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gem5 / public / gem5 / 60e55ecef8310fc861e1effb0b1776c732abeacc / . / src / mem / mem_interface.cc
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/*
* Copyright (c) 2010-2020 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.
*/
#include "mem/mem_interface.hh"
#include "base/bitfield.hh"
#include "base/cprintf.hh"
#include "base/trace.hh"
#include "debug/DRAM.hh"
#include "debug/DRAMPower.hh"
#include "debug/DRAMState.hh"
#include "debug/NVM.hh"
#include "sim/system.hh"
namespace gem5
{
using namespace Data;
namespace memory
{
MemInterface::MemInterface(const MemInterfaceParams &_p)
: AbstractMemory(_p),
addrMapping(_p.addr_mapping),
burstSize((_p.devices_per_rank * _p.burst_length *
_p.device_bus_width) / 8),
deviceSize(_p.device_size),
deviceRowBufferSize(_p.device_rowbuffer_size),
devicesPerRank(_p.devices_per_rank),
rowBufferSize(devicesPerRank * deviceRowBufferSize),
burstsPerRowBuffer(rowBufferSize / burstSize),
burstsPerStripe(range.interleaved() ?
range.granularity() / burstSize : 1),
ranksPerChannel(_p.ranks_per_channel),
banksPerRank(_p.banks_per_rank), rowsPerBank(0),
tCK(_p.tCK), tCS(_p.tCS), tBURST(_p.tBURST),
tRTW(_p.tRTW),
tWTR(_p.tWTR),
readBufferSize(_p.read_buffer_size),
writeBufferSize(_p.write_buffer_size)
{}
void
MemInterface::setCtrl(MemCtrl* _ctrl, unsigned int command_window)
{
ctrl = _ctrl;
maxCommandsPerWindow = command_window / tCK;
}
MemPacket*
MemInterface::decodePacket(const PacketPtr pkt, Addr pkt_addr,
unsigned size, bool is_read, bool is_dram)
{
// decode the address based on the address mapping scheme, with
// Ro, Ra, Co, Ba and Ch denoting row, rank, column, bank and
// channel, respectively
uint8_t rank;
uint8_t bank;
// use a 64-bit unsigned during the computations as the row is
// always the top bits, and check before creating the packet
uint64_t row;
// Get packed address, starting at 0
Addr addr = getCtrlAddr(pkt_addr);
// truncate the address to a memory burst, which makes it unique to
// a specific buffer, row, bank, rank and channel
addr = addr / burstSize;
// we have removed the lowest order address bits that denote the
// position within the column
if (addrMapping == enums::RoRaBaChCo || addrMapping == enums::RoRaBaCoCh) {
// the lowest order bits denote the column to ensure that
// sequential cache lines occupy the same row
addr = addr / burstsPerRowBuffer;
// 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, no need to remove them from addr
row = addr % rowsPerBank;
} else if (addrMapping == enums::RoCoRaBaCh) {
// with emerging technologies, could have small page size with
// interleaving granularity greater than row buffer
if (burstsPerStripe > burstsPerRowBuffer) {
// remove column bits which are a subset of burstsPerStripe
addr = addr / burstsPerRowBuffer;
} else {
// remove lower column bits below channel bits
addr = addr / burstsPerStripe;
}
// 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 higher-order column bites
if (burstsPerStripe < burstsPerRowBuffer) {
addr = addr / (burstsPerRowBuffer / burstsPerStripe);
}
// lastly, get the row bits, no need to remove them from addr
row = addr % rowsPerBank;
} else
panic("Unknown address mapping policy chosen!");
assert(rank < ranksPerChannel);
assert(bank < banksPerRank);
assert(row < rowsPerBank);
assert(row < Bank::NO_ROW);
DPRINTF(DRAM, "Address: %#x Rank %d Bank %d Row %d\n",
pkt_addr, rank, bank, row);
// create the corresponding memory 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 MemPacket(pkt, is_read, is_dram, rank, bank, row, bank_id,
pkt_addr, size);
}
std::pair<MemPacketQueue::iterator, Tick>
DRAMInterface::chooseNextFRFCFS(MemPacketQueue& queue, Tick min_col_at) const
{
std::vector<uint32_t> earliest_banks(ranksPerChannel, 0);
// Has minBankPrep been called to populate earliest_banks?
bool filled_earliest_banks = false;
// can the PRE/ACT sequence be done without impacting utlization?
bool hidden_bank_prep = false;
// search for seamless row hits first, if no seamless row hit is
// found then determine if there are other packets that can be issued
// without incurring additional bus delay due to bank timing
// Will select closed rows first to enable more open row possibilies
// in future selections
bool found_hidden_bank = false;
// remember if we found a row hit, not seamless, but bank prepped
// and ready
bool found_prepped_pkt = false;
// if we have no row hit, prepped or not, and no seamless packet,
// just go for the earliest possible
bool found_earliest_pkt = false;
Tick selected_col_at = MaxTick;
auto selected_pkt_it = queue.end();
for (auto i = queue.begin(); i != queue.end() ; ++i) {
MemPacket* pkt = *i;
// select optimal DRAM packet in Q
if (pkt->isDram()) {
const Bank& bank = ranks[pkt->rank]->banks[pkt->bank];
const Tick col_allowed_at = pkt->isRead() ? bank.rdAllowedAt :
bank.wrAllowedAt;
DPRINTF(DRAM, "%s checking DRAM packet in bank %d, row %d\n",
__func__, pkt->bank, pkt->row);
// check if rank is not doing a refresh and thus is available,
// if not, jump to the next packet
if (burstReady(pkt)) {
DPRINTF(DRAM,
"%s bank %d - Rank %d available\n", __func__,
pkt->bank, pkt->rank);
// check if it is a row hit
if (bank.openRow == pkt->row) {
// no additional rank-to-rank or same bank-group
// delays, or we switched read/write and might as well
// go for the row hit
if (col_allowed_at <= min_col_at) {
// FCFS within the hits, giving priority to
// commands that can issue seamlessly, without
// additional delay, such as same rank accesses
// and/or different bank-group accesses
DPRINTF(DRAM, "%s Seamless buffer hit\n", __func__);
selected_pkt_it = i;
selected_col_at = col_allowed_at;
// no need to look through the remaining queue entries
break;
} else if (!found_hidden_bank && !found_prepped_pkt) {
// if we did not find a packet to a closed row that can
// issue the bank commands without incurring delay, and
// did not yet find a packet to a prepped row, remember
// the current one
selected_pkt_it = i;
selected_col_at = col_allowed_at;
found_prepped_pkt = true;
DPRINTF(DRAM, "%s Prepped row buffer hit\n", __func__);
}
} else if (!found_earliest_pkt) {
// if we have not initialised the bank status, do it
// now, and only once per scheduling decisions
if (!filled_earliest_banks) {
// determine entries with earliest bank delay
std::tie(earliest_banks, hidden_bank_prep) =
minBankPrep(queue, min_col_at);
filled_earliest_banks = true;
}
// bank is amongst first available banks
// minBankPrep will give priority to packets that can
// issue seamlessly
if (bits(earliest_banks[pkt->rank],
pkt->bank, pkt->bank)) {
found_earliest_pkt = true;
found_hidden_bank = hidden_bank_prep;
// give priority to packets that can issue
// bank commands 'behind the scenes'
// any additional delay if any will be due to
// col-to-col command requirements
if (hidden_bank_prep || !found_prepped_pkt) {
selected_pkt_it = i;
selected_col_at = col_allowed_at;
}
}
}
} else {
DPRINTF(DRAM, "%s bank %d - Rank %d not available\n", __func__,
pkt->bank, pkt->rank);
}
}
}
if (selected_pkt_it == queue.end()) {
DPRINTF(DRAM, "%s no available DRAM ranks found\n", __func__);
}
return std::make_pair(selected_pkt_it, selected_col_at);
}
void
DRAMInterface::activateBank(Rank& rank_ref, Bank& bank_ref,
Tick act_tick, uint32_t row)
{
assert(rank_ref.actTicks.size() == activationLimit);
// verify that we have command bandwidth to issue the activate
// if not, shift to next burst window
Tick act_at;
if (twoCycleActivate)
act_at = ctrl->verifyMultiCmd(act_tick, maxCommandsPerWindow, tAAD);
else
act_at = ctrl->verifySingleCmd(act_tick, maxCommandsPerWindow);
DPRINTF(DRAM, "Activate at tick %d\n", act_at);
// update the open row
assert(bank_ref.openRow == Bank::NO_ROW);
bank_ref.openRow = row;
// start counting anew, this covers both the case when we
// auto-precharged, and when this access is forced to
// precharge
bank_ref.bytesAccessed = 0;
bank_ref.rowAccesses = 0;
++rank_ref.numBanksActive;
assert(rank_ref.numBanksActive <= banksPerRank);
DPRINTF(DRAM, "Activate bank %d, rank %d at tick %lld, now got "
"%d active\n", bank_ref.bank, rank_ref.rank, act_at,
ranks[rank_ref.rank]->numBanksActive);
rank_ref.cmdList.push_back(Command(MemCommand::ACT, bank_ref.bank,
act_at));
DPRINTF(DRAMPower, "%llu,ACT,%d,%d\n", divCeil(act_at, tCK) -
timeStampOffset, bank_ref.bank, rank_ref.rank);
// The next access has to respect tRAS for this bank
bank_ref.preAllowedAt = act_at + tRAS;
// Respect the row-to-column command delay for both read and write cmds
bank_ref.rdAllowedAt = std::max(act_at + tRCD, bank_ref.rdAllowedAt);
bank_ref.wrAllowedAt = std::max(act_at + tRCD, bank_ref.wrAllowedAt);
// start by enforcing tRRD
for (int i = 0; i < banksPerRank; i++) {
// next activate to any bank in this rank must not happen
// before tRRD
if (bankGroupArch && (bank_ref.bankgr == rank_ref.banks[i].bankgr)) {
// bank group architecture requires longer delays between
// ACT commands within the same bank group. Use tRRD_L
// in this case
rank_ref.banks[i].actAllowedAt = std::max(act_at + tRRD_L,
rank_ref.banks[i].actAllowedAt);
} else {
// use shorter tRRD value when either
// 1) bank group architecture is not supportted
// 2) bank is in a different bank group
rank_ref.banks[i].actAllowedAt = std::max(act_at + tRRD,
rank_ref.banks[i].actAllowedAt);
}
}
// next, we deal with tXAW, if the activation limit is disabled
// then we directly schedule an activate power event
if (!rank_ref.actTicks.empty()) {
// sanity check
if (rank_ref.actTicks.back() &&
(act_at - rank_ref.actTicks.back()) < tXAW) {
panic("Got %d activates in window %d (%llu - %llu) which "
"is smaller than %llu\n", activationLimit, act_at -
rank_ref.actTicks.back(), act_at,
rank_ref.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
rank_ref.actTicks.pop_back();
// record an new activation (in the future)
rank_ref.actTicks.push_front(act_at);
// 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 (rank_ref.actTicks.back() &&
(act_at - rank_ref.actTicks.back()) < tXAW) {
DPRINTF(DRAM, "Enforcing tXAW with X = %d, next activate "
"no earlier than %llu\n", activationLimit,
rank_ref.actTicks.back() + tXAW);
for (int j = 0; j < banksPerRank; j++)
// next activate must not happen before end of window
rank_ref.banks[j].actAllowedAt =
std::max(rank_ref.actTicks.back() + tXAW,
rank_ref.banks[j].actAllowedAt);
}
}
// at the point when this activate takes place, make sure we
// transition to the active power state
if (!rank_ref.activateEvent.scheduled())
schedule(rank_ref.activateEvent, act_at);
else if (rank_ref.activateEvent.when() > act_at)
// move it sooner in time
reschedule(rank_ref.activateEvent, act_at);
}
void
DRAMInterface::prechargeBank(Rank& rank_ref, Bank& bank, Tick pre_tick,
bool auto_or_preall, bool trace)
{
// make sure the bank has an open row
assert(bank.openRow != Bank::NO_ROW);
// sample the bytes per activate here since we are closing
// the page
stats.bytesPerActivate.sample(bank.bytesAccessed);
bank.openRow = Bank::NO_ROW;
Tick pre_at = pre_tick;
if (auto_or_preall) {
// no precharge allowed before this one
bank.preAllowedAt = pre_at;
} else {
// Issuing an explicit PRE command
// Verify that we have command bandwidth to issue the precharge
// if not, shift to next burst window
pre_at = ctrl->verifySingleCmd(pre_tick, maxCommandsPerWindow);
// enforce tPPD
for (int i = 0; i < banksPerRank; i++) {
rank_ref.banks[i].preAllowedAt = std::max(pre_at + tPPD,
rank_ref.banks[i].preAllowedAt);
}
}
Tick pre_done_at = pre_at + tRP;
bank.actAllowedAt = std::max(bank.actAllowedAt, pre_done_at);
assert(rank_ref.numBanksActive != 0);
--rank_ref.numBanksActive;
DPRINTF(DRAM, "Precharging bank %d, rank %d at tick %lld, now got "
"%d active\n", bank.bank, rank_ref.rank, pre_at,
rank_ref.numBanksActive);
if (trace) {
rank_ref.cmdList.push_back(Command(MemCommand::PRE, bank.bank,
pre_at));
DPRINTF(DRAMPower, "%llu,PRE,%d,%d\n", divCeil(pre_at, tCK) -
timeStampOffset, bank.bank, rank_ref.rank);
}
// if we look at the current number of active banks we might be
// tempted to think the DRAM is now idle, however this can be
// undone by an activate that is scheduled to happen before we
// would have reached the idle state, so schedule an event and
// rather check once we actually make it to the point in time when
// the (last) precharge takes place
if (!rank_ref.prechargeEvent.scheduled()) {
schedule(rank_ref.prechargeEvent, pre_done_at);
// New event, increment count
++rank_ref.outstandingEvents;
} else if (rank_ref.prechargeEvent.when() < pre_done_at) {
reschedule(rank_ref.prechargeEvent, pre_done_at);
}
}
std::pair<Tick, Tick>
DRAMInterface::doBurstAccess(MemPacket* mem_pkt, Tick next_burst_at,
const std::vector<MemPacketQueue>& queue)
{
DPRINTF(DRAM, "Timing access to addr %#x, rank/bank/row %d %d %d\n",
mem_pkt->addr, mem_pkt->rank, mem_pkt->bank, mem_pkt->row);
// get the rank
Rank& rank_ref = *ranks[mem_pkt->rank];
assert(rank_ref.inRefIdleState());
// are we in or transitioning to a low-power state and have not scheduled
// a power-up event?
