The memory controller is a single-channel memory controller capturing the most important timing constraints associated with a contemporary controller. More...

#include <mem_ctrl.hh>

Inheritance diagram for MemCtrl:

Classes
struct	CtrlStats

class	MemoryPort

Public Member Functions
	MemCtrl (const MemCtrlParams *p)

bool	allIntfDrained () const
	Ensure that all interfaced have drained commands. More...

DrainState	drain () override
	Draining is the process of clearing out the states of SimObjects.These are the SimObjects that are partially executed or are partially in flight. More...

Tick	verifySingleCmd (Tick cmd_tick, Tick max_cmds_per_burst)
	Check for command bus contention for single cycle command. More...

Tick	verifyMultiCmd (Tick cmd_tick, Tick max_cmds_per_burst, Tick max_multi_cmd_split=0)
	Check for command bus contention for multi-cycle (2 currently) command. More...

bool	respondEventScheduled () const
	Is there a respondEvent scheduled? More...

bool	requestEventScheduled () const
	Is there a read/write burst Event scheduled? More...

void	restartScheduler (Tick tick)
	restart the controller This can be used by interfaces to restart the scheduler after maintainence commands complete More...

bool	inReadBusState (bool next_state) const
	Check the current direction of the memory channel. More...

bool	inWriteBusState (bool next_state) const
	Check the current direction of the memory channel. More...

Port &	getPort (const std::string &if_name, PortID idx=InvalidPortID) override
	Get a port with a given name and index. More...

virtual void	init () override
	init() is called after all C++ SimObjects have been created and all ports are connected. More...

virtual void	startup () override
	startup() is the final initialization call before simulation. More...

virtual void	drainResume () override
	Resume execution after a successful drain. More...

Public Member Functions inherited from QoS::MemCtrl
	MemCtrl (const QoSMemCtrlParams *)
	QoS Memory base class. More...

virtual	~MemCtrl ()

BusState	getBusState () const
	Gets the current bus state. More...

BusState	getBusStateNext () const
	Gets the next bus state. More...

bool	hasRequestor (RequestorID id) const
	hasRequestor returns true if the selected requestor(ID) has been registered in the memory controller, which happens if the memory controller has received at least a packet from that requestor. More...

uint64_t	getReadQueueSize (const uint8_t prio) const
	Gets a READ queue size. More...

uint64_t	getWriteQueueSize (const uint8_t prio) const
	Gets a WRITE queue size. More...

uint64_t	getTotalReadQueueSize () const
	Gets the total combined READ queues size. More...

uint64_t	getTotalWriteQueueSize () const
	Gets the total combined WRITE queues size. More...

Tick	getServiceTick (const uint8_t prio) const
	Gets the last service tick related to a QoS Priority. More...

uint8_t	numPriorities () const
	Gets the total number of priority levels in the QoS memory controller. More...

System *	system () const
	read the system pointer More...

Public Member Functions inherited from ClockedObject
	ClockedObject (const ClockedObjectParams *p)

const Params *	params () const

void	serialize (CheckpointOut &cp) const override
	Serialize an object. More...

void	unserialize (CheckpointIn &cp) override
	Unserialize an object. More...

Public Member Functions inherited from SimObject
const Params *	params () const

	SimObject (const Params *_params)

virtual	~SimObject ()

virtual const std::string	name () const

virtual void	loadState (CheckpointIn &cp)
	loadState() is called on each SimObject when restoring from a checkpoint. More...

virtual void	initState ()
	initState() is called on each SimObject when not restoring from a checkpoint. More...

virtual void	regProbePoints ()
	Register probe points for this object. More...

virtual void	regProbeListeners ()
	Register probe listeners for this object. More...

ProbeManager *	getProbeManager ()
	Get the probe manager for this object. More...

DrainState	drain () override
	Provide a default implementation of the drain interface for objects that don't need draining. More...

virtual void	memWriteback ()
	Write back dirty buffers to memory using functional writes. More...

virtual void	memInvalidate ()
	Invalidate the contents of memory buffers. More...

void	serialize (CheckpointOut &cp) const override
	Serialize an object. More...

void	unserialize (CheckpointIn &cp) override
	Unserialize an object. More...

Public Member Functions inherited from EventManager
EventQueue *	eventQueue () const

void	schedule (Event &event, Tick when)

void	deschedule (Event &event)

void	reschedule (Event &event, Tick when, bool always=false)

void	schedule (Event *event, Tick when)

void	deschedule (Event *event)

void	reschedule (Event *event, Tick when, bool always=false)

void	wakeupEventQueue (Tick when=(Tick) -1)
	This function is not needed by the usual gem5 event loop but may be necessary in derived EventQueues which host gem5 on other schedulers. More...

void	setCurTick (Tick newVal)

	EventManager (EventManager &em)
	Event manger manages events in the event queue. More...

	EventManager (EventManager *em)

	EventManager (EventQueue *eq)

Public Member Functions inherited from Serializable
	Serializable ()

virtual	~Serializable ()

void	serializeSection (CheckpointOut &cp, const char *name) const
	Serialize an object into a new section. More...

void	serializeSection (CheckpointOut &cp, const std::string &name) const

void	unserializeSection (CheckpointIn &cp, const char *name)
	Unserialize an a child object. More...

void	unserializeSection (CheckpointIn &cp, const std::string &name)

Public Member Functions inherited from Drainable
DrainState	drainState () const
	Return the current drain state of an object. More...

virtual void	notifyFork ()
	Notify a child process of a fork. More...

Public Member Functions inherited from Stats::Group
	Group (Group parent, const char name=nullptr)
	Construct a new statistics group. More...

virtual	~Group ()

virtual void	regStats ()
	Callback to set stat parameters. More...

virtual void	resetStats ()
	Callback to reset stats. More...

virtual void	preDumpStats ()
	Callback before stats are dumped. More...

void	addStat (Stats::Info *info)
	Register a stat with this group. More...

const std::map< std::string, Group * > &	getStatGroups () const
	Get all child groups associated with this object. More...

const std::vector< Info * > &	getStats () const
	Get all stats associated with this object. More...

void	addStatGroup (const char name, Group block)
	Add a stat block as a child of this block. More...

const Info *	resolveStat (std::string name) const
	Resolve a stat by its name within this group. More...

