minWritesPerSwitch(p->min_writes_per_switch),
writesThisTime(0), readsThisTime(0),
tWTR(p->tWTR), tRTW(p->tRTW), tBURST(p->tBURST),
- tRCD(p->tRCD), tCL(p->tCL), tRP(p->tRP), tRAS(p->tRAS),
+ tRCD(p->tRCD), tCL(p->tCL), tRP(p->tRP), tRAS(p->tRAS), tWR(p->tWR),
tRFC(p->tRFC), tREFI(p->tREFI), tRRD(p->tRRD),
tXAW(p->tXAW), activationLimit(p->activation_limit),
memSchedPolicy(p->mem_sched_policy), addrMapping(p->addr_mapping),
"tREFI %d ticks\n" \
"tWTR %d ticks\n" \
"tRTW %d ticks\n" \
+ "tWR %d ticks\n" \
"tXAW (%d) %d ticks\n",
name(), tRCD, tCL, tRP, tBURST, tRFC, tREFI, tWTR,
- tRTW, activationLimit, tXAW);
+ tRTW, tWR, activationLimit, tXAW);
}
void
Tick accLat = 0;
Tick bankLat = 0;
rowHitFlag = false;
- Tick potentialActTick;
const Bank& bank = dram_pkt->bankRef;
bankLat += tCL;
}
} else {
- // Row-buffer miss, need to close existing row
- // once tRAS has expired, then open the new one,
- // then add cas latency.
- Tick freeTime = std::max(bank.tRASDoneAt, bank.freeAt);
+ // Row-buffer miss, need to potentially close an existing row,
+ // then open the new one, then add CAS latency
+ Tick free_at = bank.freeAt;
+ Tick precharge_delay = 0;
- if (freeTime > inTime)
- accLat += freeTime - inTime;
+ // Check if we first need to precharge
+ if (bank.openRow != Bank::NO_ROW) {
+ free_at = std::max(bank.preAllowedAt, free_at);
+ precharge_delay = tRP;
+ }
- // If the there is no open row, then there is no precharge
- // delay, otherwise go with tRP
- Tick precharge_delay = bank.openRow == Bank::NO_ROW ? 0 : tRP;
+ // If the earliest time to issue the command is in the future,
+ // add it to the access latency
+ if (free_at > inTime)
+ accLat += free_at - inTime;
- //The bank is free, and you may be able to activate
- potentialActTick = inTime + accLat + precharge_delay;
- if (potentialActTick < bank.actAllowedAt)
- accLat += bank.actAllowedAt - potentialActTick;
+ // We also need to account for the earliest activation time,
+ // and potentially add that as well to the access latency
+ Tick act_at = inTime + accLat + precharge_delay;
+ if (act_at < bank.actAllowedAt)
+ accLat += bank.actAllowedAt - act_at;
accLat += precharge_delay + tRCD + tCL;
bankLat += precharge_delay + tRCD + tCL;
}
void
-DRAMCtrl::recordActivate(Tick act_tick, uint8_t rank, uint8_t bank,
- uint16_t row)
+DRAMCtrl::activateBank(Tick act_tick, uint8_t rank, uint8_t bank,
+ uint16_t row, Bank& bank_ref)
{
assert(0 <= rank && rank < ranksPerChannel);
assert(actTicks[rank].size() == activationLimit);
DPRINTF(DRAM, "Activate at tick %d\n", act_tick);
// update the open row
- assert(banks[rank][bank].openRow == Bank::NO_ROW);
- banks[rank][bank].openRow = 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
- banks[rank][bank].bytesAccessed = 0;
- banks[rank][bank].rowAccesses = 0;
+ bank_ref.bytesAccessed = 0;
+ bank_ref.rowAccesses = 0;
++numBanksActive;
assert(numBanksActive <= banksPerRank * ranksPerChannel);
// start by enforcing tRRD
for(int i = 0; i < banksPerRank; i++) {
- // next activate must not happen before tRRD
- banks[rank][i].actAllowedAt = act_tick + tRRD;
+ // next activate to any bank in this rank must not happen
+ // before tRRD
+ banks[rank][i].actAllowedAt = std::max(act_tick + tRRD,
+ banks[rank][i].actAllowedAt);
}
- // tRC should be added to activation tick of the bank currently accessed,
- // where tRC = tRAS + tRP, this is just for a check as actAllowedAt for same
- // bank is already captured by bank.freeAt and bank.tRASDoneAt
- banks[rank][bank].actAllowedAt = act_tick + tRAS + tRP;
-
// next, we deal with tXAW, if the activation limit is disabled
// then we are done
if (actTicks[rank].empty())
// sanity check
if (actTicks[rank].back() && (act_tick - actTicks[rank].back()) < tXAW) {
- // @todo For now, stick with a warning
- warn("Got %d activates in window %d (%d - %d) which is smaller "
- "than %d\n", activationLimit, act_tick - actTicks[rank].back(),
- act_tick, actTicks[rank].back(), tXAW);
+ panic("Got %d activates in window %d (%llu - %llu) which is smaller "
+ "than %llu\n", activationLimit, act_tick - actTicks[rank].back(),
+ act_tick, actTicks[rank].back(), tXAW);
}
// shift the times used for the book keeping, the last element
// oldest in our window of X
if (actTicks[rank].back() && (act_tick - actTicks[rank].back()) < tXAW) {
DPRINTF(DRAM, "Enforcing tXAW with X = %d, next activate no earlier "
- "than %d\n", activationLimit, actTicks[rank].back() + tXAW);
+ "than %llu\n", activationLimit, actTicks[rank].back() + tXAW);
for(int j = 0; j < banksPerRank; j++)
// next activate must not happen before end of window
- banks[rank][j].actAllowedAt = actTicks[rank].back() + tXAW;
+ banks[rank][j].actAllowedAt =
+ std::max(actTicks[rank].back() + tXAW,
+ banks[rank][j].actAllowedAt);
}
// at the point when this activate takes place, make sure we
// 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;
+ // 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);
+
Bank& bank = dram_pkt->bankRef;
// Update bank state
// If there is a page open, precharge it.