// if so, wake up from power down to issue RD/WR burst
if (rank_ref.inLowPowerState) {
assert(rank_ref.pwrState != PWR_SREF);
rank_ref.scheduleWakeUpEvent(tXP);
}
// get the bank
Bank& bank_ref = rank_ref.banks[mem_pkt->bank];
// for the state we need to track if it is a row hit or not
bool row_hit = true;
// Determine the access latency and update the bank state
if (bank_ref.openRow == mem_pkt->row) {
// nothing to do
} else {
row_hit = false;
// If there is a page open, precharge it.
if (bank_ref.openRow != Bank::NO_ROW) {
prechargeBank(rank_ref, bank_ref, std::max(bank_ref.preAllowedAt,
curTick()));
}
// next we need to account for the delay in activating the page
Tick act_tick = std::max(bank_ref.actAllowedAt, curTick());
// Record the activation and deal with all the global timing
// constraints caused be a new activation (tRRD and tXAW)
activateBank(rank_ref, bank_ref, act_tick, mem_pkt->row);
}
// respect any constraints on the command (e.g. tRCD or tCCD)
const Tick col_allowed_at = mem_pkt->isRead() ?
bank_ref.rdAllowedAt : bank_ref.wrAllowedAt;
// we need to wait until the bus is available before we can issue
// the command; need to ensure minimum bus delay requirement is met
Tick cmd_at = std::max({col_allowed_at, next_burst_at, curTick()});
// verify that we have command bandwidth to issue the burst
// if not, shift to next burst window
if (dataClockSync && ((cmd_at - rank_ref.lastBurstTick) > clkResyncDelay))
cmd_at = ctrl->verifyMultiCmd(cmd_at, maxCommandsPerWindow, tCK);
else
cmd_at = ctrl->verifySingleCmd(cmd_at, maxCommandsPerWindow);
// if we are interleaving bursts, ensure that
// 1) we don't double interleave on next burst issue
// 2) we are at an interleave boundary; if not, shift to next boundary
Tick burst_gap = tBURST_MIN;
if (burstInterleave) {
if (cmd_at == (rank_ref.lastBurstTick + tBURST_MIN)) {
// already interleaving, push next command to end of full burst
burst_gap = tBURST;
} else if (cmd_at < (rank_ref.lastBurstTick + tBURST)) {
// not at an interleave boundary after bandwidth check
// Shift command to tBURST boundary to avoid data contention
// Command will remain in the same burst window given that
// tBURST is less than tBURST_MAX
cmd_at = rank_ref.lastBurstTick + tBURST;
}
}
DPRINTF(DRAM, "Schedule RD/WR burst at tick %d\n", cmd_at);
// update the packet ready time
mem_pkt->readyTime = cmd_at + tCL + tBURST;
rank_ref.lastBurstTick = cmd_at;
// update the time for the next read/write burst for each
// bank (add a max with tCCD/tCCD_L/tCCD_L_WR here)
Tick dly_to_rd_cmd;
Tick dly_to_wr_cmd;
for (int j = 0; j < ranksPerChannel; j++) {
for (int i = 0; i < banksPerRank; i++) {
if (mem_pkt->rank == j) {
if (bankGroupArch &&
(bank_ref.bankgr == ranks[j]->banks[i].bankgr)) {
// bank group architecture requires longer delays between
// RD/WR burst commands to the same bank group.
// tCCD_L is default requirement for same BG timing
// tCCD_L_WR is required for write-to-write
// Need to also take bus turnaround delays into account
dly_to_rd_cmd = mem_pkt->isRead() ?
tCCD_L : std::max(tCCD_L, wrToRdDlySameBG);
dly_to_wr_cmd = mem_pkt->isRead() ?
std::max(tCCD_L, rdToWrDlySameBG) :
tCCD_L_WR;
} else {
// tBURST is default requirement for diff BG timing
// Need to also take bus turnaround delays into account
dly_to_rd_cmd = mem_pkt->isRead() ? burst_gap :
writeToReadDelay();
dly_to_wr_cmd = mem_pkt->isRead() ? readToWriteDelay() :
burst_gap;
}
} else {
// different rank is by default in a different bank group and
// doesn't require longer tCCD or additional RTW, WTR delays
// Need to account for rank-to-rank switching
dly_to_wr_cmd = rankToRankDelay();
dly_to_rd_cmd = rankToRankDelay();
}
ranks[j]->banks[i].rdAllowedAt = std::max(cmd_at + dly_to_rd_cmd,
ranks[j]->banks[i].rdAllowedAt);
ranks[j]->banks[i].wrAllowedAt = std::max(cmd_at + dly_to_wr_cmd,
ranks[j]->banks[i].wrAllowedAt);
}
}
// Save rank of current access
activeRank = mem_pkt->rank;
// If this is a write, we also need to respect the write recovery
// time before a precharge, in the case of a read, respect the
// read to precharge constraint
bank_ref.preAllowedAt = std::max(bank_ref.preAllowedAt,
mem_pkt->isRead() ? cmd_at + tRTP :
mem_pkt->readyTime + tWR);
// increment the bytes accessed and the accesses per row
bank_ref.bytesAccessed += burstSize;
++bank_ref.rowAccesses;
// if we reached the max, then issue with an auto-precharge
bool auto_precharge = pageMgmt == enums::close ||
bank_ref.rowAccesses == maxAccessesPerRow;
// if we did not hit the limit, we might still want to
// auto-precharge
if (!auto_precharge &&
(pageMgmt == enums::open_adaptive ||
pageMgmt == enums::close_adaptive)) {
// a twist on the open and close page policies:
// 1) open_adaptive page policy does not blindly keep the
// page open, but close it if there are no row hits, and there
// are bank conflicts in the queue
// 2) close_adaptive page policy does not blindly close the
// page, but closes it only if there are no row hits in the queue.