	Group ()=delete

	Group (const Group &)=delete

Group &	operator= (const Group &)=delete

Public Member Functions inherited from Clocked
void	updateClockPeriod ()
	Update the tick to the current tick. More...

Tick	clockEdge (Cycles cycles=Cycles(0)) const
	Determine the tick when a cycle begins, by default the current one, but the argument also enables the caller to determine a future cycle. More...

Cycles	curCycle () const
	Determine the current cycle, corresponding to a tick aligned to a clock edge. More...

Tick	nextCycle () const
	Based on the clock of the object, determine the start tick of the first cycle that is at least one cycle in the future. More...

uint64_t	frequency () const

Tick	clockPeriod () const

double	voltage () const

Cycles	ticksToCycles (Tick t) const

Tick	cyclesToTicks (Cycles c) const

Protected Member Functions
Tick	recvAtomic (PacketPtr pkt)

void	recvFunctional (PacketPtr pkt)

bool	recvTimingReq (PacketPtr pkt)

Protected Member Functions inherited from QoS::MemCtrl
void	addRequestor (const RequestorID id)
	Initializes dynamically counters and statistics for a given Requestor. More...

void	logRequest (BusState dir, RequestorID id, uint8_t qos, Addr addr, uint64_t entries)
	Called upon receiving a request or updates statistics and updates queues status. More...

void	logResponse (BusState dir, RequestorID id, uint8_t qos, Addr addr, uint64_t entries, double delay)
	Called upon receiving a response, updates statistics and updates queues status. More...

template<typename Queues >
uint8_t	qosSchedule (std::initializer_list< Queues * > queues_ptr, uint64_t queue_entry_size, const PacketPtr pkt)
	Assign priority to a packet by executing the configured QoS policy. More...

uint8_t	schedule (RequestorID id, uint64_t data)

uint8_t	schedule (const PacketPtr pkt)

BusState	selectNextBusState ()
	Returns next bus direction (READ or WRITE) based on configured policy. More...

void	setCurrentBusState ()
	Set current bus direction (READ or WRITE) from next selected one. More...

void	recordTurnaroundStats ()
	Record statistics on turnarounds based on busStateNext and busState values. More...

template<typename Queues >
void	escalate (std::initializer_list< Queues * > queues, uint64_t queue_entry_size, RequestorID id, uint8_t tgt_prio)
	Escalates/demotes priority of all packets belonging to the passed requestor to given priority value. More...

template<typename Queues >
void	escalateQueues (Queues &queues, uint64_t queue_entry_size, RequestorID id, uint8_t curr_prio, uint8_t tgt_prio)
	Escalates/demotes priority of all packets belonging to the passed requestor to given priority value in a specified cluster of queues (e.g. More...

Protected Member Functions inherited from Drainable
	Drainable ()

virtual	~Drainable ()

void	signalDrainDone () const
	Signal that an object is drained. More...

Protected Member Functions inherited from Clocked
	Clocked (ClockDomain &clk_domain)
	Create a clocked object and set the clock domain based on the parameters. More...

	Clocked (Clocked &)=delete

Clocked &	operator= (Clocked &)=delete

virtual	~Clocked ()
	Virtual destructor due to inheritance. More...

void	resetClock () const
	Reset the object's clock using the current global tick value. More...

virtual void	clockPeriodUpdated ()
	A hook subclasses can implement so they can do any extra work that's needed when the clock rate is changed. More...

Private Member Functions
void	processNextReqEvent ()
	Bunch of things requires to setup "events" in gem5 When event "respondEvent" occurs for example, the method processRespondEvent is called; no parameters are allowed in these methods. More...

void	processRespondEvent ()

bool	readQueueFull (unsigned int pkt_count) const
	Check if the read queue has room for more entries. More...

bool	writeQueueFull (unsigned int pkt_count) const
	Check if the write queue has room for more entries. More...

void	addToReadQueue (PacketPtr pkt, unsigned int pkt_count, bool is_dram)
	When a new read comes in, first check if the write q has a pending request to the same address. If not, decode the address to populate rank/bank/row, create one or mutliple "mem_pkt", and push them to the back of the read queue. More...

void	addToWriteQueue (PacketPtr pkt, unsigned int pkt_count, bool is_dram)
	Decode the incoming pkt, create a mem_pkt and push to the back of the write queue. More...

void	doBurstAccess (MemPacket *mem_pkt)
	Actually do the burst based on media specific access function. More...

void	accessAndRespond (PacketPtr pkt, Tick static_latency)
	When a packet reaches its "readyTime" in the response Q, use the "access()" method in AbstractMemory to actually create the response packet, and send it back to the outside world requestor. More...

bool	packetReady (MemPacket *pkt)
	Determine if there is a packet that can issue. More...

Tick	minReadToWriteDataGap ()
	Calculate the minimum delay used when scheduling a read-to-write transision. More...

Tick	minWriteToReadDataGap ()
	Calculate the minimum delay used when scheduling a write-to-read transision. More...

MemPacketQueue::iterator	chooseNext (MemPacketQueue &queue, Tick extra_col_delay)
	The memory schduler/arbiter - picks which request needs to go next, based on the specified policy such as FCFS or FR-FCFS and moves it to the head of the queue. More...

MemPacketQueue::iterator	chooseNextFRFCFS (MemPacketQueue &queue, Tick extra_col_delay)
	For FR-FCFS policy reorder the read/write queue depending on row buffer hits and earliest bursts available in memory. More...

Tick	getBurstWindow (Tick cmd_tick)
	Calculate burst window aligned tick. More...

void	printQs () const
	Used for debugging to observe the contents of the queues. More...

Addr	burstAlign (Addr addr, bool is_dram) const
	Burst-align an address. More...

std::vector< MemPacketQueue > &	selQueue (bool is_read)
	Select either the read or write queue. More...

void	pruneBurstTick ()
	Remove commands that have already issued from burstTicks. More...

Private Attributes
MemoryPort	port
	Our incoming port, for a multi-ported controller add a crossbar in front of it. More...

bool	isTimingMode
	Remember if the memory system is in timing mode. More...

bool	retryRdReq
	Remember if we have to retry a request when available. More...

bool	retryWrReq

EventFunctionWrapper	nextReqEvent

EventFunctionWrapper	respondEvent

std::vector< MemPacketQueue >	readQueue
	The controller's main read and write queues, with support for QoS reordering. More...

std::vector< MemPacketQueue >	writeQueue

std::unordered_set< Addr >	isInWriteQueue
	To avoid iterating over the write queue to check for overlapping transactions, maintain a set of burst addresses that are currently queued. More...

std::deque< MemPacket * >	respQueue
	Response queue where read packets wait after we're done working with them, but it's not time to send the response yet. More...

std::unordered_multiset< Tick >	burstTicks
	Holds count of commands issued in burst window starting at defined Tick. More...

