#include <signature_path_v2.hh>

Inheritance diagram for gem5::prefetch::SignaturePathV2:

Classes
struct	GlobalHistoryEntry
	Global History Register entry datatype. More...

Public Member Functions
	SignaturePathV2 (const SignaturePathPrefetcherV2Params &p)

	~SignaturePathV2 ()=default

Public Member Functions inherited from gem5::prefetch::SignaturePath
	SignaturePath (const SignaturePathPrefetcherParams &p)

	~SignaturePath ()=default

void	calculatePrefetch (const PrefetchInfo &pfi, std::vector< AddrPriority > &addresses, const CacheAccessor &cache) override

Public Member Functions inherited from gem5::prefetch::Queued
	Queued (const QueuedPrefetcherParams &p)

virtual	~Queued ()

void	notify (const CacheAccessProbeArg &acc, const PrefetchInfo &pfi) override
	Notify prefetcher of cache access (may be any access or just misses, depending on cache parameters.)

void	insert (const PacketPtr &pkt, PrefetchInfo &new_pfi, int32_t priority, const CacheAccessor &cache)

PacketPtr	getPacket () override

Tick	nextPrefetchReadyTime () const override

void	printQueue (const std::list< DeferredPacket > &queue) const

Public Member Functions inherited from gem5::prefetch::Base
	Base (const BasePrefetcherParams &p)

virtual	~Base ()=default

virtual void	setParentInfo (System sys, ProbeManager pm, unsigned blk_size)

virtual void	notifyFill (const CacheAccessProbeArg &acc)
	Notify prefetcher of cache fill.

virtual void	notifyEvict (const EvictionInfo &info)
	Notify prefetcher of cache eviction.

void	prefetchUnused ()

void	incrDemandMhsrMisses ()

void	pfHitInCache ()

void	pfHitInMSHR ()

void	pfHitInWB ()

void	regProbeListeners () override
	Register probe points for this object.

void	probeNotify (const CacheAccessProbeArg &acc, bool miss)
	Process a notification event from the ProbeListener.

void	addEventProbe (SimObject obj, const char name)
	Add a SimObject and a probe name to listen events from.

void	addMMU (BaseMMU *mmu)
	Add a BaseMMU object to be used whenever a translation is needed.

Public Member Functions inherited from gem5::ClockedObject
	ClockedObject (const ClockedObjectParams &p)

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

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

Public Member Functions inherited from gem5::SimObject
const Params &	params () const

	SimObject (const Params &p)

virtual	~SimObject ()

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

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

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

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

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

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

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

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

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

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

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

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

Public Member Functions inherited from gem5::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.

void	setCurTick (Tick newVal)

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

	EventManager (EventManager *em)

	EventManager (EventQueue *eq)

Public Member Functions inherited from gem5::Serializable
	Serializable ()

virtual	~Serializable ()

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

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

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

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

Public Member Functions inherited from gem5::Drainable
DrainState	drainState () const
	Return the current drain state of an object.

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

Public Member Functions inherited from gem5::statistics::Group
	Group (Group parent, const char name=nullptr)
	Construct a new statistics group.

virtual	~Group ()

virtual void	regStats ()
	Callback to set stat parameters.

virtual void	resetStats ()
	Callback to reset stats.

virtual void	preDumpStats ()
	Callback before stats are dumped.

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

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

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

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

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

void	mergeStatGroup (Group *block)
	Merge the contents (stats & children) of a block to this block.

	Group ()=delete

	Group (const Group &)=delete

Group &	operator= (const Group &)=delete

Public Member Functions inherited from gem5::Named
	Named (const std::string &name_)

virtual	~Named ()=default

virtual std::string	name () const

Public Member Functions inherited from gem5::Clocked
void	updateClockPeriod ()
	Update the tick to the current tick.

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.

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

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.

uint64_t	frequency () const

Tick	clockPeriod () const

double	voltage () const

Cycles	ticksToCycles (Tick t) const

Tick	cyclesToTicks (Cycles c) const

Private Member Functions
double	calculateLookaheadConfidence (PatternEntry const &sig, PatternStrideEntry const &lookahead) const override
	Computes the lookahead path confidence of the provided pattern entry.

double	calculatePrefetchConfidence (PatternEntry const &sig, PatternStrideEntry const &lookahead) const override
	Computes the prefetch confidence of the provided pattern entry.

void	increasePatternEntryCounter (PatternEntry &pattern_entry, PatternStrideEntry &pstride_entry) override
	Increases the counter of a given PatternEntry/PatternStrideEntry.

void	handleSignatureTableMiss (stride_t current_block, signature_t &new_signature, double &new_conf, stride_t &new_stride) override
	Whenever a new SignatureEntry is allocated, it computes the new signature to be used with the new entry, the resulting stride and the initial path confidence of the new entry.

void	auxiliaryPrefetcher (Addr ppn, stride_t current_block, bool is_secure, std::vector< AddrPriority > &addresses) override
	In this version of the Signature Path Prefetcher, there is no auxiliary prefetcher, so this function does not perform any actions.

virtual void	handlePageCrossingLookahead (signature_t signature, stride_t last_offset, stride_t delta, double path_confidence) override
	Handles the situation when the lookahead process has crossed the boundaries of the current page.