// In this case, only force an auto precharge when there
// are no same page hits in the queue
bool got_more_hits = false;
bool got_bank_conflict = false;
for (uint8_t i = 0; i < ctrl->numPriorities(); ++i) {
auto p = queue[i].begin();
// keep on looking until we find a hit or reach the end of the
// queue
// 1) if a hit is found, then both open and close adaptive
// policies keep the page open
// 2) if no hit is found, got_bank_conflict is set to true if a
// bank conflict request is waiting in the queue
// 3) make sure we are not considering the packet that we are
// currently dealing with
while (!got_more_hits && p != queue[i].end()) {
if (mem_pkt != (*p)) {
bool same_rank_bank = (mem_pkt->rank == (*p)->rank) &&
(mem_pkt->bank == (*p)->bank);
bool same_row = mem_pkt->row == (*p)->row;
got_more_hits |= same_rank_bank && same_row;
got_bank_conflict |= same_rank_bank && !same_row;
}
++p;
}
if (got_more_hits)
break;
}
// auto pre-charge when either
// 1) open_adaptive policy, we have not got any more hits, and
// have a bank conflict
// 2) close_adaptive policy and we have not got any more hits
auto_precharge = !got_more_hits &&
(got_bank_conflict || pageMgmt == enums::close_adaptive);
}
// DRAMPower trace command to be written
std::string mem_cmd = mem_pkt->isRead() ? "RD" : "WR";
// MemCommand required for DRAMPower library
MemCommand::cmds command = (mem_cmd == "RD") ? MemCommand::RD :
MemCommand::WR;
rank_ref.cmdList.push_back(Command(command, mem_pkt->bank, cmd_at));
DPRINTF(DRAMPower, "%llu,%s,%d,%d\n", divCeil(cmd_at, tCK) -
timeStampOffset, mem_cmd, mem_pkt->bank, mem_pkt->rank);
// if this access should use auto-precharge, then we are
// closing the row after the read/write burst
if (auto_precharge) {
// if auto-precharge push a PRE command at the correct tick to the
// list used by DRAMPower library to calculate power
prechargeBank(rank_ref, bank_ref, std::max(curTick(),
bank_ref.preAllowedAt), true);
DPRINTF(DRAM, "Auto-precharged bank: %d\n", mem_pkt->bankId);
}
// Update the stats and schedule the next request
if (mem_pkt->isRead()) {
// Every respQueue which will generate an event, increment count
++rank_ref.outstandingEvents;
stats.readBursts++;
if (row_hit)
stats.readRowHits++;
stats.bytesRead += burstSize;
stats.perBankRdBursts[mem_pkt->bankId]++;
// Update latency stats
stats.totMemAccLat += mem_pkt->readyTime - mem_pkt->entryTime;
stats.totQLat += cmd_at - mem_pkt->entryTime;
stats.totBusLat += tBURST;
} else {
// Schedule write done event to decrement event count
// after the readyTime has been reached
// Only schedule latest write event to minimize events
// required; only need to ensure that final event scheduled covers
// the time that writes are outstanding and bus is active
// to holdoff power-down entry events
if (!rank_ref.writeDoneEvent.scheduled()) {
schedule(rank_ref.writeDoneEvent, mem_pkt->readyTime);
// New event, increment count
++rank_ref.outstandingEvents;
} else if (rank_ref.writeDoneEvent.when() < mem_pkt->readyTime) {
reschedule(rank_ref.writeDoneEvent, mem_pkt->readyTime);
}
// will remove write from queue when returned to parent function
// decrement count for DRAM rank
--rank_ref.writeEntries;
stats.writeBursts++;
if (row_hit)
stats.writeRowHits++;
stats.bytesWritten += burstSize;
stats.perBankWrBursts[mem_pkt->bankId]++;
}
// Update bus state to reflect when previous command was issued
return std::make_pair(cmd_at, cmd_at + burst_gap);
}
void
DRAMInterface::addRankToRankDelay(Tick cmd_at)
{
// update timing for DRAM ranks due to bursts issued
// to ranks on other media interfaces
for (auto n : ranks) {
for (int i = 0; i < banksPerRank; i++) {
// different rank by default
// Need to only account for rank-to-rank switching
n->banks[i].rdAllowedAt = std::max(cmd_at + rankToRankDelay(),
n->banks[i].rdAllowedAt);
n->banks[i].wrAllowedAt = std::max(cmd_at + rankToRankDelay(),
n->banks[i].wrAllowedAt);
}
}
}
DRAMInterface::DRAMInterface(const DRAMInterfaceParams &_p)
: MemInterface(_p),
bankGroupsPerRank(_p.bank_groups_per_rank),
bankGroupArch(_p.bank_groups_per_rank > 0),
tCL(_p.tCL),
tBURST_MIN(_p.tBURST_MIN), tBURST_MAX(_p.tBURST_MAX),
tCCD_L_WR(_p.tCCD_L_WR), tCCD_L(_p.tCCD_L), tRCD(_p.tRCD),
tRP(_p.tRP), tRAS(_p.tRAS), tWR(_p.tWR), tRTP(_p.tRTP),
tRFC(_p.tRFC), tREFI(_p.tREFI), tRRD(_p.tRRD), tRRD_L(_p.tRRD_L),
tPPD(_p.tPPD), tAAD(_p.tAAD),
tXAW(_p.tXAW), tXP(_p.tXP), tXS(_p.tXS),
clkResyncDelay(tCL + _p.tBURST_MAX),
dataClockSync(_p.data_clock_sync),
burstInterleave(tBURST != tBURST_MIN),
twoCycleActivate(_p.two_cycle_activate),
activationLimit(_p.activation_limit),
wrToRdDlySameBG(tCL + _p.tBURST_MAX + _p.tWTR_L),
rdToWrDlySameBG(_p.tRTW + _p.tBURST_MAX),
pageMgmt(_p.page_policy),
maxAccessesPerRow(_p.max_accesses_per_row),
timeStampOffset(0), activeRank(0),
enableDRAMPowerdown(_p.enable_dram_powerdown),
lastStatsResetTick(0),
stats(*this)
{
DPRINTF(DRAM, "Setting up DRAM Interface\n");
fatal_if(!isPowerOf2(burstSize), "DRAM burst size %d is not allowed, "
"must be a power of two\n", burstSize);
// sanity check the ranks since we rely on bit slicing for the
// address decoding
fatal_if(!isPowerOf2(ranksPerChannel), "DRAM rank count of %d is "
"not allowed, must be a power of two\n", ranksPerChannel);
for (int i = 0; i < ranksPerChannel; i++) {
DPRINTF(DRAM, "Creating DRAM rank %d \n", i);
Rank* rank = new Rank(_p, i, *this);
ranks.push_back(rank);
}
// determine the dram actual capacity from the DRAM config in Mbytes
uint64_t deviceCapacity = deviceSize / (1024 * 1024) * devicesPerRank *
ranksPerChannel;
uint64_t capacity = 1ULL << ceilLog2(AbstractMemory::size());
DPRINTF(DRAM, "Memory capacity %lld (%lld) bytes\n", capacity,
AbstractMemory::size());
// if actual DRAM size does not match memory capacity in system warn!
if (deviceCapacity != capacity / (1024 * 1024))
warn("DRAM device capacity (%d Mbytes) does not match the "
"address range assigned (%d Mbytes)\n", deviceCapacity,
capacity / (1024 * 1024));
DPRINTF(DRAM, "Row buffer size %d bytes with %d bursts per row buffer\n",
rowBufferSize, burstsPerRowBuffer);
rowsPerBank = capacity / (rowBufferSize * banksPerRank * ranksPerChannel);
// some basic sanity checks
if (tREFI <= tRP || tREFI <= tRFC) {
fatal("tREFI (%d) must be larger than tRP (%d) and tRFC (%d)\n",
tREFI, tRP, tRFC);
}
// basic bank group architecture checks ->
if (bankGroupArch) {
// must have at least one bank per bank group
if (bankGroupsPerRank > banksPerRank) {
fatal("banks per rank (%d) must be equal to or larger than "
"banks groups per rank (%d)\n",
banksPerRank, bankGroupsPerRank);
}
// must have same number of banks in each bank group
if ((banksPerRank % bankGroupsPerRank) != 0) {
fatal("Banks per rank (%d) must be evenly divisible by bank "
"groups per rank (%d) for equal banks per bank group\n",
banksPerRank, bankGroupsPerRank);
}
// tCCD_L should be greater than minimal, back-to-back burst delay
if (tCCD_L <= tBURST) {
fatal("tCCD_L (%d) should be larger than the minimum bus delay "
"(%d) when bank groups per rank (%d) is greater than 1\n",
tCCD_L, tBURST, bankGroupsPerRank);
}
// tCCD_L_WR should be greater than minimal, back-to-back burst delay
if (tCCD_L_WR <= tBURST) {
fatal("tCCD_L_WR (%d) should be larger than the minimum bus delay "
" (%d) when bank groups per rank (%d) is greater than 1\n",
tCCD_L_WR, tBURST, bankGroupsPerRank);
}
// tRRD_L is greater than minimal, same bank group ACT-to-ACT delay
// some datasheets might specify it equal to tRRD
if (tRRD_L < tRRD) {
fatal("tRRD_L (%d) should be larger than tRRD (%d) when "
"bank groups per rank (%d) is greater than 1\n",
tRRD_L, tRRD, bankGroupsPerRank);
}
}
}
void
DRAMInterface::init()
{
AbstractMemory::init();
// a bit of sanity checks on the interleaving, save it for here to
// ensure that the system pointer is initialised
if (range.interleaved()) {
if (addrMapping == enums::RoRaBaChCo) {
if (rowBufferSize != range.granularity()) {
fatal("Channel interleaving of %s doesn't match RoRaBaChCo "
"address map\n", name());
}
} else if (addrMapping == enums::RoRaBaCoCh ||
addrMapping == enums::RoCoRaBaCh) {
// for the interleavings with channel bits in the bottom,
// if the system uses a channel striping granularity that
// is larger than the DRAM burst size, then map the
// sequential accesses within a stripe to a number of
// columns in the DRAM, effectively placing some of the
// lower-order column bits as the least-significant bits
// of the address (above the ones denoting the burst size)
assert(burstsPerStripe >= 1);
// channel striping has to be done at a granularity that
// is equal or larger to a cache line
if (system()->cacheLineSize() > range.granularity()) {
fatal("Channel interleaving of %s must be at least as large "
"as the cache line size\n", name());
}
// ...and equal or smaller than the row-buffer size
if (rowBufferSize < range.granularity()) {
fatal("Channel interleaving of %s must be at most as large "
"as the row-buffer size\n", name());
}
// this is essentially the check above, so just to be sure
assert(burstsPerStripe <= burstsPerRowBuffer);
}
}
}
void
DRAMInterface::startup()
{
if (system()->isTimingMode()) {
// timestamp offset should be in clock cycles for DRAMPower
timeStampOffset = divCeil(curTick(), tCK);
for (auto r : ranks) {
r->startup(curTick() + tREFI - tRP);
}
}
}
bool
DRAMInterface::isBusy()
{
int busy_ranks = 0;
for (auto r : ranks) {
if (!r->inRefIdleState()) {
if (r->pwrState != PWR_SREF) {
// rank is busy refreshing
DPRINTF(DRAMState, "Rank %d is not available\n", r->rank);
busy_ranks++;
// let the rank know that if it was waiting to drain, it
// is now done and ready to proceed
r->checkDrainDone();
}
// check if we were in self-refresh and haven't started
// to transition out
if ((r->pwrState == PWR_SREF) && r->inLowPowerState) {
DPRINTF(DRAMState, "Rank %d is in self-refresh\n", r->rank);
// if we have commands queued to this rank and we don't have
// a minimum number of active commands enqueued,
// exit self-refresh
if (r->forceSelfRefreshExit()) {
DPRINTF(DRAMState, "rank %d was in self refresh and"
" should wake up\n", r->rank);
//wake up from self-refresh
r->scheduleWakeUpEvent(tXS);
// things are brought back into action once a refresh is
// performed after self-refresh
// continue with selection for other ranks
}
}
}
}
return (busy_ranks == ranksPerChannel);
}
void DRAMInterface::setupRank(const uint8_t rank, const bool is_read)
{
// increment entry count of the rank based on packet type
if (is_read) {
++ranks[rank]->readEntries;
} else {
++ranks[rank]->writeEntries;
}
}
void
DRAMInterface::respondEvent(uint8_t rank)
{
Rank& rank_ref = *ranks[rank];
// if a read has reached its ready-time, decrement the number of reads
// At this point the packet has been handled and there is a possibility
// to switch to low-power mode if no other packet is available
--rank_ref.readEntries;
DPRINTF(DRAM, "number of read entries for rank %d is %d\n",
rank, rank_ref.readEntries);
// counter should at least indicate one outstanding request
// for this read
assert(rank_ref.outstandingEvents > 0);
// read response received, decrement count
--rank_ref.outstandingEvents;
// at this moment should not have transitioned to a low-power state
assert((rank_ref.pwrState != PWR_SREF) &&
(rank_ref.pwrState != PWR_PRE_PDN) &&
(rank_ref.pwrState != PWR_ACT_PDN));
// track if this is the last packet before idling
// and that there are no outstanding commands to this rank
if (rank_ref.isQueueEmpty() && rank_ref.outstandingEvents == 0 &&
rank_ref.inRefIdleState() && enableDRAMPowerdown) {
// verify that there are no events scheduled
assert(!rank_ref.activateEvent.scheduled());
assert(!rank_ref.prechargeEvent.scheduled());
// if coming from active state, schedule power event to
// active power-down else go to precharge power-down
DPRINTF(DRAMState, "Rank %d sleep at tick %d; current power state is "
"%d\n", rank, curTick(), rank_ref.pwrState);
// default to ACT power-down unless already in IDLE state
// could be in IDLE if PRE issued before data returned
PowerState next_pwr_state = PWR_ACT_PDN;
if (rank_ref.pwrState == PWR_IDLE) {
next_pwr_state = PWR_PRE_PDN;
}
rank_ref.powerDownSleep(next_pwr_state, curTick());
}
}
void
DRAMInterface::checkRefreshState(uint8_t rank)
{
Rank& rank_ref = *ranks[rank];
if ((rank_ref.refreshState == REF_PRE) &&
!rank_ref.prechargeEvent.scheduled()) {
// kick the refresh event loop into action again if banks already
// closed and just waiting for read to complete
schedule(rank_ref.refreshEvent, curTick());
}
}
void
DRAMInterface::drainRanks()
{
// also need to kick off events to exit self-refresh
for (auto r : ranks) {
// force self-refresh exit, which in turn will issue auto-refresh
if (r->pwrState == PWR_SREF) {
DPRINTF(DRAM,"Rank%d: Forcing self-refresh wakeup in drain\n",
r->rank);
r->scheduleWakeUpEvent(tXS);
}
}
}
bool
DRAMInterface::allRanksDrained() const
{
// true until proven false
bool all_ranks_drained = true;
for (auto r : ranks) {
// then verify that the power state is IDLE ensuring all banks are
// closed and rank is not in a low power state. Also verify that rank
// is idle from a refresh point of view.