DRAMInterface *const	dram
	Create pointer to interface of the actual dram media when connected. More...

NVMInterface *const	nvm
	Create pointer to interface of the actual nvm media when connected. More...

const uint32_t	readBufferSize
	The following are basic design parameters of the memory controller, and are initialized based on parameter values. More...

const uint32_t	writeBufferSize

const uint32_t	writeHighThreshold

const uint32_t	writeLowThreshold

const uint32_t	minWritesPerSwitch

uint32_t	writesThisTime

uint32_t	readsThisTime

Enums::MemSched	memSchedPolicy
	Memory controller configuration initialized based on parameter values. More...

const Tick	frontendLatency
	Pipeline latency of the controller frontend. More...

const Tick	backendLatency
	Pipeline latency of the backend and PHY. More...

const Tick	commandWindow
	Length of a command window, used to check command bandwidth. More...

Tick	nextBurstAt
	Till when must we wait before issuing next RD/WR burst? More...

Tick	prevArrival

Tick	nextReqTime
	The soonest you have to start thinking about the next request is the longest access time that can occur before nextBurstAt. More...

CtrlStats	stats

std::unique_ptr< Packet >	pendingDelete
	Upstream caches need this packet until true is returned, so hold it for deletion until a subsequent call. More...

Additional Inherited Members
Public Types inherited from QoS::MemCtrl
enum	BusState { READ, WRITE }
	Bus Direction. More...

Public Types inherited from ClockedObject
typedef ClockedObjectParams	Params
	Parameters of ClockedObject. More...

Public Types inherited from SimObject
typedef SimObjectParams	Params

Static Public Member Functions inherited from SimObject
static void	serializeAll (CheckpointOut &cp)
	Serialize all SimObjects in the system. More...

static SimObject *	find (const char *name)
	Find the SimObject with the given name and return a pointer to it. More...

Static Public Member Functions inherited from Serializable
static const std::string &	currentSection ()
	Gets the fully-qualified name of the active section. More...

static void	serializeAll (const std::string &cpt_dir)
	Serializes all the SimObjects. More...

static void	unserializeGlobals (CheckpointIn &cp)

Public Attributes inherited from ClockedObject
PowerState *	powerState

Protected Attributes inherited from QoS::MemCtrl
const std::unique_ptr< Policy >	policy
	QoS Policy, assigns QoS priority to the incoming packets. More...

const std::unique_ptr< TurnaroundPolicy >	turnPolicy
	QoS Bus Turnaround Policy: selects the bus direction (READ/WRITE) More...

const std::unique_ptr< QueuePolicy >	queuePolicy
	QoS Queue Policy: selects packet among same-priority queue. More...

const uint8_t	_numPriorities
	Number of configured QoS priorities. More...

const bool	qosPriorityEscalation
	Enables QoS priority escalation. More...

const bool	qosSyncroScheduler
	Enables QoS synchronized scheduling invokes the QoS scheduler on all requestors, at every packet arrival. More...

std::unordered_map< RequestorID, const std::string >	requestors
	Hash of requestor ID - requestor name. More...

std::unordered_map< RequestorID, std::vector< uint64_t > >	packetPriorities
	Hash of requestors - number of packets queued per priority. More...

std::unordered_map< RequestorID, std::unordered_map< uint64_t, std::deque< uint64_t > > >	requestTimes
	Hash of requestors - address of request - queue of times of request. More...

std::vector< Tick >	serviceTick
	Vector of QoS priorities/last service time. More...

std::vector< uint64_t >	readQueueSizes
	Read request packets queue length in #packets, per QoS priority. More...

std::vector< uint64_t >	writeQueueSizes
	Write request packets queue length in #packets, per QoS priority. More...

uint64_t	totalReadQueueSize
	Total read request packets queue length in #packets. More...

uint64_t	totalWriteQueueSize
	Total write request packets queue length in #packets. More...

BusState	busState
	Bus state used to control the read/write switching and drive the scheduling of the next request. More...

BusState	busStateNext
	bus state for next request event triggered More...

QoS::MemCtrl::MemCtrlStats	stats

System *	_system
	Pointer to the System object. More...

Protected Attributes inherited from SimObject
const SimObjectParams *	_params
	Cached copy of the object parameters. More...

Protected Attributes inherited from EventManager
EventQueue *	eventq
	A pointer to this object's event queue. More...

Detailed Description

The memory controller is a single-channel memory controller capturing the most important timing constraints associated with a contemporary controller.

For multi-channel memory systems, the controller is combined with a crossbar model, with the channel address interleaving taking part in the crossbar.

As a basic design principle, this controller model is not cycle callable, but instead uses events to: 1) decide when new decisions can be made, 2) when resources become available, 3) when things are to be considered done, and 4) when to send things back. The controller interfaces to media specific interfaces to enable flexible topoloties. Through these simple principles, the model delivers high performance, and lots of flexibility, allowing users to evaluate the system impact of a wide range of memory technologies.

For more details, please see Hansson et al, "Simulating DRAM controllers for future system architecture exploration", Proc. ISPASS, 2014. If you use this model as part of your research please cite the paper.

Definition at line 236 of file mem_ctrl.hh.

Constructor & Destructor Documentation

◆ MemCtrl()

MemCtrl::MemCtrl ( const MemCtrlParams * p )

Definition at line 54 of file mem_ctrl.cc.

References processNextReqEvent().

Member Function Documentation

◆ accessAndRespond()

void MemCtrl::accessAndRespond	(	PacketPtr	pkt,
		Tick	static_latency
	)

private

When a packet reaches its "readyTime" in the response Q, use the "access()" method in AbstractMemory to actually create the response packet, and send it back to the outside world requestor.

Parameters

pkt	The packet from the outside world
static_latency	Static latency to add before sending the packet

Definition at line 622 of file mem_ctrl.cc.