if (bank.openRow != Bank::NO_ROW) {
prechargeBank(bank, std::max(std::max(bank.freeAt,
- bank.tRASDoneAt),
+ bank.preAllowedAt),
curTick()) + tRP);
}
// any waiting for banks account for in freeAt
actTick = bank.freeAt - tCL - tRCD;
- // If you activated a new row do to this access, the next access
- // will have to respect tRAS for this bank
- bank.tRASDoneAt = actTick + tRAS;
+ // The next access has to respect tRAS for this bank
+ bank.preAllowedAt = actTick + tRAS;
- recordActivate(actTick, dram_pkt->rank, dram_pkt->bank,
- dram_pkt->row);
+ // Record the activation and deal with all the global timing
+ // constraints caused be a new activation (tRRD and tXAW)
+ activateBank(actTick, dram_pkt->rank, dram_pkt->bank,
+ dram_pkt->row, bank);
+
+ }
+
+ // If this is a write, we also need to respect the write
+ // recovery time before a precharge
+ if (!dram_pkt->isRead) {
+ bank.preAllowedAt = std::max(bank.preAllowedAt,
+ dram_pkt->readyTime + tWR);
}
+ // We also have to respect tRP, and any constraints on when we may
+ // precharge the bank, in the case of reads this is really only
+ // going to cause any change if we did not have a row hit and are
+ // now forced to respect tRAS
+ bank.actAllowedAt = std::max(bank.actAllowedAt,
+ bank.preAllowedAt + tRP);
+
// increment the bytes accessed and the accesses per row
bank.bytesAccessed += burstSize;
++bank.rowAccesses;
// if this access should use auto-precharge, then we are
// closing the row
if (auto_precharge) {
- prechargeBank(bank, std::max(bank.freeAt, bank.tRASDoneAt) + tRP);
+ prechargeBank(bank, std::max(bank.freeAt, bank.preAllowedAt) + tRP);
DPRINTF(DRAM, "Auto-precharged bank: %d\n", dram_pkt->bankId);
}
DPRINTF(DRAM, "doDRAMAccess::bank.freeAt is %lld\n", bank.freeAt);
- // 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;
// constraints
Tick free_at =
std::max(std::max(banks[i][j].freeAt,
- banks[i][j].tRASDoneAt),
+ banks[i][j].preAllowedAt),
curTick()) + tRP;
prechargeBank(banks[i][j], free_at);
std::vector<std::deque<Tick>> actTicks;
/**
- * A basic class to track the bank state indirectly via times
- * "freeAt" and "tRASDoneAt" and what page is currently open. The
- * bank also keeps track of how many bytes have been accessed in
- * the open row since it was opened.
+ * A basic class to track the bank state, i.e. what row is
+ * currently open (if any), when is the bank free to accept a new
+ * command, when can it be precharged, and when can it be
+ * activated.
+ *
+ * The bank also keeps track of how many bytes have been accessed
+ * in the open row since it was opened.
*/
class Bank
{
uint32_t openRow;
Tick freeAt;
- Tick tRASDoneAt;
+ Tick preAllowedAt;
Tick actAllowedAt;
uint32_t rowAccesses;
uint32_t bytesAccessed;
Bank() :
- openRow(NO_ROW), freeAt(0), tRASDoneAt(0), actAllowedAt(0),
+ openRow(NO_ROW), freeAt(0), preAllowedAt(0), actAllowedAt(0),
rowAccesses(0), bytesAccessed(0)
{ }
};
* the maximum number of activations in the activation window. The
* method updates the time that the banks become available based
* on the current limits.
+ *
+ * @param act_tick Time when the activation takes place
+ * @param rank Index of the rank
+ * @param bank Index of the bank
+ * @param row Index of the row
+ * @param bank_ref Reference to the bank
*/
- void recordActivate(Tick act_tick, uint8_t rank, uint8_t bank,
- uint16_t row);
+ void activateBank(Tick act_tick, uint8_t rank, uint8_t bank,
+ uint16_t row, Bank& bank_ref);
/**
* Precharge a given bank and also update when the precharge is
* accesses to the open page.
*
* @param bank The bank to precharge
- * @param free_at Time when the precharge is done
+ * @param pre_done_at Time when the precharge is done
*/
- void prechargeBank(Bank& bank, Tick free_at);
+ void prechargeBank(Bank& bank, Tick pre_done_at);
void printParams() const;
const Tick tCL;
const Tick tRP;
const Tick tRAS;
+ const Tick tWR;
const Tick tRFC;
const Tick tREFI;
const Tick tRRD;
projects / gem5.git / commitdiff