all_ranks_drained = r->inPwrIdleState() && r->inRefIdleState() &&
all_ranks_drained;
}
return all_ranks_drained;
}
void
DRAMInterface::suspend()
{
for (auto r : ranks) {
r->suspend();
}
}
std::pair<std::vector<uint32_t>, bool>
DRAMInterface::minBankPrep(const MemPacketQueue& queue,
Tick min_col_at) const
{
Tick min_act_at = MaxTick;
std::vector<uint32_t> bank_mask(ranksPerChannel, 0);
// latest Tick for which ACT can occur without incurring additoinal
// delay on the data bus
const Tick hidden_act_max = std::max(min_col_at - tRCD, curTick());
// Flag condition when burst can issue back-to-back with previous burst
bool found_seamless_bank = false;
// Flag condition when bank can be opened without incurring additional
// delay on the data bus
bool hidden_bank_prep = false;
// determine if we have queued transactions targetting the
// bank in question
std::vector<bool> got_waiting(ranksPerChannel * banksPerRank, false);
for (const auto& p : queue) {
if (p->isDram() && ranks[p->rank]->inRefIdleState())
got_waiting[p->bankId] = true;
}
// Find command with optimal bank timing
// Will prioritize commands that can issue seamlessly.
for (int i = 0; i < ranksPerChannel; i++) {
for (int j = 0; j < banksPerRank; j++) {
uint16_t bank_id = i * banksPerRank + j;
// if we have waiting requests for the bank, and it is
// amongst the first available, update the mask
if (got_waiting[bank_id]) {
// make sure this rank is not currently refreshing.
assert(ranks[i]->inRefIdleState());
// simplistic approximation of when the bank can issue
// an activate, ignoring any rank-to-rank switching
// cost in this calculation
Tick act_at = ranks[i]->banks[j].openRow == Bank::NO_ROW ?
std::max(ranks[i]->banks[j].actAllowedAt, curTick()) :
std::max(ranks[i]->banks[j].preAllowedAt, curTick()) + tRP;
// When is the earliest the R/W burst can issue?
const Tick col_allowed_at = ctrl->inReadBusState(false) ?
ranks[i]->banks[j].rdAllowedAt :
ranks[i]->banks[j].wrAllowedAt;
Tick col_at = std::max(col_allowed_at, act_at + tRCD);
// bank can issue burst back-to-back (seamlessly) with
// previous burst
bool new_seamless_bank = col_at <= min_col_at;
// if we found a new seamless bank or we have no
// seamless banks, and got a bank with an earlier
// activate time, it should be added to the bit mask
if (new_seamless_bank ||
(!found_seamless_bank && act_at <= min_act_at)) {
// if we did not have a seamless bank before, and
// we do now, reset the bank mask, also reset it
// if we have not yet found a seamless bank and
// the activate time is smaller than what we have
// seen so far
if (!found_seamless_bank &&
(new_seamless_bank || act_at < min_act_at)) {
std::fill(bank_mask.begin(), bank_mask.end(), 0);
}
found_seamless_bank |= new_seamless_bank;
// ACT can occur 'behind the scenes'
hidden_bank_prep = act_at <= hidden_act_max;
// set the bit corresponding to the available bank
replaceBits(bank_mask[i], j, j, 1);
min_act_at = act_at;
}
}
}
}
return std::make_pair(bank_mask, hidden_bank_prep);
}
DRAMInterface::Rank::Rank(const DRAMInterfaceParams &_p,
int _rank, DRAMInterface& _dram)
: EventManager(&_dram), dram(_dram),
pwrStateTrans(PWR_IDLE), pwrStatePostRefresh(PWR_IDLE),
pwrStateTick(0), refreshDueAt(0), pwrState(PWR_IDLE),
refreshState(REF_IDLE), inLowPowerState(false), rank(_rank),
readEntries(0), writeEntries(0), outstandingEvents(0),
wakeUpAllowedAt(0), power(_p, false), banks(_p.banks_per_rank),
numBanksActive(0), actTicks(_p.activation_limit, 0), lastBurstTick(0),
writeDoneEvent([this]{ processWriteDoneEvent(); }, name()),
activateEvent([this]{ processActivateEvent(); }, name()),
prechargeEvent([this]{ processPrechargeEvent(); }, name()),
refreshEvent([this]{ processRefreshEvent(); }, name()),
powerEvent([this]{ processPowerEvent(); }, name()),
wakeUpEvent([this]{ processWakeUpEvent(); }, name()),
stats(_dram, *this)
{
for (int b = 0; b < _p.banks_per_rank; b++) {
banks[b].bank = b;
// GDDR addressing of banks to BG is linear.
// Here we assume that all DRAM generations address bank groups as
// follows:
if (_p.bank_groups_per_rank > 0) {
// Simply assign lower bits to bank group in order to
// rotate across bank groups as banks are incremented
// e.g. with 4 banks per bank group and 16 banks total:
// banks 0,4,8,12 are in bank group 0
// banks 1,5,9,13 are in bank group 1
// banks 2,6,10,14 are in bank group 2
// banks 3,7,11,15 are in bank group 3
banks[b].bankgr = b % _p.bank_groups_per_rank;
} else {
// No bank groups; simply assign to bank number
banks[b].bankgr = b;
}
}
}
void
DRAMInterface::Rank::startup(Tick ref_tick)
{
assert(ref_tick > curTick());
pwrStateTick = curTick();
// kick off the refresh, and give ourselves enough time to
// precharge
schedule(refreshEvent, ref_tick);
}
void
DRAMInterface::Rank::suspend()
{
deschedule(refreshEvent);
// Update the stats
updatePowerStats();
// don't automatically transition back to LP state after next REF
pwrStatePostRefresh = PWR_IDLE;
}
bool
DRAMInterface::Rank::isQueueEmpty() const
{
// check commmands in Q based on current bus direction
bool no_queued_cmds = (dram.ctrl->inReadBusState(true) &&
(readEntries == 0))
|| (dram.ctrl->inWriteBusState(true) &&
(writeEntries == 0));
return no_queued_cmds;
}
void
DRAMInterface::Rank::checkDrainDone()
{
// if this rank was waiting to drain it is now able to proceed to
// precharge
if (refreshState == REF_DRAIN) {
DPRINTF(DRAM, "Refresh drain done, now precharging\n");
refreshState = REF_PD_EXIT;
// hand control back to the refresh event loop
schedule(refreshEvent, curTick());
}
}
void
DRAMInterface::Rank::flushCmdList()
{
// at the moment sort the list of commands and update the counters
// for DRAMPower libray when doing a refresh
sort(cmdList.begin(), cmdList.end(), DRAMInterface::sortTime);
auto next_iter = cmdList.begin();
// push to commands to DRAMPower
for ( ; next_iter != cmdList.end() ; ++next_iter) {
Command cmd = *next_iter;
if (cmd.timeStamp <= curTick()) {
// Move all commands at or before curTick to DRAMPower
power.powerlib.doCommand(cmd.type, cmd.bank,
divCeil(cmd.timeStamp, dram.tCK) -
dram.timeStampOffset);
} else {
// done - found all commands at or before curTick()
// next_iter references the 1st command after curTick
break;
}
}
// reset cmdList to only contain commands after curTick
// if there are no commands after curTick, updated cmdList will be empty
// in this case, next_iter is cmdList.end()
cmdList.assign(next_iter, cmdList.end());
}
void
DRAMInterface::Rank::processActivateEvent()
{
// we should transition to the active state as soon as any bank is active
if (pwrState != PWR_ACT)
// note that at this point numBanksActive could be back at
// zero again due to a precharge scheduled in the future
schedulePowerEvent(PWR_ACT, curTick());
}
void
DRAMInterface::Rank::processPrechargeEvent()
{
// counter should at least indicate one outstanding request
// for this precharge
assert(outstandingEvents > 0);
// precharge complete, decrement count
--outstandingEvents;
// if we reached zero, then special conditions apply as we track
// if all banks are precharged for the power models
if (numBanksActive == 0) {
// no reads to this rank in the Q and no pending
// RD/WR or refresh commands
if (isQueueEmpty() && outstandingEvents == 0 &&
dram.enableDRAMPowerdown) {
// should still be in ACT state since bank still open
assert(pwrState == PWR_ACT);
// All banks closed - switch to precharge power down state.
