimed while loop?
while (!writeQueue.empty()) {
if (numWritesThisTime > writeThreshold) {
DPRINTF(DRAMWR, "Hit write threshold %d\n", writeThreshold);
break;
}
chooseNextWrite();
DRAMPacket* dram_pkt = writeQueue.front();
// sanity check
assert(dram_pkt->size <= burstSize);
// What's the earliest the request can be put on the bus
Tick schedTime = std::max(curTick(), busBusyUntil);
DPRINTF(DRAMWR, "Asking for latency estimate at %lld\n",
schedTime + tBURST);
pair<Tick, Tick> lat = estimateLatency(dram_pkt, schedTime + tBURST);
Tick accessLat = lat.second;
// look at the rowHitFlag set by estimateLatency
if (rowHitFlag)
writeRowHits++;
Bank& bank = dram_pkt->bank_ref;
if (pageMgmt == Enums::open) {
bank.openRow = dram_pkt->row;
bank.freeAt = schedTime + tBURST + std::max(accessLat, tCL);
busBusyUntil = bank.freeAt - tCL;
bank.bytesAccessed += burstSize;
if (!rowHitFlag) {
bank.tRASDoneAt = bank.freeAt + tRP;
recordActivate(bank.freeAt - tCL - tRCD);
busBusyUntil = bank.freeAt - tCL - tRCD;
// sample the number of bytes accessed and reset it as
// we are now closing this row
bytesPerActivate.sample(bank.bytesAccessed);
bank.bytesAccessed = 0;
}
} else if (pageMgmt == Enums::close) {
bank.freeAt = schedTime + tBURST + accessLat + tRP + tRP;
// Work backwards from bank.freeAt to determine activate time
recordActivate(bank.freeAt - tRP - tRP - tCL - tRCD);
busBusyUntil = bank.freeAt - tRP - tRP - tCL - tRCD;
DPRINTF(DRAMWR, "processWriteEvent::bank.freeAt for "
"banks_id %d is %lld\n",
dram_pkt->rank * banksPerRank + dram_pkt->bank,
bank.freeAt);
bytesPerActivate.sample(burstSize);
} else
panic("Unknown page management policy chosen\n");
DPRINTF(DRAMWR, "Done writing to address %lld\n", dram_pkt->addr);
DPRINTF(DRAMWR, "schedtime is %lld, tBURST is %lld, "
"busbusyuntil is %lld\n",
schedTime, tBURST, busBusyUntil);
writeQueue.pop_front();
delete dram_pkt;
numWritesThisTime++;
}
DPRINTF(DRAMWR, "Completed %d writes, bus busy for %lld ticks,"\
"banks busy for %lld ticks\n", numWritesThisTime,
busBusyUntil - temp1, maxBankFreeAt() - temp2);
// Update stats
avgWrQLen = writeQueue.size();
// turn the bus back around for reads again
busBusyUntil += tWTR;
stopReads = false;
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;
}
// Once you're done emptying the write queue, check if there's
// anything in the read queue, and call schedule if required. The
// retry above could already have caused it to be scheduled, so
// first check
if (!nextReqEvent.scheduled())
schedule(nextReqEvent, busBusyUntil);
}
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);
assert(writeQueue.size() < writeBufferSize);
wrQLenPdf[writeQueue.size()]++;
DPRINTF(DRAM, "Adding to write queue\n");
writeQueue.push_back(dram_pkt);
// Update stats
uint32_t bank_id = banksPerRank * dram_pkt->rank + dram_pkt->bank;
assert(bank_id < ranksPerChannel * banksPerRank);
perBankWrReqs[bank_id]++;
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() > writeThreshold && !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" : "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, writeThreshold,
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(DRAMWR, "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) {
auto i = writeQueue.begin();
bool foundRowHit = false;
while (!foundRowHit && i != writeQueue.end()) {
DRAMPacket* dram_pkt = *i;
const Bank& bank = dram_pkt->bank_ref;
if (bank.openRow == dram_pkt->row) { //FR part
DPRINTF(DRAMWR, "Write row buffer hit\n");
writeQueue.erase(i);
writeQueue.push_front(dram_pkt);
foundRowHit = true;
} else { //FCFS part
;
}
++i;
}
} else
panic("No scheduling policy chosen\n");