Private Attributes
AssociativeCache< GlobalHistoryEntry >	globalHistoryRegister
	Global History Register.

Additional Inherited Members
Public Types inherited from gem5::prefetch::Queued
using	AddrPriority = std::pair<Addr, int32_t>

Public Types inherited from gem5::ClockedObject
using	Params = ClockedObjectParams
	Parameters of ClockedObject.

Public Types inherited from gem5::SimObject
typedef SimObjectParams	Params

Static Public Member Functions inherited from gem5::SimObject
static void	serializeAll (const std::string &cpt_dir)
	Create a checkpoint by serializing all SimObjects in the system.

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

static void	setSimObjectResolver (SimObjectResolver *resolver)
	There is a single object name resolver, and it is only set when simulation is restoring from checkpoints.

static SimObjectResolver *	getSimObjectResolver ()
	There is a single object name resolver, and it is only set when simulation is restoring from checkpoints.

Static Public Member Functions inherited from gem5::Serializable
static const std::string &	currentSection ()
	Gets the fully-qualified name of the active section.

static void	generateCheckpointOut (const std::string &cpt_dir, std::ofstream &outstream)
	Generate a checkpoint file so that the serialization can be routed to it.

Public Attributes inherited from gem5::ClockedObject
PowerState *	powerState

Protected Types inherited from gem5::prefetch::SignaturePath
typedef uint16_t	signature_t
	Signature type.

typedef int16_t	stride_t
	Stride type.

Protected Types inherited from gem5::prefetch::Queued
using	const_iterator = std::list<DeferredPacket>::const_iterator

using	iterator = std::list<DeferredPacket>::iterator

Protected Member Functions inherited from gem5::prefetch::SignaturePath
signature_t	updateSignature (signature_t sig, stride_t str) const
	Generates a new signature from an existing one and a new stride.

void	addPrefetch (Addr ppn, stride_t last_block, stride_t delta, double path_confidence, signature_t signature, bool is_secure, std::vector< AddrPriority > &addresses)
	Generates an address to be prefetched.

SignatureEntry &	getSignatureEntry (Addr ppn, bool is_secure, stride_t block, bool &miss, stride_t &stride, double &initial_confidence)
	Obtains the SignatureEntry of the given page, if the page is not found, it allocates a new one, replacing an existing entry if needed It also provides the stride of the current block and the initial path confidence of the corresponding entry.

PatternEntry &	getPatternEntry (Addr signature)
	Obtains the PatternEntry of the given signature, if the signature is not found, it allocates a new one, replacing an existing entry if needed.

void	updatePatternTable (Addr signature, stride_t stride)
	Updates the pattern table with the provided signature and stride.

Protected Member Functions inherited from gem5::prefetch::Base
bool	observeAccess (const PacketPtr &pkt, bool miss, bool prefetched) const
	Determine if this access should be observed.

bool	samePage (Addr a, Addr b) const
	Determine if addresses are on the same page.

Addr	blockAddress (Addr a) const
	Determine the address of the block in which a lays.

Addr	blockIndex (Addr a) const
	Determine the address of a at block granularity.

Addr	pageAddress (Addr a) const
	Determine the address of the page in which a lays.

Addr	pageOffset (Addr a) const
	Determine the page-offset of a

Addr	pageIthBlockAddress (Addr page, uint32_t i) const
	Build the address of the i-th block inside the page.

Protected Member Functions inherited from gem5::Drainable
	Drainable ()

virtual	~Drainable ()

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

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

Protected Member Functions inherited from gem5::Clocked
	Clocked (ClockDomain &clk_domain)
	Create a clocked object and set the clock domain based on the parameters.

	Clocked (Clocked &)=delete

Clocked &	operator= (Clocked &)=delete

virtual	~Clocked ()
	Virtual destructor due to inheritance.