DPRINTF(DRAMState, "Rank %d sleep at tick %d\n",
rank, curTick());
powerDownSleep(PWR_PRE_PDN, curTick());
} else {
// we should transition to the idle state when the last bank
// is precharged
schedulePowerEvent(PWR_IDLE, curTick());
}
}
}
void
DRAMInterface::Rank::processWriteDoneEvent()
{
// counter should at least indicate one outstanding request
// for this write
assert(outstandingEvents > 0);
// Write transfer on bus has completed
// decrement per rank counter
--outstandingEvents;
}
void
DRAMInterface::Rank::processRefreshEvent()
{
// when first preparing the refresh, remember when it was due
if ((refreshState == REF_IDLE) || (refreshState == REF_SREF_EXIT)) {
// remember when the refresh is due
refreshDueAt = curTick();
// proceed to drain
refreshState = REF_DRAIN;
// make nonzero while refresh is pending to ensure
// power down and self-refresh are not entered
++outstandingEvents;
DPRINTF(DRAM, "Refresh due\n");
}
// let any scheduled read or write to the same rank go ahead,
// after which it will
// hand control back to this event loop
if (refreshState == REF_DRAIN) {
// if a request is at the moment being handled and this request is
// accessing the current rank then wait for it to finish
if ((rank == dram.activeRank)
&& (dram.ctrl->requestEventScheduled())) {
// hand control over to the request loop until it is
// evaluated next
DPRINTF(DRAM, "Refresh awaiting draining\n");
return;
} else {
refreshState = REF_PD_EXIT;
}
}
// at this point, ensure that rank is not in a power-down state
if (refreshState == REF_PD_EXIT) {
// if rank was sleeping and we have't started exit process,
// wake-up for refresh
if (inLowPowerState) {
DPRINTF(DRAM, "Wake Up for refresh\n");
// save state and return after refresh completes
scheduleWakeUpEvent(dram.tXP);
return;
} else {
refreshState = REF_PRE;
}
}
// at this point, ensure that all banks are precharged
if (refreshState == REF_PRE) {
// precharge any active bank
if (numBanksActive != 0) {
// at the moment, we use a precharge all even if there is
// only a single bank open
DPRINTF(DRAM, "Precharging all\n");
// first determine when we can precharge
Tick pre_at = curTick();
for (auto &b : banks) {
// respect both causality and any existing bank
// constraints, some banks could already have a
// (auto) precharge scheduled
pre_at = std::max(b.preAllowedAt, pre_at);
}
// make sure all banks per rank are precharged, and for those that
// already are, update their availability
Tick act_allowed_at = pre_at + dram.tRP;
for (auto &b : banks) {
if (b.openRow != Bank::NO_ROW) {
dram.prechargeBank(*this, b, pre_at, true, false);
} else {
b.actAllowedAt = std::max(b.actAllowedAt, act_allowed_at);
b.preAllowedAt = std::max(b.preAllowedAt, pre_at);
}
}
// precharge all banks in rank
cmdList.push_back(Command(MemCommand::PREA, 0, pre_at));
DPRINTF(DRAMPower, "%llu,PREA,0,%d\n",
divCeil(pre_at, dram.tCK) -
dram.timeStampOffset, rank);
} else if ((pwrState == PWR_IDLE) && (outstandingEvents == 1)) {
// Banks are closed, have transitioned to IDLE state, and
// no outstanding ACT,RD/WR,Auto-PRE sequence scheduled
DPRINTF(DRAM, "All banks already precharged, starting refresh\n");
// go ahead and kick the power state machine into gear since
// we are already idle
schedulePowerEvent(PWR_REF, curTick());
} else {
// banks state is closed but haven't transitioned pwrState to IDLE
// or have outstanding ACT,RD/WR,Auto-PRE sequence scheduled
// should have outstanding precharge or read response event
assert(prechargeEvent.scheduled() ||
dram.ctrl->respondEventScheduled());
// will start refresh when pwrState transitions to IDLE
}
assert(numBanksActive == 0);
// wait for all banks to be precharged or read to complete
// When precharge commands are done, power state machine will
// transition to the idle state, and automatically move to a
// refresh, at that point it will also call this method to get
// the refresh event loop going again
// Similarly, when read response completes, if all banks are
// precharged, will call this method to get loop re-started
return;
}
// last but not least we perform the actual refresh
if (refreshState == REF_START) {
// should never get here with any banks active
assert(numBanksActive == 0);
assert(pwrState == PWR_REF);
Tick ref_done_at = curTick() + dram.tRFC;
for (auto &b : banks) {
b.actAllowedAt = ref_done_at;
}
// at the moment this affects all ranks
cmdList.push_back(Command(MemCommand::REF, 0, curTick()));
// Update the stats
updatePowerStats();
DPRINTF(DRAMPower, "%llu,REF,0,%d\n", divCeil(curTick(), dram.tCK) -
dram.timeStampOffset, rank);
// Update for next refresh
refreshDueAt += dram.tREFI;
// make sure we did not wait so long that we cannot make up
// for it
if (refreshDueAt < ref_done_at) {
fatal("Refresh was delayed so long we cannot catch up\n");
}
// Run the refresh and schedule event to transition power states
// when refresh completes
refreshState = REF_RUN;
schedule(refreshEvent, ref_done_at);
return;
}
if (refreshState == REF_RUN) {
// should never get here with any banks active
assert(numBanksActive == 0);
assert(pwrState == PWR_REF);
assert(!powerEvent.scheduled());
if ((dram.ctrl->drainState() == DrainState::Draining) ||
(dram.ctrl->drainState() == DrainState::Drained)) {
// if draining, do not re-enter low-power mode.
// simply go to IDLE and wait
schedulePowerEvent(PWR_IDLE, curTick());
} else {
// At the moment, we sleep when the refresh ends and wait to be
// woken up again if previously in a low-power state.
if (pwrStatePostRefresh != PWR_IDLE) {
// power State should be power Refresh
assert(pwrState == PWR_REF);
DPRINTF(DRAMState, "Rank %d sleeping after refresh and was in "
"power state %d before refreshing\n", rank,
pwrStatePostRefresh);
powerDownSleep(pwrState, curTick());
// Force PRE power-down if there are no outstanding commands
// in Q after refresh.
} else if (isQueueEmpty() && dram.enableDRAMPowerdown) {
// still have refresh event outstanding but there should
// be no other events outstanding
assert(outstandingEvents == 1);
DPRINTF(DRAMState, "Rank %d sleeping after refresh but was NOT"
" in a low power state before refreshing\n", rank);
powerDownSleep(PWR_PRE_PDN, curTick());
} else {
// move to the idle power state once the refresh is done, this
// will also move the refresh state machine to the refresh
// idle state
schedulePowerEvent(PWR_IDLE, curTick());
}
}
// At this point, we have completed the current refresh.
// In the SREF bypass case, we do not get to this state in the
// refresh STM and therefore can always schedule next event.
// Compensate for the delay in actually performing the refresh
// when scheduling the next one
schedule(refreshEvent, refreshDueAt - dram.tRP);
DPRINTF(DRAMState, "Refresh done at %llu and next refresh"
" at %llu\n", curTick(), refreshDueAt);
}
}
void
DRAMInterface::Rank::schedulePowerEvent(PowerState pwr_state, Tick tick)
{
// respect causality
assert(tick >= curTick());
if (!powerEvent.scheduled()) {
DPRINTF(DRAMState, "Scheduling power event at %llu to state %d\n",
tick, pwr_state);
// insert the new transition
pwrStateTrans = pwr_state;
schedule(powerEvent, tick);
} else {
panic("Scheduled power event at %llu to state %d, "
"with scheduled event at %llu to %d\n", tick, pwr_state,
powerEvent.when(), pwrStateTrans);
}
}
void
DRAMInterface::Rank::powerDownSleep(PowerState pwr_state, Tick tick)
{
// if low power state is active low, schedule to active low power state.
// in reality tCKE is needed to enter active low power. This is neglected
// here and could be added in the future.
if (pwr_state == PWR_ACT_PDN) {
schedulePowerEvent(pwr_state, tick);
// push command to DRAMPower
cmdList.push_back(Command(MemCommand::PDN_F_ACT, 0, tick));
DPRINTF(DRAMPower, "%llu,PDN_F_ACT,0,%d\n", divCeil(tick,
dram.tCK) - dram.timeStampOffset, rank);
} else if (pwr_state == PWR_PRE_PDN) {
// if low power state is precharge low, schedule to precharge low
// power state. In reality tCKE is needed to enter active low power.
// This is neglected here.
schedulePowerEvent(pwr_state, tick);
//push Command to DRAMPower
cmdList.push_back(Command(MemCommand::PDN_F_PRE, 0, tick));
DPRINTF(DRAMPower, "%llu,PDN_F_PRE,0,%d\n", divCeil(tick,
dram.tCK) - dram.timeStampOffset, rank);
} else if (pwr_state == PWR_REF) {
// if a refresh just occurred
// transition to PRE_PDN now that all banks are closed
// precharge power down requires tCKE to enter. For simplicity
// this is not considered.
schedulePowerEvent(PWR_PRE_PDN, tick);
//push Command to DRAMPower
cmdList.push_back(Command(MemCommand::PDN_F_PRE, 0, tick));
DPRINTF(DRAMPower, "%llu,PDN_F_PRE,0,%d\n", divCeil(tick,
dram.tCK) - dram.timeStampOffset, rank);
} else if (pwr_state == PWR_SREF) {
// should only enter SREF after PRE-PD wakeup to do a refresh
assert(pwrStatePostRefresh == PWR_PRE_PDN);
// self refresh requires time tCKESR to enter. For simplicity,
// this is not considered.
schedulePowerEvent(PWR_SREF, tick);
// push Command to DRAMPower
cmdList.push_back(Command(MemCommand::SREN, 0, tick));
DPRINTF(DRAMPower, "%llu,SREN,0,%d\n", divCeil(tick,
dram.tCK) - dram.timeStampOffset, rank);
}
// Ensure that we don't power-down and back up in same tick
// Once we commit to PD entry, do it and wait for at least 1tCK
// This could be replaced with tCKE if/when that is added to the model
wakeUpAllowedAt = tick + dram.tCK;
// Transitioning to a low power state, set flag
inLowPowerState = true;
}
void
DRAMInterface::Rank::scheduleWakeUpEvent(Tick exit_delay)
{
Tick wake_up_tick = std::max(curTick(), wakeUpAllowedAt);
DPRINTF(DRAMState, "Scheduling wake-up for rank %d at tick %d\n",
rank, wake_up_tick);
// if waking for refresh, hold previous state
// else reset state back to IDLE
if (refreshState == REF_PD_EXIT) {
pwrStatePostRefresh = pwrState;
} else {
// don't automatically transition back to LP state after next REF
pwrStatePostRefresh = PWR_IDLE;
}
// schedule wake-up with event to ensure entry has completed before
// we try to wake-up
schedule(wakeUpEvent, wake_up_tick);
for (auto &b : banks) {
// respect both causality and any existing bank
// constraints, some banks could already have a
// (auto) precharge scheduled
b.wrAllowedAt = std::max(wake_up_tick + exit_delay, b.wrAllowedAt);
b.rdAllowedAt = std::max(wake_up_tick + exit_delay, b.rdAllowedAt);
b.preAllowedAt = std::max(wake_up_tick + exit_delay, b.preAllowedAt);
b.actAllowedAt = std::max(wake_up_tick + exit_delay, b.actAllowedAt);
}
// Transitioning out of low power state, clear flag
inLowPowerState = false;
// push to DRAMPower
// use pwrStateTrans for cases where we have a power event scheduled
// to enter low power that has not yet been processed
if (pwrStateTrans == PWR_ACT_PDN) {
cmdList.push_back(Command(MemCommand::PUP_ACT, 0, wake_up_tick));
DPRINTF(DRAMPower, "%llu,PUP_ACT,0,%d\n", divCeil(wake_up_tick,
dram.tCK) - dram.timeStampOffset, rank);
} else if (pwrStateTrans == PWR_PRE_PDN) {
cmdList.push_back(Command(MemCommand::PUP_PRE, 0, wake_up_tick));
DPRINTF(DRAMPower, "%llu,PUP_PRE,0,%d\n", divCeil(wake_up_tick,
dram.tCK) - dram.timeStampOffset, rank);
} else if (pwrStateTrans == PWR_SREF) {
cmdList.push_back(Command(MemCommand::SREX, 0, wake_up_tick));
DPRINTF(DRAMPower, "%llu,SREX,0,%d\n", divCeil(wake_up_tick,
dram.tCK) - dram.timeStampOffset, rank);
}
}
void
DRAMInterface::Rank::processWakeUpEvent()
{
// Should be in a power-down or self-refresh state
assert((pwrState == PWR_ACT_PDN) || (pwrState == PWR_PRE_PDN) ||
(pwrState == PWR_SREF));
// Check current state to determine transition state
if (pwrState == PWR_ACT_PDN) {
// banks still open, transition to PWR_ACT
schedulePowerEvent(PWR_ACT, curTick());
} else {
// transitioning from a precharge power-down or self-refresh state
// banks are closed - transition to PWR_IDLE
schedulePowerEvent(PWR_IDLE, curTick());
}
}
void
DRAMInterface::Rank::processPowerEvent()
{
assert(curTick() >= pwrStateTick);
// remember where we were, and for how long
Tick duration = curTick() - pwrStateTick;
PowerState prev_state = pwrState;
// update the accounting
stats.pwrStateTime[prev_state] += duration;
// track to total idle time
if ((prev_state == PWR_PRE_PDN) || (prev_state == PWR_ACT_PDN) ||
(prev_state == PWR_SREF)) {
stats.totalIdleTime += duration;
}
pwrState = pwrStateTrans;
pwrStateTick = curTick();
// if rank was refreshing, make sure to start scheduling requests again
if (prev_state == PWR_REF) {
// bus IDLED prior to REF
// counter should be one for refresh command only
assert(outstandingEvents == 1);
// REF complete, decrement count and go back to IDLE
--outstandingEvents;
refreshState = REF_IDLE;
DPRINTF(DRAMState, "Was refreshing for %llu ticks\n", duration);
// if moving back to power-down after refresh
if (pwrState != PWR_IDLE) {
assert(pwrState == PWR_PRE_PDN);
DPRINTF(DRAMState, "Switching to power down state after refreshing"
" rank %d at %llu tick\n", rank, curTick());
}
// completed refresh event, ensure next request is scheduled
if (!dram.ctrl->requestEventScheduled()) {
DPRINTF(DRAM, "Scheduling next request after refreshing"
" rank %d\n", rank);
dram.ctrl->restartScheduler(curTick());
}
}
if ((pwrState == PWR_ACT) && (refreshState == REF_PD_EXIT)) {
// have exited ACT PD
assert(prev_state == PWR_ACT_PDN);
// go back to REF event and close banks
refreshState = REF_PRE;
schedule(refreshEvent, curTick());
} else if (pwrState == PWR_IDLE) {
DPRINTF(DRAMState, "All banks precharged\n");
if (prev_state == PWR_SREF) {
// set refresh state to REF_SREF_EXIT, ensuring inRefIdleState
// continues to return false during tXS after SREF exit
// Schedule a refresh which kicks things back into action
// when it finishes
refreshState = REF_SREF_EXIT;
schedule(refreshEvent, curTick() + dram.tXS);
} else {
// if we have a pending refresh, and are now moving to
// the idle state, directly transition to, or schedule refresh
if ((refreshState == REF_PRE) || (refreshState == REF_PD_EXIT)) {
// ensure refresh is restarted only after final PRE command.