DPRINTF(DRAMWR, "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) {
for (auto i = readQueue.begin(); i != readQueue.end() ; ++i) {
DRAMPacket* dram_pkt = *i;
const Bank& bank = dram_pkt->bank_ref;
// Check if it is a row hit
if (bank.openRow == dram_pkt->row) { //FR part
DPRINTF(DRAM, "Row buffer hit\n");
readQueue.erase(i);
readQueue.push_front(dram_pkt);
break;
} else { //FCFS part
;
}
}
} 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<Tick, Tick>
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;
const Bank& bank = dram_pkt->bank_ref;
if (pageMgmt == Enums::open) { // open-page policy
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;
if (bank.freeAt < inTime) {
// CAS latency only
accLat += tCL;
bankLat += tCL;
} else {
accLat += 0;
bankLat += 0;
}
} 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;
accLat += tRP + tRCD + tCL;
bankLat += tRP + 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;
// 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)
{
assert(actTicks.size() == activationLimit);
DPRINTF(DRAM, "Activate at tick %d\n", act_tick);
// if the activation limit is disabled then we are done
if (actTicks.empty())
return;
// sanity check
if (actTicks.back() && (act_tick - actTicks.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.back(),
act_tick, actTicks.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.pop_back();
// record an new activation (in the future)
actTicks.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.back() && (act_tick - actTicks.back()) < tXAW) {
DPRINTF(DRAM, "Enforcing tXAW with X = %d, next activate no earlier "
"than %d\n", activationLimit, actTicks.back() + tXAW);
for(int i = 0; i < ranksPerChannel; i++)
for(int j = 0; j < banksPerRank; j++)
// next activate must not happen before end of window
banks[i][j].freeAt = std::max(banks[i][j].freeAt,
actTicks.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<Tick, Tick> lat = estimateLatency(dram_pkt, curTick());
Tick bankLat = lat.first;
Tick accessLat = lat.second;
// 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->bank_ref;
// Update bank state
if (pageMgmt == Enums::open) {
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. Assume tRAS ~= 3 * tRP.
// Also need to account for t_XAW
if (!rowHitFlag) {
bank.tRASDoneAt = bank.freeAt + tRP;
recordActivate(bank.freeAt - tCL - tRCD); //since this is open page,
//no tRP by default
// sample the number of bytes accessed and reset it as
// we are now closing this row
bytesPerActivate.sample(bank.bytesAccessed);
bank.bytesAccessed = 0;
}
} else if (pageMgmt == Enums::close) { // accounting for tRAS also
// assuming that tRAS ~= 3 * tRP, and tRC ~= 4 * tRP, as is common
// (refer Jacob/Ng/Wang and Micron datasheets)
bank.freeAt = curTick() + addDelay + accessLat + tRP + tRP;
recordActivate(bank.freeAt - tRP - tRP - tCL - tRCD); //essentially (freeAt - tRC)
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);
// Update stats
totMemAccLat += dram_pkt->readyTime - dram_pkt->entryTime;
totBankLat += bankLat;
totBusLat += tBURST;
totQLat += dram_pkt->readyTime - dram_pkt->entryTime - bankLat - tBURST;
if (rowHitFlag)
readRowHits++;
// 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();
// The absolute soonest you have to start thinking about the
// next request is the longest access time that can occur before
// busBusyUntil. Assuming you need to meet tRAS, then precharge,
// open a new row, and access, it is ~4*tRCD.
Tick newTime = (busBusyUntil > 4 * tRCD) ?
std::max(busBusyUntil - 4 * tRCD, curTick()) :
curTick();
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;
}
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);
}