References AbstractMemory::access(), AddrRange::contains(), curTick(), DPRINTF, dram, Packet::getAddr(), AbstractMemory::getAddrRange(), Packet::headerDelay, Packet::isResponse(), Packet::needsResponse(), nvm, panic, Packet::payloadDelay, pendingDelete, port, Packet::print(), and QueuedResponsePort::schedTimingResp().

Referenced by addToReadQueue(), addToWriteQueue(), and processRespondEvent().

◆ addToReadQueue()

void MemCtrl::addToReadQueue	(	PacketPtr	pkt,
		unsigned int	pkt_count,
		bool	is_dram
	)

private

When a new read comes in, first check if the write q has a pending request to the same address. If not, decode the address to populate rank/bank/row, create one or mutliple "mem_pkt", and push them to the back of the read queue.

\ If this is the only read request in the system, schedule an event to start servicing it.

Parameters

pkt	The request packet from the outside world
pkt_count	The number of memory bursts the pkt
is_dram	Does this packet access DRAM? translate to. If pkt size is larger then one full burst, then pkt_count is greater than one.

Definition at line 181 of file mem_ctrl.cc.

References accessAndRespond(), MemPacket::addr, addr, MemCtrl::CtrlStats::avgRdQLen, burstAlign(), MemPacket::burstHelper, BurstHelper::burstsServiced, MemInterface::bytesPerBurst(), MemCtrl::CtrlStats::bytesReadWrQ, ceilLog2(), curTick(), MemInterface::decodePacket(), DPRINTF, dram, frontendLatency, Packet::getAddr(), Packet::getSize(), isInWriteQueue, Packet::isWrite(), QoS::MemCtrl::logRequest(), MaxTick, nextReqEvent, nvm, MipsISA::p, MemPacket::qosValue(), Packet::qosValue(), MemPacket::rank, MemCtrl::CtrlStats::rdQLenPdf, QoS::MemCtrl::READ, MemCtrl::CtrlStats::readBursts, MemCtrl::CtrlStats::readPktSize, readQueue, readQueueFull(), MemPacket::readyTime, Packet::requestorId(), MemCtrl::CtrlStats::requestorReadAccesses, respQueue, QoS::MemCtrl::schedule(), Event::scheduled(), MemCtrl::CtrlStats::servicedByWrQ, DRAMInterface::setupRank(), NVMInterface::setupRank(), stats, QoS::MemCtrl::totalReadQueueSize, and writeQueue.

Referenced by recvTimingReq().

◆ addToWriteQueue()

void MemCtrl::addToWriteQueue	(	PacketPtr	pkt,
		unsigned int	pkt_count,
		bool	is_dram
	)

private

Decode the incoming pkt, create a mem_pkt and push to the back of the write queue.

\If the write q length is more than the threshold specified by the user, ie the queue is beginning to get full, stop reads, and start draining writes.

Parameters

pkt	The request packet from the outside world
pkt_count	The number of memory bursts the pkt
is_dram	Does this packet access DRAM? translate to. If pkt size is larger then one full burst, then pkt_count is greater than one.

Definition at line 300 of file mem_ctrl.cc.

References accessAndRespond(), MemPacket::addr, addr, MemCtrl::CtrlStats::avgWrQLen, burstAlign(), MemInterface::bytesPerBurst(), ceilLog2(), curTick(), MemInterface::decodePacket(), DPRINTF, dram, frontendLatency, Packet::getAddr(), Packet::getSize(), isInWriteQueue, Packet::isWrite(), QoS::MemCtrl::logRequest(), MemCtrl::CtrlStats::mergedWrBursts, nextReqEvent, nvm, MemPacket::qosValue(), Packet::qosValue(), MemPacket::rank, Packet::requestorId(), MemCtrl::CtrlStats::requestorWriteAccesses, QoS::MemCtrl::schedule(), Event::scheduled(), DRAMInterface::setupRank(), NVMInterface::setupRank(), stats, QoS::MemCtrl::totalWriteQueueSize, QoS::MemCtrl::WRITE, writeBufferSize, MemCtrl::CtrlStats::writeBursts, MemCtrl::CtrlStats::writePktSize, writeQueue, and MemCtrl::CtrlStats::wrQLenPdf.

Referenced by recvTimingReq().

◆ allIntfDrained()

bool MemCtrl::allIntfDrained ( ) const

Ensure that all interfaced have drained commands.

Returns: bool flag, set once drain complete

Definition at line 1367 of file mem_ctrl.cc.

References DRAMInterface::allRanksDrained(), NVMInterface::allRanksDrained(), dram, and nvm.

Referenced by drain(), processNextReqEvent(), and processRespondEvent().

◆ burstAlign()

Addr MemCtrl::burstAlign	(	Addr	addr,
		bool	is_dram
	)		const

private

Burst-align an address.

Parameters

addr	The potentially unaligned address
is_dram	Does this packet access DRAM?

Returns: An address aligned to a memory burst

Definition at line 1166 of file mem_ctrl.cc.

References addr, MemInterface::bytesPerBurst(), dram, and nvm.

Referenced by addToReadQueue(), addToWriteQueue(), and processNextReqEvent().

◆ chooseNext()

MemPacketQueue::iterator MemCtrl::chooseNext	(	MemPacketQueue &	queue,
		Tick	extra_col_delay
	)

private

The memory schduler/arbiter - picks which request needs to go next, based on the specified policy such as FCFS or FR-FCFS and moves it to the head of the queue.

Prioritizes accesses to the same rank as previous burst unless controller is switching command type.

Parameters

queue	Queued requests to consider
extra_col_delay	Any extra delay due to a read/write switch

Returns: an iterator to the selected packet, else queue.end()

Definition at line 545 of file mem_ctrl.cc.

References chooseNextFRFCFS(), DPRINTF, ArmISA::i, memSchedPolicy, packetReady(), and panic.

Referenced by processNextReqEvent().

◆ chooseNextFRFCFS()

MemPacketQueue::iterator MemCtrl::chooseNextFRFCFS	(	MemPacketQueue &	queue,
		Tick	extra_col_delay
	)

private

For FR-FCFS policy reorder the read/write queue depending on row buffer hits and earliest bursts available in memory.

Parameters

queue	Queued requests to consider
extra_col_delay	Any extra delay due to a read/write switch

Returns: an iterator to the selected packet, else queue.end()

Definition at line 580 of file mem_ctrl.cc.