// do not restart refresh if controller is in an intermediate
// state, after PRE_PDN exit, when banks are IDLE but an
// ACT is scheduled.
if (!activateEvent.scheduled()) {
// there should be nothing waiting at this point
assert(!powerEvent.scheduled());
if (refreshState == REF_PD_EXIT) {
// exiting PRE PD, will be in IDLE until tXP expires
// and then should transition to PWR_REF state
assert(prev_state == PWR_PRE_PDN);
schedulePowerEvent(PWR_REF, curTick() + dram.tXP);
} else if (refreshState == REF_PRE) {
// can directly move to PWR_REF state and proceed below
pwrState = PWR_REF;
}
} else {
// must have PRE scheduled to transition back to IDLE
// and re-kick off refresh
assert(prechargeEvent.scheduled());
}
}
}
}
// transition to the refresh state and re-start refresh process
// refresh state machine will schedule the next power state transition
if (pwrState == PWR_REF) {
// completed final PRE for refresh or exiting power-down
assert(refreshState == REF_PRE || refreshState == REF_PD_EXIT);
// exited PRE PD for refresh, with no pending commands
// bypass auto-refresh and go straight to SREF, where memory
// will issue refresh immediately upon entry
if (pwrStatePostRefresh == PWR_PRE_PDN && isQueueEmpty() &&
(dram.ctrl->drainState() != DrainState::Draining) &&
(dram.ctrl->drainState() != DrainState::Drained) &&
dram.enableDRAMPowerdown) {
DPRINTF(DRAMState, "Rank %d bypassing refresh and transitioning "
"to self refresh at %11u tick\n", rank, curTick());
powerDownSleep(PWR_SREF, curTick());
// Since refresh was bypassed, remove event by decrementing count
assert(outstandingEvents == 1);
--outstandingEvents;
// reset state back to IDLE temporarily until SREF is entered
pwrState = PWR_IDLE;
// Not bypassing refresh for SREF entry
} else {
DPRINTF(DRAMState, "Refreshing\n");
// there should be nothing waiting at this point
assert(!powerEvent.scheduled());
// kick the refresh event loop into action again, and that
// in turn will schedule a transition to the idle power
// state once the refresh is done
schedule(refreshEvent, curTick());
// Banks transitioned to IDLE, start REF
refreshState = REF_START;
}
}
}
void
DRAMInterface::Rank::updatePowerStats()
{
// All commands up to refresh have completed
// flush cmdList to DRAMPower
flushCmdList();
// Call the function that calculates window energy at intermediate update
// events like at refresh, stats dump as well as at simulation exit.
// Window starts at the last time the calcWindowEnergy function was called
// and is upto current time.
power.powerlib.calcWindowEnergy(divCeil(curTick(), dram.tCK) -
dram.timeStampOffset);
// Get the energy from DRAMPower
Data::MemoryPowerModel::Energy energy = power.powerlib.getEnergy();
// The energy components inside the power lib are calculated over
// the window so accumulate into the corresponding gem5 stat
stats.actEnergy += energy.act_energy * dram.devicesPerRank;
stats.preEnergy += energy.pre_energy * dram.devicesPerRank;
stats.readEnergy += energy.read_energy * dram.devicesPerRank;
stats.writeEnergy += energy.write_energy * dram.devicesPerRank;
stats.refreshEnergy += energy.ref_energy * dram.devicesPerRank;
stats.actBackEnergy += energy.act_stdby_energy * dram.devicesPerRank;
stats.preBackEnergy += energy.pre_stdby_energy * dram.devicesPerRank;
stats.actPowerDownEnergy += energy.f_act_pd_energy * dram.devicesPerRank;
stats.prePowerDownEnergy += energy.f_pre_pd_energy * dram.devicesPerRank;
stats.selfRefreshEnergy += energy.sref_energy * dram.devicesPerRank;
// Accumulate window energy into the total energy.
stats.totalEnergy += energy.window_energy * dram.devicesPerRank;
// Average power must not be accumulated but calculated over the time
// since last stats reset. sim_clock::Frequency is tick period not tick
// frequency.
// energy (pJ) 1e-9
// power (mW) = ----------- * ----------
// time (tick) tick_frequency
stats.averagePower = (stats.totalEnergy.value() /
(curTick() - dram.lastStatsResetTick)) *
(sim_clock::Frequency / 1000000000.0);
}
void
DRAMInterface::Rank::computeStats()
{
DPRINTF(DRAM,"Computing stats due to a dump callback\n");
// Update the stats
updatePowerStats();
// final update of power state times
stats.pwrStateTime[pwrState] += (curTick() - pwrStateTick);
pwrStateTick = curTick();
}
void
DRAMInterface::Rank::resetStats() {
// The only way to clear the counters in DRAMPower is to call
// calcWindowEnergy function as that then calls clearCounters. The
// clearCounters method itself is private.
power.powerlib.calcWindowEnergy(divCeil(curTick(), dram.tCK) -
dram.timeStampOffset);
}
bool
DRAMInterface::Rank::forceSelfRefreshExit() const {
return (readEntries != 0) ||
(dram.ctrl->inWriteBusState(true) && (writeEntries != 0));
}
void
DRAMInterface::DRAMStats::resetStats()
{
dram.lastStatsResetTick = curTick();
}
DRAMInterface::DRAMStats::DRAMStats(DRAMInterface &_dram)
: statistics::Group(&_dram),
dram(_dram),
ADD_STAT(readBursts, statistics::units::Count::get(),
"Number of DRAM read bursts"),
ADD_STAT(writeBursts, statistics::units::Count::get(),
"Number of DRAM write bursts"),
ADD_STAT(perBankRdBursts, statistics::units::Count::get(),
"Per bank write bursts"),
ADD_STAT(perBankWrBursts, statistics::units::Count::get(),
"Per bank write bursts"),
ADD_STAT(totQLat, statistics::units::Tick::get(), "Total ticks spent queuing"),
ADD_STAT(totBusLat, statistics::units::Tick::get(),
"Total ticks spent in databus transfers"),
ADD_STAT(totMemAccLat, statistics::units::Tick::get(),
"Total ticks spent from burst creation until serviced "
"by the DRAM"),
ADD_STAT(avgQLat, statistics::units::Rate<
statistics::units::Tick, statistics::units::Count>::get(),
"Average queueing delay per DRAM burst"),
ADD_STAT(avgBusLat, statistics::units::Rate<
statistics::units::Tick, statistics::units::Count>::get(),
"Average bus latency per DRAM burst"),
ADD_STAT(avgMemAccLat, statistics::units::Rate<
statistics::units::Tick, statistics::units::Count>::get(),
"Average memory access latency per DRAM burst"),
ADD_STAT(readRowHits, statistics::units::Count::get(),
"Number of row buffer hits during reads"),
ADD_STAT(writeRowHits, statistics::units::Count::get(),
"Number of row buffer hits during writes"),
ADD_STAT(readRowHitRate, statistics::units::Ratio::get(),
"Row buffer hit rate for reads"),
ADD_STAT(writeRowHitRate, statistics::units::Ratio::get(),
"Row buffer hit rate for writes"),
ADD_STAT(bytesPerActivate, statistics::units::Byte::get(),
"Bytes accessed per row activation"),
ADD_STAT(bytesRead, statistics::units::Byte::get(),
"Total bytes read"),
ADD_STAT(bytesWritten, statistics::units::Byte::get(),
"Total bytes written"),
ADD_STAT(avgRdBW, statistics::units::Rate<
statistics::units::Byte, statistics::units::Second>::get(),
"Average DRAM read bandwidth in MiBytes/s"),
ADD_STAT(avgWrBW, statistics::units::Rate<
statistics::units::Byte, statistics::units::Second>::get(),
"Average DRAM write bandwidth in MiBytes/s"),
ADD_STAT(peakBW, statistics::units::Rate<
statistics::units::Byte, statistics::units::Second>::get(),
"Theoretical peak bandwidth in MiByte/s"),
ADD_STAT(busUtil, statistics::units::Ratio::get(),
"Data bus utilization in percentage"),
ADD_STAT(busUtilRead, statistics::units::Ratio::get(),
"Data bus utilization in percentage for reads"),
ADD_STAT(busUtilWrite, statistics::units::Ratio::get(),
"Data bus utilization in percentage for writes"),
ADD_STAT(pageHitRate, statistics::units::Ratio::get(),
"Row buffer hit rate, read and write combined")
{
}
void
DRAMInterface::DRAMStats::regStats()
{
using namespace statistics;
avgQLat.precision(2);
avgBusLat.precision(2);
avgMemAccLat.precision(2);
readRowHitRate.precision(2);
writeRowHitRate.precision(2);
perBankRdBursts.init(dram.banksPerRank * dram.ranksPerChannel);
perBankWrBursts.init(dram.banksPerRank * dram.ranksPerChannel);
bytesPerActivate
.init(dram.maxAccessesPerRow ?
dram.maxAccessesPerRow : dram.rowBufferSize)
.flags(nozero);
peakBW.precision(2);
busUtil.precision(2);
busUtilWrite.precision(2);
busUtilRead.precision(2);
pageHitRate.precision(2);
// Formula stats
avgQLat = totQLat / readBursts;
avgBusLat = totBusLat / readBursts;
avgMemAccLat = totMemAccLat / readBursts;
readRowHitRate = (readRowHits / readBursts) * 100;
writeRowHitRate = (writeRowHits / writeBursts) * 100;
avgRdBW = (bytesRead / 1000000) / simSeconds;
avgWrBW = (bytesWritten / 1000000) / simSeconds;
peakBW = (sim_clock::Frequency / dram.burstDelay()) *
dram.bytesPerBurst() / 1000000;
busUtil = (avgRdBW + avgWrBW) / peakBW * 100;
busUtilRead = avgRdBW / peakBW * 100;
busUtilWrite = avgWrBW / peakBW * 100;
pageHitRate = (writeRowHits + readRowHits) /
(writeBursts + readBursts) * 100;
}
DRAMInterface::RankStats::RankStats(DRAMInterface &_dram, Rank &_rank)
: statistics::Group(&_dram, csprintf("rank%d", _rank.rank).c_str()),
rank(_rank),
ADD_STAT(actEnergy, statistics::units::Joule::get(),
"Energy for activate commands per rank (pJ)"),
ADD_STAT(preEnergy, statistics::units::Joule::get(),
"Energy for precharge commands per rank (pJ)"),
ADD_STAT(readEnergy, statistics::units::Joule::get(),
"Energy for read commands per rank (pJ)"),
ADD_STAT(writeEnergy, statistics::units::Joule::get(),
"Energy for write commands per rank (pJ)"),
ADD_STAT(refreshEnergy, statistics::units::Joule::get(),
"Energy for refresh commands per rank (pJ)"),
ADD_STAT(actBackEnergy, statistics::units::Joule::get(),
"Energy for active background per rank (pJ)"),
ADD_STAT(preBackEnergy, statistics::units::Joule::get(),
"Energy for precharge background per rank (pJ)"),
ADD_STAT(actPowerDownEnergy, statistics::units::Joule::get(),
"Energy for active power-down per rank (pJ)"),
ADD_STAT(prePowerDownEnergy, statistics::units::Joule::get(),
"Energy for precharge power-down per rank (pJ)"),
ADD_STAT(selfRefreshEnergy, statistics::units::Joule::get(),
"Energy for self refresh per rank (pJ)"),
ADD_STAT(totalEnergy, statistics::units::Joule::get(),
"Total energy per rank (pJ)"),
ADD_STAT(averagePower, statistics::units::Watt::get(),
"Core power per rank (mW)"),
ADD_STAT(totalIdleTime, statistics::units::Tick::get(),
"Total Idle time Per DRAM Rank"),
ADD_STAT(pwrStateTime, statistics::units::Tick::get(),
"Time in different power states")
{
}
void
DRAMInterface::RankStats::regStats()
{
statistics::Group::regStats();
pwrStateTime
.init(6)
.subname(0, "IDLE")
.subname(1, "REF")
.subname(2, "SREF")
.subname(3, "PRE_PDN")
.subname(4, "ACT")
.subname(5, "ACT_PDN");
}
void
DRAMInterface::RankStats::resetStats()
{
statistics::Group::resetStats();
rank.resetStats();
}
void
DRAMInterface::RankStats::preDumpStats()
{
statistics::Group::preDumpStats();
rank.computeStats();
}
NVMInterface::NVMInterface(const NVMInterfaceParams &_p)
: MemInterface(_p),
maxPendingWrites(_p.max_pending_writes),
maxPendingReads(_p.max_pending_reads),
twoCycleRdWr(_p.two_cycle_rdwr),
tREAD(_p.tREAD), tWRITE(_p.tWRITE), tSEND(_p.tSEND),
stats(*this),
writeRespondEvent([this]{ processWriteRespondEvent(); }, name()),
readReadyEvent([this]{ processReadReadyEvent(); }, name()),
nextReadAt(0), numPendingReads(0), numReadDataReady(0),
numReadsToIssue(0), numWritesQueued(0)
{
DPRINTF(NVM, "Setting up NVM Interface\n");
fatal_if(!isPowerOf2(burstSize), "NVM burst size %d is not allowed, "
"must be a power of two\n", burstSize);
// sanity check the ranks since we rely on bit slicing for the
// address decoding
fatal_if(!isPowerOf2(ranksPerChannel), "NVM rank count of %d is "
"not allowed, must be a power of two\n", ranksPerChannel);
for (int i =0; i < ranksPerChannel; i++) {
// Add NVM ranks to the system
DPRINTF(NVM, "Creating NVM rank %d \n", i);
Rank* rank = new Rank(_p, i, *this);
ranks.push_back(rank);
}
uint64_t capacity = 1ULL << ceilLog2(AbstractMemory::size());
DPRINTF(NVM, "NVM capacity %lld (%lld) bytes\n", capacity,
AbstractMemory::size());
rowsPerBank = capacity / (rowBufferSize *
banksPerRank * ranksPerChannel);
}
NVMInterface::Rank::Rank(const NVMInterfaceParams &_p,
int _rank, NVMInterface& _nvm)
: EventManager(&_nvm), rank(_rank), banks(_p.banks_per_rank)
{
for (int b = 0; b < _p.banks_per_rank; b++) {
banks[b].bank = b;
// No bank groups; simply assign to bank number
banks[b].bankgr = b;
}
}
void
NVMInterface::init()
{
AbstractMemory::init();
}
void NVMInterface::setupRank(const uint8_t rank, const bool is_read)
{
if (is_read) {
// increment count to trigger read and track number of reads in Q
numReadsToIssue++;
} else {
// increment count to track number of writes in Q
numWritesQueued++;
}
}
std::pair<MemPacketQueue::iterator, Tick>
NVMInterface::chooseNextFRFCFS(MemPacketQueue& queue, Tick min_col_at) const
{
// remember if we found a hit, but one that cannit issue seamlessly
bool found_prepped_pkt = false;
auto selected_pkt_it = queue.end();
Tick selected_col_at = MaxTick;
for (auto i = queue.begin(); i != queue.end() ; ++i) {
MemPacket* pkt = *i;
// select optimal NVM packet in Q
if (!pkt->isDram()) {
const Bank& bank = ranks[pkt->rank]->banks[pkt->bank];
const Tick col_allowed_at = pkt->isRead() ? bank.rdAllowedAt :
bank.wrAllowedAt;
// check if rank is not doing a refresh and thus is available,
// if not, jump to the next packet
if (burstReady(pkt)) {
DPRINTF(NVM, "%s bank %d - Rank %d available\n", __func__,
pkt->bank, pkt->rank);
// no additional rank-to-rank or media delays
if (col_allowed_at <= min_col_at) {
// FCFS within entries that can issue without
// additional delay, such as same rank accesses
// or media delay requirements
selected_pkt_it = i;
selected_col_at = col_allowed_at;
// no need to look through the remaining queue entries
DPRINTF(NVM, "%s Seamless buffer hit\n", __func__);
break;
} else if (!found_prepped_pkt) {
// packet is to prepped region but cannnot issue
// seamlessly; remember this one and continue
selected_pkt_it = i;
selected_col_at = col_allowed_at;
DPRINTF(NVM, "%s Prepped packet found \n", __func__);
found_prepped_pkt = true;
}
} else {
DPRINTF(NVM, "%s bank %d - Rank %d not available\n", __func__,
pkt->bank, pkt->rank);
}
}
}
if (selected_pkt_it == queue.end()) {
DPRINTF(NVM, "%s no available NVM ranks found\n", __func__);
}
return std::make_pair(selected_pkt_it, selected_col_at);
}
void
NVMInterface::chooseRead(MemPacketQueue& queue)
{
Tick cmd_at = std::max(curTick(), nextReadAt);
// This method does the arbitration between non-deterministic read
// requests to NVM. The chosen packet is not removed from the queue
// at this time. Removal from the queue will occur when the data is
// ready and a separate SEND command is issued to retrieve it via the
// chooseNext function in the top-level controller.
assert(!queue.empty());
assert(numReadsToIssue > 0);
numReadsToIssue--;
// For simplicity, issue non-deterministic reads in order (fcfs)
for (auto i = queue.begin(); i != queue.end() ; ++i) {
MemPacket* pkt = *i;
// Find 1st NVM read packet that hasn't issued read command
if (pkt->readyTime == MaxTick && !pkt->isDram() && pkt->isRead()) {
// get the bank
Bank& bank_ref = ranks[pkt->rank]->banks[pkt->bank];
// issueing a read, inc counter and verify we haven't overrun
numPendingReads++;
assert(numPendingReads <= maxPendingReads);
// increment the bytes accessed and the accesses per row
bank_ref.bytesAccessed += burstSize;
// Verify command bandiwth to issue
// Host can issue read immediately uith buffering closer
// to the NVM. The actual execution at the NVM may be delayed
// due to busy resources
if (twoCycleRdWr) {
cmd_at = ctrl->verifyMultiCmd(cmd_at,
maxCommandsPerWindow, tCK);
} else {
cmd_at = ctrl->verifySingleCmd(cmd_at,
maxCommandsPerWindow);
}
// Update delay to next read
// Ensures single read command issued per cycle
nextReadAt = cmd_at + tCK;
// If accessing a new location in this bank, update timing
// and stats
if (bank_ref.openRow != pkt->row) {
// update the open bank, re-using row field
bank_ref.openRow = pkt->row;
// sample the bytes accessed to a buffer in this bank
// here when we are re-buffering the data
stats.bytesPerBank.sample(bank_ref.bytesAccessed);
// start counting anew
bank_ref.bytesAccessed = 0;
// holdoff next command to this bank until the read completes
// and the data has been successfully buffered
// can pipeline accesses to the same bank, sending them
// across the interface B2B, but will incur full access
// delay between data ready responses to different buffers
// in a bank
bank_ref.actAllowedAt = std::max(cmd_at,
bank_ref.actAllowedAt) + tREAD;
}
// update per packet readyTime to holdoff burst read operation
// overloading readyTime, which will be updated again when the
// burst is issued
pkt->readyTime = std::max(cmd_at, bank_ref.actAllowedAt);
DPRINTF(NVM, "Issuing NVM Read to bank %d at tick %d. "
"Data ready at %d\n",
bank_ref.bank, cmd_at, pkt->readyTime);
// Insert into read ready queue. It will be handled after
// the media delay has been met
if (readReadyQueue.empty()) {
assert(!readReadyEvent.scheduled());
schedule(readReadyEvent, pkt->readyTime);
} else if (readReadyEvent.when() > pkt->readyTime) {
// move it sooner in time, to the first read with data
reschedule(readReadyEvent, pkt->readyTime);
} else {
assert(readReadyEvent.scheduled());
}
readReadyQueue.push_back(pkt->readyTime);
// found an NVM read to issue - break out
break;
}
}
}
void
NVMInterface::processReadReadyEvent()
{
// signal that there is read data ready to be transmitted
numReadDataReady++;
DPRINTF(NVM,
"processReadReadyEvent(): Data for an NVM read is ready. "
"numReadDataReady is %d\t numPendingReads is %d\n",
numReadDataReady, numPendingReads);
// Find lowest ready time and verify it is equal to curTick
// also find the next lowest to schedule next event
// Done with this response, erase entry
auto ready_it = readReadyQueue.begin();
Tick next_ready_at = MaxTick;
for (auto i = readReadyQueue.begin(); i != readReadyQueue.end() ; ++i) {
if (*ready_it > *i) {
next_ready_at = *ready_it;
ready_it = i;
} else if ((next_ready_at > *i) && (i != ready_it)) {
next_ready_at = *i;
}
}
// Verify we found the time of this event and remove it
assert(*ready_it == curTick());
readReadyQueue.erase(ready_it);
if (!readReadyQueue.empty()) {
assert(readReadyQueue.front() >= curTick());
assert(!readReadyEvent.scheduled());
schedule(readReadyEvent, next_ready_at);
}
// It is possible that a new command kicks things back into
// action before reaching this point but need to ensure that we
// continue to process new commands as read data becomes ready
// This will also trigger a drain if needed
if (!ctrl->requestEventScheduled()) {
DPRINTF(NVM, "Restart controller scheduler immediately\n");
ctrl->restartScheduler(curTick());
}
}
bool
NVMInterface::burstReady(MemPacket* pkt) const {
bool read_rdy = pkt->isRead() && (ctrl->inReadBusState(true)) &&
(pkt->readyTime <= curTick()) && (numReadDataReady > 0);
bool write_rdy = !pkt->isRead() && !ctrl->inReadBusState(true) &&
!writeRespQueueFull();
return (read_rdy || write_rdy);
}
std::pair<Tick, Tick>
NVMInterface::doBurstAccess(MemPacket* pkt, Tick next_burst_at)
{
DPRINTF(NVM, "NVM Timing access to addr %#x, rank/bank/row %d %d %d\n",
pkt->addr, pkt->rank, pkt->bank, pkt->row);
// get the bank
Bank& bank_ref = ranks[pkt->rank]->banks[pkt->bank];
// respect any constraints on the command
const Tick bst_allowed_at = pkt->isRead() ?