References DRAMInterface::chooseNextFRFCFS(), NVMInterface::chooseNextFRFCFS(), curTick(), DPRINTF, dram, MaxTick, nextBurstAt, and nvm.

Referenced by chooseNext().

◆ doBurstAccess()

void MemCtrl::doBurstAccess ( MemPacket * mem_pkt )

private

Actually do the burst based on media specific access function.

Update bus statistics when complete.

Parameters

mem_pkt The memory packet created from the outside world pkt

Definition at line 800 of file mem_ctrl.cc.

References MemPacket::addr, DRAMInterface::addRankToRankDelay(), NVMInterface::addRankToRankDelay(), DRAMInterface::commandOffset(), NVMInterface::commandOffset(), DRAMInterface::doBurstAccess(), NVMInterface::doBurstAccess(), DPRINTF, dram, MemPacket::entryTime, MemPacket::isDram(), MemPacket::isRead(), nextBurstAt, nextReqTime, nvm, pruneBurstTick(), readsThisTime, MemPacket::readyTime, MemPacket::requestorId(), MemCtrl::CtrlStats::requestorReadBytes, MemCtrl::CtrlStats::requestorReadTotalLat, MemCtrl::CtrlStats::requestorWriteBytes, MemCtrl::CtrlStats::requestorWriteTotalLat, selQueue(), MemPacket::size, stats, and writesThisTime.

Referenced by processNextReqEvent().

◆ drain()

DrainState MemCtrl::drain ( )

overridevirtual

Draining is the process of clearing out the states of SimObjects.These are the SimObjects that are partially executed or are partially in flight.

Draining is mostly used before forking and creating a check point.

This function notifies an object that it needs to drain its state.

If the object does not need further simulation to drain internal buffers, it returns DrainState::Drained and automatically switches to the Drained state. If the object needs more simulation, it returns DrainState::Draining and automatically enters the Draining state. Other return values are invalid.

Note: An object that has entered the Drained state can be disturbed by other objects in the system and consequently stop being drained. These perturbations are not visible in the drain state. The simulator therefore repeats the draining process until all objects return DrainState::Drained on the first call to drain().

Returns: DrainState::Drained if the object is drained at this point in time, DrainState::Draining if it needs further simulation.

Implements Drainable.

Definition at line 1378 of file mem_ctrl.cc.

References allIntfDrained(), curTick(), DPRINTF, Drained, Draining, DRAMInterface::drainRanks(), dram, nextReqEvent, respQueue, QoS::MemCtrl::schedule(), Event::scheduled(), QoS::MemCtrl::totalReadQueueSize, and QoS::MemCtrl::totalWriteQueueSize.

◆ drainResume()

void MemCtrl::drainResume ( )

overridevirtual

Resume execution after a successful drain.

Reimplemented from Drainable.

Definition at line 1405 of file mem_ctrl.cc.

References dram, System::isTimingMode(), isTimingMode, startup(), DRAMInterface::startup(), DRAMInterface::suspend(), and QoS::MemCtrl::system().

◆ getBurstWindow()

Tick MemCtrl::getBurstWindow ( Tick cmd_tick )

private

Calculate burst window aligned tick.

Parameters

cmd_tick Initial tick of command

Returns: burst window aligned tick

Definition at line 679 of file mem_ctrl.cc.

References commandWindow.

Referenced by verifyMultiCmd(), and verifySingleCmd().

◆ getPort()

Port & MemCtrl::getPort	(	const std::string &	if_name,
		PortID	idx = `InvalidPortID`
	)

overridevirtual

Get a port with a given name and index.

This is used at binding time and returns a reference to a protocol-agnostic port.

gem5 has a request and response port interface. All memory objects are connected together via ports. These ports provide a rigid interface between these memory objects. These ports implement three different memory system modes: timing, atomic, and functional. The most important mode is the timing mode and here timing mode is used for conducting cycle-level timing experiments. The other modes are only used in special circumstances and should not be used to conduct cycle-level timing experiments. The other modes are only used in special circumstances. These ports allow SimObjects to communicate with each other.

Parameters

if_name	Port name
idx	Index in the case of a VectorPort

Returns: A reference to the given port

Reimplemented from SimObject.

Definition at line 1357 of file mem_ctrl.cc.

References SimObject::getPort(), and port.

◆ init()

void MemCtrl::init ( )

overridevirtual

init() is called after all C++ SimObjects have been created and all ports are connected.

Initializations that are independent of unserialization but rely on a fully instantiated and connected SimObject graph should be done here.

Reimplemented from SimObject.

Definition at line 97 of file mem_ctrl.cc.

References fatal, Port::isConnected(), SimObject::name(), port, and ResponsePort::sendRangeChange().

◆ inReadBusState()

bool MemCtrl::inReadBusState ( bool next_state ) const

Check the current direction of the memory channel.

Parameters

next_state Check either the current or next bus state

Returns: True when bus is currently in a read state

Definition at line 774 of file mem_ctrl.cc.

References QoS::MemCtrl::busState, QoS::MemCtrl::busStateNext, and QoS::MemCtrl::READ.

Referenced by NVMInterface::burstReady(), NVMInterface::isBusy(), and DRAMInterface::minBankPrep().

◆ inWriteBusState()

bool MemCtrl::inWriteBusState ( bool next_state ) const

Check the current direction of the memory channel.

Parameters

next_state Check either the current or next bus state

Returns: True when bus is currently in a write state

Definition at line 787 of file mem_ctrl.cc.

References QoS::MemCtrl::busState, QoS::MemCtrl::busStateNext, and QoS::MemCtrl::WRITE.

◆ minReadToWriteDataGap()

Tick MemCtrl::minReadToWriteDataGap ( )

private

Calculate the minimum delay used when scheduling a read-to-write transision.

Parameters

return minimum delay

Definition at line 1150 of file mem_ctrl.cc.

References dram, MaxTick, MemInterface::minReadToWriteDataGap(), and nvm.

Referenced by processNextReqEvent().

◆ minWriteToReadDataGap()

Tick MemCtrl::minWriteToReadDataGap ( )

private

Calculate the minimum delay used when scheduling a write-to-read transision.

Parameters

return minimum delay

Definition at line 1158 of file mem_ctrl.cc.

References dram, MaxTick, MemInterface::minWriteToReadDataGap(), and nvm.