bank_ref.rdAllowedAt : bank_ref.wrAllowedAt;
// we need to wait until the bus is available before we can issue
// the command; need minimum of tBURST between commands
Tick cmd_at = std::max(bst_allowed_at, curTick());
// we need to wait until the bus is available before we can issue
// the command; need minimum of tBURST between commands
cmd_at = std::max(cmd_at, next_burst_at);
// Verify there is command bandwidth to issue
// Read burst (send command) is a simple data access and only requires
// one command cycle
// Write command may require multiple cycles to enable larger address space
if (pkt->isRead() || !twoCycleRdWr) {
cmd_at = ctrl->verifySingleCmd(cmd_at, maxCommandsPerWindow);
} else {
cmd_at = ctrl->verifyMultiCmd(cmd_at, maxCommandsPerWindow, tCK);
}
// update the packet ready time to reflect when data will be transferred
// Use the same bus delays defined for NVM
pkt->readyTime = cmd_at + tSEND + tBURST;
Tick dly_to_rd_cmd;
Tick dly_to_wr_cmd;
for (auto n : ranks) {
for (int i = 0; i < banksPerRank; i++) {
// base delay is a function of tBURST and bus turnaround
dly_to_rd_cmd = pkt->isRead() ? tBURST : writeToReadDelay();
dly_to_wr_cmd = pkt->isRead() ? readToWriteDelay() : tBURST;
if (pkt->rank != n->rank) {
// adjust timing for different ranks
// Need to account for rank-to-rank switching with tCS
dly_to_wr_cmd = rankToRankDelay();
dly_to_rd_cmd = rankToRankDelay();
}
n->banks[i].rdAllowedAt = std::max(cmd_at + dly_to_rd_cmd,
n->banks[i].rdAllowedAt);
n->banks[i].wrAllowedAt = std::max(cmd_at + dly_to_wr_cmd,
n->banks[i].wrAllowedAt);
}
}
DPRINTF(NVM, "NVM Access to %#x, ready at %lld.\n",
pkt->addr, pkt->readyTime);
if (pkt->isRead()) {
// completed the read, decrement counters
assert(numPendingReads != 0);
assert(numReadDataReady != 0);
numPendingReads--;
numReadDataReady--;
} else {
// Adjust number of NVM writes in Q
assert(numWritesQueued > 0);
numWritesQueued--;
// increment the bytes accessed and the accesses per row
// only increment for writes as the reads are handled when
// the non-deterministic read is issued, before the data transfer
bank_ref.bytesAccessed += burstSize;
// Commands will be issued serially when accessing the same bank
// Commands can issue in parallel to different banks
if ((bank_ref.bank == pkt->bank) &&
(bank_ref.openRow != pkt->row)) {
// update the open buffer, re-using row field
bank_ref.openRow = pkt->row;
// sample the bytes accessed to a buffer in this bank
// here when we are re-buffering the data
stats.bytesPerBank.sample(bank_ref.bytesAccessed);
// start counting anew
bank_ref.bytesAccessed = 0;
}
// Determine when write will actually complete, assuming it is
// scheduled to push to NVM immediately
// update actAllowedAt to serialize next command completion that
// accesses this bank; must wait until this write completes
// Data accesses to the same buffer in this bank
// can issue immediately after actAllowedAt expires, without
// waiting additional delay of tWRITE. Can revisit this
// assumption/simplification in the future.
bank_ref.actAllowedAt = std::max(pkt->readyTime,
bank_ref.actAllowedAt) + tWRITE;
// Need to track number of outstanding writes to
// ensure 'buffer' on media controller does not overflow
assert(!writeRespQueueFull());
// Insert into write done queue. It will be handled after
// the media delay has been met
if (writeRespQueueEmpty()) {
assert(!writeRespondEvent.scheduled());
schedule(writeRespondEvent, bank_ref.actAllowedAt);
} else {
assert(writeRespondEvent.scheduled());
}
writeRespQueue.push_back(bank_ref.actAllowedAt);
writeRespQueue.sort();
if (writeRespondEvent.when() > bank_ref.actAllowedAt) {
DPRINTF(NVM, "Rescheduled respond event from %lld to %11d\n",
writeRespondEvent.when(), bank_ref.actAllowedAt);
DPRINTF(NVM, "Front of response queue is %11d\n",
writeRespQueue.front());
reschedule(writeRespondEvent, bank_ref.actAllowedAt);
}
}
// Update the stats
if (pkt->isRead()) {
stats.readBursts++;
stats.bytesRead += burstSize;
stats.perBankRdBursts[pkt->bankId]++;
stats.pendingReads.sample(numPendingReads);
// Update latency stats
stats.totMemAccLat += pkt->readyTime - pkt->entryTime;
stats.totBusLat += tBURST;
stats.totQLat += cmd_at - pkt->entryTime;
} else {
stats.writeBursts++;
stats.bytesWritten += burstSize;
stats.perBankWrBursts[pkt->bankId]++;
}
return std::make_pair(cmd_at, cmd_at + tBURST);
}
void
NVMInterface::processWriteRespondEvent()
{
DPRINTF(NVM,
"processWriteRespondEvent(): A NVM write reached its readyTime. "
"%d remaining pending NVM writes\n", writeRespQueue.size());
// Update stat to track histogram of pending writes
stats.pendingWrites.sample(writeRespQueue.size());
// Done with this response, pop entry
writeRespQueue.pop_front();
if (!writeRespQueue.empty()) {
assert(writeRespQueue.front() >= curTick());
assert(!writeRespondEvent.scheduled());
schedule(writeRespondEvent, writeRespQueue.front());
}
// It is possible that a new command kicks things back into
// action before reaching this point but need to ensure that we
// continue to process new commands as writes complete at the media and
// credits become available. This will also trigger a drain if needed
if (!ctrl->requestEventScheduled()) {
DPRINTF(NVM, "Restart controller scheduler immediately\n");
ctrl->restartScheduler(curTick());
}
}
void
NVMInterface::addRankToRankDelay(Tick cmd_at)
{
// update timing for NVM ranks due to bursts issued
// to ranks for other media interfaces
for (auto n : ranks) {
for (int i = 0; i < banksPerRank; i++) {
// different rank by default
// Need to only account for rank-to-rank switching
n->banks[i].rdAllowedAt = std::max(cmd_at + rankToRankDelay(),
n->banks[i].rdAllowedAt);
n->banks[i].wrAllowedAt = std::max(cmd_at + rankToRankDelay(),
n->banks[i].wrAllowedAt);
}
}
}
bool
NVMInterface::isBusy(bool read_queue_empty, bool all_writes_nvm)
{
DPRINTF(NVM,"isBusy: numReadDataReady = %d\n", numReadDataReady);
// Determine NVM is busy and cannot issue a burst
// A read burst cannot issue when data is not ready from the NVM
// Also check that we have reads queued to ensure we can change
// bus direction to service potential write commands.
// A write cannot issue once we've reached MAX pending writes
// Only assert busy for the write case when there are also
// no reads in Q and the write queue only contains NVM commands
// This allows the bus state to switch and service reads
return (ctrl->inReadBusState(true) ?
(numReadDataReady == 0) && !read_queue_empty :
writeRespQueueFull() && read_queue_empty &&
all_writes_nvm);
}
NVMInterface::NVMStats::NVMStats(NVMInterface &_nvm)
: statistics::Group(&_nvm),
nvm(_nvm),
ADD_STAT(readBursts, statistics::units::Count::get(),
"Number of NVM read bursts"),
ADD_STAT(writeBursts, statistics::units::Count::get(),
"Number of NVM write bursts"),
ADD_STAT(perBankRdBursts, statistics::units::Count::get(),
"Per bank write bursts"),
ADD_STAT(perBankWrBursts, statistics::units::Count::get(),
"Per bank write bursts"),
ADD_STAT(totQLat, statistics::units::Tick::get(), "Total ticks spent queuing"),
ADD_STAT(totBusLat, statistics::units::Tick::get(),
"Total ticks spent in databus transfers"),
ADD_STAT(totMemAccLat, statistics::units::Tick::get(),
"Total ticks spent from burst creation until serviced "
"by the NVM"),
ADD_STAT(avgQLat, statistics::units::Rate<
statistics::units::Tick, statistics::units::Count>::get(),
"Average queueing delay per NVM burst"),
ADD_STAT(avgBusLat, statistics::units::Rate<
statistics::units::Tick, statistics::units::Count>::get(),
"Average bus latency per NVM burst"),
ADD_STAT(avgMemAccLat, statistics::units::Rate<
statistics::units::Tick, statistics::units::Count>::get(),
"Average memory access latency per NVM burst"),
ADD_STAT(avgRdBW, statistics::units::Rate<
statistics::units::Byte, statistics::units::Second>::get(),
"Average DRAM read bandwidth in MiBytes/s"),
ADD_STAT(avgWrBW, statistics::units::Rate<
statistics::units::Byte, statistics::units::Second>::get(),
"Average DRAM write bandwidth in MiBytes/s"),
ADD_STAT(peakBW, statistics::units::Rate<
statistics::units::Byte, statistics::units::Second>::get(),
"Theoretical peak bandwidth in MiByte/s"),
ADD_STAT(busUtil, statistics::units::Ratio::get(),
"NVM Data bus utilization in percentage"),
ADD_STAT(busUtilRead, statistics::units::Ratio::get(),
"NVM Data bus read utilization in percentage"),
ADD_STAT(busUtilWrite, statistics::units::Ratio::get(),
"NVM Data bus write utilization in percentage"),
ADD_STAT(pendingReads, statistics::units::Count::get(),
"Reads issued to NVM for which data has not been transferred"),
ADD_STAT(pendingWrites, statistics::units::Count::get(),
"Number of outstanding writes to NVM"),
ADD_STAT(bytesPerBank, statistics::units::Byte::get(),
"Bytes read within a bank before loading new bank")
{
}
void
NVMInterface::NVMStats::regStats()
{
using namespace statistics;
perBankRdBursts.init(nvm.ranksPerChannel == 0 ? 1 :
nvm.banksPerRank * nvm.ranksPerChannel);
perBankWrBursts.init(nvm.ranksPerChannel == 0 ? 1 :
nvm.banksPerRank * nvm.ranksPerChannel);
avgQLat.precision(2);
avgBusLat.precision(2);
avgMemAccLat.precision(2);
avgRdBW.precision(2);
avgWrBW.precision(2);
peakBW.precision(2);
busUtil.precision(2);
busUtilRead.precision(2);
busUtilWrite.precision(2);
pendingReads
.init(nvm.maxPendingReads)
.flags(nozero);
pendingWrites
.init(nvm.maxPendingWrites)
.flags(nozero);
bytesPerBank
.init(nvm.rowBufferSize)
.flags(nozero);
avgQLat = totQLat / readBursts;
avgBusLat = totBusLat / readBursts;
avgMemAccLat = totMemAccLat / readBursts;
avgRdBW = (bytesRead / 1000000) / simSeconds;
avgWrBW = (bytesWritten / 1000000) / simSeconds;
peakBW = (sim_clock::Frequency / nvm.tBURST) *
nvm.burstSize / 1000000;
busUtil = (avgRdBW + avgWrBW) / peakBW * 100;
busUtilRead = avgRdBW / peakBW * 100;
busUtilWrite = avgWrBW / peakBW * 100;
}
} // namespace memory
} // namespace gem5