Referenced by processNextReqEvent().

◆ packetReady()

bool MemCtrl::packetReady ( MemPacket * pkt )

private

Determine if there is a packet that can issue.

Parameters

pkt	The packet to evaluate

Definition at line 1143 of file mem_ctrl.cc.

References DRAMInterface::burstReady(), NVMInterface::burstReady(), dram, MemPacket::isDram(), and nvm.

Referenced by chooseNext().

◆ printQs()

void MemCtrl::printQs ( ) const

private

Used for debugging to observe the contents of the queues.

Definition at line 381 of file mem_ctrl.cc.

References DPRINTF, readQueue, respQueue, and writeQueue.

◆ processNextReqEvent()

void MemCtrl::processNextReqEvent ( )

private

Bunch of things requires to setup "events" in gem5 When event "respondEvent" occurs for example, the method processRespondEvent is called; no parameters are allowed in these methods.

Definition at line 857 of file mem_ctrl.cc.

References allIntfDrained(), burstAlign(), QoS::MemCtrl::busState, QoS::MemCtrl::busStateNext, MemInterface::bytesPerBurst(), chooseNext(), NVMInterface::chooseRead(), curTick(), doBurstAccess(), DPRINTF, Draining, Drainable::drainState(), dram, DRAMInterface::isBusy(), NVMInterface::isBusy(), isInWriteQueue, QoS::MemCtrl::logResponse(), minReadToWriteDataGap(), minWritesPerSwitch, minWriteToReadDataGap(), nextReqEvent, nextReqTime, QoS::MemCtrl::numPriorities(), NVMInterface::numWritesQueued, nvm, port, MemCtrl::CtrlStats::rdPerTurnAround, QoS::MemCtrl::READ, readQueue, readsThisTime, NVMInterface::readsWaitingToIssue(), QoS::MemCtrl::recordTurnaroundStats(), respondEvent, respQueue, retryWrReq, Stats::DistBase< Derived, Stor >::sample(), QoS::MemCtrl::schedule(), Event::scheduled(), QoS::MemCtrl::selectNextBusState(), ResponsePort::sendRetryReq(), Drainable::signalDrainDone(), stats, QoS::MemCtrl::totalReadQueueSize, QoS::MemCtrl::totalWriteQueueSize, QoS::MemCtrl::turnPolicy, QoS::MemCtrl::WRITE, writeBufferSize, writeHighThreshold, writeLowThreshold, writeQueue, NVMInterface::writeRespQueueFull(), writesThisTime, and MemCtrl::CtrlStats::wrPerTurnAround.

Referenced by MemCtrl().

◆ processRespondEvent()

void MemCtrl::processRespondEvent ( )

private

◆ pruneBurstTick()

void MemCtrl::pruneBurstTick ( )

private

Remove commands that have already issued from burstTicks.

Definition at line 666 of file mem_ctrl.cc.

References burstTicks, curTick(), and DPRINTF.

Referenced by doBurstAccess().

◆ readQueueFull()

bool MemCtrl::readQueueFull ( unsigned int pkt_count ) const

private

Check if the read queue has room for more entries.

Parameters

pkt_count The number of entries needed in the read queue

Returns: true if read queue is full, false otherwise

Definition at line 158 of file mem_ctrl.cc.

References DPRINTF, readBufferSize, respQueue, and QoS::MemCtrl::totalReadQueueSize.

Referenced by addToReadQueue(), and recvTimingReq().

◆ recvAtomic()

Tick MemCtrl::recvAtomic ( PacketPtr pkt )

protected

Definition at line 123 of file mem_ctrl.cc.

References AbstractMemory::access(), DRAMInterface::accessLatency(), NVMInterface::accessLatency(), Packet::cacheResponding(), Packet::cmdString(), AddrRange::contains(), DPRINTF, dram, Packet::getAddr(), AbstractMemory::getAddrRange(), Packet::hasData(), nvm, panic, panic_if, and Packet::print().

◆ recvFunctional()

void MemCtrl::recvFunctional ( PacketPtr pkt )

protected

Definition at line 1342 of file mem_ctrl.cc.

References AddrRange::contains(), dram, AbstractMemory::functionalAccess(), Packet::getAddr(), AbstractMemory::getAddrRange(), nvm, panic, and Packet::print().

◆ recvTimingReq()

bool MemCtrl::recvTimingReq ( PacketPtr pkt )

protected

◆ requestEventScheduled()

bool MemCtrl::requestEventScheduled ( ) const

inline

Is there a read/write burst Event scheduled?

Returns: true if event is scheduled

Definition at line 667 of file mem_ctrl.hh.

References nextReqEvent, and Event::scheduled().

Referenced by NVMInterface::processReadReadyEvent(), and NVMInterface::processWriteRespondEvent().

◆ respondEventScheduled()

bool MemCtrl::respondEventScheduled ( ) const

inline

Is there a respondEvent scheduled?

Returns: true if event is scheduled

Definition at line 660 of file mem_ctrl.hh.

References respondEvent, and Event::scheduled().

◆ restartScheduler()

void MemCtrl::restartScheduler ( Tick tick )

inline

restart the controller This can be used by interfaces to restart the scheduler after maintainence commands complete

Parameters

Tick	to schedule next event

Definition at line 676 of file mem_ctrl.hh.

References nextReqEvent, QoS::MemCtrl::schedule(), and Clocked::tick.

Referenced by NVMInterface::processReadReadyEvent(), and NVMInterface::processWriteRespondEvent().

◆ selQueue()

std::vector<MemPacketQueue>& MemCtrl::selQueue ( bool is_read )

inlineprivate

Select either the read or write queue.

Parameters

is_read The current burst is a read, select read queue

Returns: a reference to the appropriate queue

Definition at line 600 of file mem_ctrl.hh.

References readQueue, and writeQueue.

Referenced by doBurstAccess().

◆ startup()

void MemCtrl::startup ( )

overridevirtual

startup() is the final initialization call before simulation.

All state is initialized (including unserialized state, if any, such as the curTick() value), so this is the appropriate place to schedule initial event(s) for objects that need them.

Reimplemented from SimObject.

Definition at line 107 of file mem_ctrl.cc.

References DRAMInterface::commandOffset(), NVMInterface::commandOffset(), curTick(), dram, System::isTimingMode(), isTimingMode, nextBurstAt, nvm, and QoS::MemCtrl::system().

Referenced by drainResume().

◆ verifyMultiCmd()

Tick MemCtrl::verifyMultiCmd	(	Tick	cmd_tick,
		Tick	max_cmds_per_burst,
		Tick	max_multi_cmd_split = `0`
	)

Check for command bus contention for multi-cycle (2 currently) command.

If there is contention, shift command(s) to next burst. Check verifies that the commands issued per burst is less than a defined max number, maxCommandsPerWindow. Therefore, contention per cycle is not verified and instead is done based on a burst window.

Parameters

cmd_tick	Initial tick of command, to be verified
max_multi_cmd_split	Maximum delay between commands
max_cmds_per_burst	Number of commands that can issue in a burst window

Returns: tick for command issue without contention

Definition at line 710 of file mem_ctrl.cc.

References burstTicks, commandWindow, DPRINTF, and getBurstWindow().

Referenced by DRAMInterface::activateBank(), NVMInterface::chooseRead(), DRAMInterface::doBurstAccess(), and NVMInterface::doBurstAccess().

◆ verifySingleCmd()

Tick MemCtrl::verifySingleCmd	(	Tick	cmd_tick,
		Tick	max_cmds_per_burst
	)

Check for command bus contention for single cycle command.

If there is contention, shift command to next burst. Check verifies that the commands issued per burst is less than a defined max number, maxCommandsPerWindow. Therefore, contention per cycle is not verified and instead is done based on a burst window.

Parameters

cmd_tick	Initial tick of command, to be verified
max_cmds_per_burst	Number of commands that can issue in a burst window

Returns: tick for command issue without contention

Definition at line 687 of file mem_ctrl.cc.

References burstTicks, commandWindow, DPRINTF, and getBurstWindow().

Referenced by DRAMInterface::activateBank(), NVMInterface::chooseRead(), DRAMInterface::doBurstAccess(), NVMInterface::doBurstAccess(), and DRAMInterface::prechargeBank().

◆ writeQueueFull()

bool MemCtrl::writeQueueFull ( unsigned int pkt_count ) const

private

Check if the write queue has room for more entries.

Parameters

pkt_count The number of entries needed in the write queue

Returns: true if write queue is full, false otherwise

Definition at line 170 of file mem_ctrl.cc.

References DPRINTF, QoS::MemCtrl::totalWriteQueueSize, and writeBufferSize.

Referenced by recvTimingReq().

Member Data Documentation

◆ backendLatency

const Tick MemCtrl::backendLatency

private

Pipeline latency of the backend and PHY.

Along with the frontend contribution, this latency is added to reads serviced by the memory.

Definition at line 503 of file mem_ctrl.hh.

Referenced by processRespondEvent().

◆ burstTicks

std::unordered_multiset<Tick> MemCtrl::burstTicks

private

Holds count of commands issued in burst window starting at defined Tick.

This is used to ensure that the command bandwidth does not exceed the allowable media constraints.

Definition at line 459 of file mem_ctrl.hh.

Referenced by pruneBurstTick(), verifyMultiCmd(), and verifySingleCmd().

◆ commandWindow

const Tick MemCtrl::commandWindow

private

Length of a command window, used to check command bandwidth.

Definition at line 509 of file mem_ctrl.hh.

Referenced by getBurstWindow(), verifyMultiCmd(), and verifySingleCmd().

◆ dram

DRAMInterface* const MemCtrl::dram

private

Create pointer to interface of the actual dram media when connected.

Definition at line 464 of file mem_ctrl.hh.

Referenced by accessAndRespond(), addToReadQueue(), addToWriteQueue(), allIntfDrained(), burstAlign(), chooseNextFRFCFS(), doBurstAccess(), drain(), drainResume(), minReadToWriteDataGap(), minWriteToReadDataGap(), packetReady(), processNextReqEvent(), processRespondEvent(), recvAtomic(), recvFunctional(), recvTimingReq(), and startup().

◆ frontendLatency

const Tick MemCtrl::frontendLatency

private

Pipeline latency of the controller frontend.

The frontend contribution is added to writes (that complete when they are in the write buffer) and reads that are serviced the write buffer.

Definition at line 496 of file mem_ctrl.hh.

Referenced by addToReadQueue(), addToWriteQueue(), and processRespondEvent().

◆ isInWriteQueue

std::unordered_set<Addr> MemCtrl::isInWriteQueue

private

To avoid iterating over the write queue to check for overlapping transactions, maintain a set of burst addresses that are currently queued.

Since we merge writes to the same location we never have more than one address to the same burst address.

Definition at line 442 of file mem_ctrl.hh.

Referenced by addToReadQueue(), addToWriteQueue(), and processNextReqEvent().

◆ isTimingMode

bool MemCtrl::isTimingMode

private

Remember if the memory system is in timing mode.

Definition at line 273 of file mem_ctrl.hh.

Referenced by drainResume(), and startup().

◆ memSchedPolicy

Enums::MemSched MemCtrl::memSchedPolicy

private

Memory controller configuration initialized based on parameter values.

Definition at line 489 of file mem_ctrl.hh.

Referenced by chooseNext().

◆ minWritesPerSwitch

const uint32_t MemCtrl::minWritesPerSwitch

private

Definition at line 481 of file mem_ctrl.hh.

Referenced by processNextReqEvent().

◆ nextBurstAt

Tick MemCtrl::nextBurstAt

private

Till when must we wait before issuing next RD/WR burst?

Definition at line 514 of file mem_ctrl.hh.

Referenced by chooseNextFRFCFS(), doBurstAccess(), and startup().

◆ nextReqEvent

EventFunctionWrapper MemCtrl::nextReqEvent

private

Definition at line 288 of file mem_ctrl.hh.

Referenced by addToReadQueue(), addToWriteQueue(), drain(), processNextReqEvent(), requestEventScheduled(), and restartScheduler().

◆ nextReqTime

Tick MemCtrl::nextReqTime

private

The soonest you have to start thinking about the next request is the longest access time that can occur before nextBurstAt.

Assuming you need to precharge, open a new row, and access, it is tRP + tRCD + tCL.

Definition at line 524 of file mem_ctrl.hh.

Referenced by doBurstAccess(), and processNextReqEvent().

◆ nvm

NVMInterface* const MemCtrl::nvm

private

Create pointer to interface of the actual nvm media when connected.

Definition at line 469 of file mem_ctrl.hh.

Referenced by accessAndRespond(), addToReadQueue(), addToWriteQueue(), allIntfDrained(), burstAlign(), chooseNextFRFCFS(), doBurstAccess(), minReadToWriteDataGap(), minWriteToReadDataGap(), packetReady(), processNextReqEvent(), recvAtomic(), recvFunctional(), recvTimingReq(), and startup().

◆ pendingDelete

std::unique_ptr<Packet> MemCtrl::pendingDelete

private

Upstream caches need this packet until true is returned, so hold it for deletion until a subsequent call.

Definition at line 592 of file mem_ctrl.hh.

Referenced by accessAndRespond().

◆ port

MemoryPort MemCtrl::port

private

Our incoming port, for a multi-ported controller add a crossbar in front of it.

Definition at line 268 of file mem_ctrl.hh.

Referenced by accessAndRespond(), getPort(), init(), processNextReqEvent(), and processRespondEvent().

◆ prevArrival

Tick MemCtrl::prevArrival

private

Definition at line 516 of file mem_ctrl.hh.

Referenced by recvTimingReq().

◆ readBufferSize

const uint32_t MemCtrl::readBufferSize

private

The following are basic design parameters of the memory controller, and are initialized based on parameter values.

The rowsPerBank is determined based on the capacity, number of ranks and banks, the burst size, and the row buffer size.

Definition at line 477 of file mem_ctrl.hh.

Referenced by readQueueFull().

◆ readQueue

std::vector<MemPacketQueue> MemCtrl::readQueue

private

The controller's main read and write queues, with support for QoS reordering.

Definition at line 432 of file mem_ctrl.hh.

Referenced by addToReadQueue(), printQs(), processNextReqEvent(), recvTimingReq(), and selQueue().

◆ readsThisTime

uint32_t MemCtrl::readsThisTime

private

Definition at line 483 of file mem_ctrl.hh.

Referenced by doBurstAccess(), and processNextReqEvent().

◆ respondEvent

EventFunctionWrapper MemCtrl::respondEvent

private

Definition at line 291 of file mem_ctrl.hh.

Referenced by processNextReqEvent(), processRespondEvent(), and respondEventScheduled().

◆ respQueue

std::deque<MemPacket*> MemCtrl::respQueue

private

Response queue where read packets wait after we're done working with them, but it's not time to send the response yet.

The responses are stored separately mostly to keep the code clean and help with events scheduling. For all logical purposes such as sizing the read queue, this and the main read queue need to be added together.

Definition at line 452 of file mem_ctrl.hh.

Referenced by addToReadQueue(), drain(), printQs(), processNextReqEvent(), processRespondEvent(), and readQueueFull().

◆ retryRdReq

bool MemCtrl::retryRdReq

private

Remember if we have to retry a request when available.

Definition at line 278 of file mem_ctrl.hh.

Referenced by processRespondEvent(), and recvTimingReq().

◆ retryWrReq

bool MemCtrl::retryWrReq

private

Definition at line 279 of file mem_ctrl.hh.

Referenced by processNextReqEvent(), and recvTimingReq().

◆ stats

CtrlStats MemCtrl::stats

private

Definition at line 586 of file mem_ctrl.hh.

Referenced by addToReadQueue(), addToWriteQueue(), doBurstAccess(), processNextReqEvent(), and recvTimingReq().

◆ writeBufferSize

const uint32_t MemCtrl::writeBufferSize

private

Definition at line 478 of file mem_ctrl.hh.

Referenced by addToWriteQueue(), processNextReqEvent(), and writeQueueFull().

◆ writeHighThreshold

const uint32_t MemCtrl::writeHighThreshold

private

Definition at line 479 of file mem_ctrl.hh.

Referenced by processNextReqEvent().

◆ writeLowThreshold

const uint32_t MemCtrl::writeLowThreshold

private

Definition at line 480 of file mem_ctrl.hh.

Referenced by processNextReqEvent().

◆ writeQueue

std::vector<MemPacketQueue> MemCtrl::writeQueue

private

Definition at line 433 of file mem_ctrl.hh.

Referenced by addToReadQueue(), addToWriteQueue(), printQs(), processNextReqEvent(), recvTimingReq(), and selQueue().

◆ writesThisTime

uint32_t MemCtrl::writesThisTime

private

Definition at line 482 of file mem_ctrl.hh.

Referenced by doBurstAccess(), and processNextReqEvent().

The documentation for this class was generated from the following files:

mem/mem_ctrl.hh
mem/mem_ctrl.cc

Classes

Public Member Functions

Protected Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ MemCtrl()

Member Function Documentation

◆ accessAndRespond()

◆ addToReadQueue()

◆ addToWriteQueue()

◆ allIntfDrained()

◆ burstAlign()

◆ chooseNext()

◆ chooseNextFRFCFS()

◆ doBurstAccess()

◆ drain()

◆ drainResume()

◆ getBurstWindow()

◆ getPort()

◆ init()

◆ inReadBusState()

◆ inWriteBusState()

◆ minReadToWriteDataGap()

◆ minWriteToReadDataGap()

◆ packetReady()

◆ printQs()

◆ processNextReqEvent()

◆ processRespondEvent()

◆ pruneBurstTick()

◆ readQueueFull()

◆ recvAtomic()

◆ recvFunctional()

◆ recvTimingReq()

◆ requestEventScheduled()

◆ respondEventScheduled()

◆ restartScheduler()

◆ selQueue()

◆ startup()

◆ verifyMultiCmd()

◆ verifySingleCmd()

◆ writeQueueFull()

Member Data Documentation

◆ backendLatency

◆ burstTicks

◆ commandWindow

◆ dram

◆ frontendLatency

◆ isInWriteQueue

◆ isTimingMode

◆ memSchedPolicy

◆ minWritesPerSwitch

◆ nextBurstAt

◆ nextReqEvent

◆ nextReqTime

◆ nvm

◆ pendingDelete

◆ port

◆ prevArrival

◆ readBufferSize

◆ readQueue

◆ readsThisTime

◆ respondEvent

◆ respQueue

◆ retryRdReq

◆ retryWrReq

◆ stats

◆ writeBufferSize

◆ writeHighThreshold

◆ writeLowThreshold

◆ writeQueue

◆ writesThisTime