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

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

Protected Attributes inherited from gem5::prefetch::SignaturePath
const unsigned	stridesPerPatternEntry
	Number of strides stored in each pattern entry.

const uint8_t	signatureShift
	Number of bits to shift when generating a new signature.

const signature_t	signatureBits
	Size of the signature, in bits.

const double	prefetchConfidenceThreshold
	Minimum confidence to issue a prefetch.

const double	lookaheadConfidenceThreshold
	Minimum confidence to keep navigating lookahead entries.

AssociativeSet< SignatureEntry >	signatureTable
	Signature table.

AssociativeCache< PatternEntry >	patternTable
	Pattern table.

Protected Attributes inherited from gem5::prefetch::Queued
std::list< DeferredPacket >	pfq

std::list< DeferredPacket >	pfqMissingTranslation

const unsigned	queueSize
	Maximum size of the prefetch queue.

const unsigned	missingTranslationQueueSize
	Maximum size of the queue holding prefetch requests with missing address translations.

const Cycles	latency
	Cycles after generation when a prefetch can first be issued.

const bool	queueSquash
	Squash queued prefetch if demand access observed.

const bool	queueFilter
	Filter prefetches if already queued.

const bool	cacheSnoop
	Snoop the cache before generating prefetch (cheating basically)

const bool	tagPrefetch
	Tag prefetch with PC of generating access?

const unsigned int	throttleControlPct
	Percentage of requests that can be throttled.

gem5::prefetch::Queued::QueuedStats	statsQueued

Protected Attributes inherited from gem5::prefetch::Base
System *	system
	Pointer to the parent system.

ProbeManager *	probeManager
	Pointer to the parent cache's probe manager.

unsigned	blkSize
	The block size of the parent cache.

unsigned	lBlkSize
	log_2(block size of the parent cache).

const bool	onMiss
	Only consult prefetcher on cache misses?

const bool	onRead
	Consult prefetcher on reads?

const bool	onWrite
	Consult prefetcher on reads?

const bool	onData
	Consult prefetcher on data accesses?

const bool	onInst
	Consult prefetcher on instruction accesses?

const RequestorID	requestorId
	Request id for prefetches.

const Addr	pageBytes

const bool	prefetchOnAccess
	Prefetch on every access, not just misses.

const bool	prefetchOnPfHit
	Prefetch on hit on prefetched lines.

const bool	useVirtualAddresses
	Use Virtual Addresses for prefetching.

gem5::prefetch::Base::StatGroup	prefetchStats

uint64_t	issuedPrefetches
	Total prefetches issued.

uint64_t	usefulPrefetches
	Total prefetches that has been useful.

BaseMMU *	mmu
	Registered mmu for address translations.

Protected Attributes inherited from gem5::SimObject
const SimObjectParams &	_params
	Cached copy of the object parameters.

Protected Attributes inherited from gem5::EventManager
EventQueue *	eventq
	A pointer to this object's event queue.

Detailed Description

Definition at line 56 of file signature_path_v2.hh.

Constructor & Destructor Documentation

◆ SignaturePathV2()

gem5::prefetch::SignaturePathV2::SignaturePathV2 ( const SignaturePathPrefetcherV2Params & p )

Definition at line 43 of file signature_path_v2.cc.

◆ ~SignaturePathV2()

gem5::prefetch::SignaturePathV2::~SignaturePathV2 ( )

default

Member Function Documentation

◆ auxiliaryPrefetcher()

void gem5::prefetch::SignaturePathV2::auxiliaryPrefetcher	(	Addr	ppn,
		stride_t	current_block,
		bool	is_secure,
		std::vector< AddrPriority > &	addresses )

inlineoverrideprivatevirtual

In this version of the Signature Path Prefetcher, there is no auxiliary prefetcher, so this function does not perform any actions.

Reimplemented from gem5::prefetch::SignaturePath.

Definition at line 88 of file signature_path_v2.hh.

◆ calculateLookaheadConfidence()

double gem5::prefetch::SignaturePathV2::calculateLookaheadConfidence	(	PatternEntry const &	sig,
		PatternStrideEntry const &	lookahead ) const

overrideprivatevirtual

Computes the lookahead path confidence of the provided pattern entry.

Parameters

sig	the PatternEntry to use
lookahead	PatternStrideEntry within the provided PatternEntry

Returns: the computed confidence factor

maximum confidence is 0.95, guaranteeing that current confidence will eventually fall beyond the threshold

Reimplemented from gem5::prefetch::SignaturePath.

Definition at line 83 of file signature_path_v2.cc.

References gem5::prefetch::SignaturePath::PatternEntry::counter, gem5::prefetch::SignaturePath::PatternStrideEntry::counter, gem5::prefetch::Base::issuedPrefetches, and gem5::prefetch::Base::usefulPrefetches.

◆ calculatePrefetchConfidence()

double gem5::prefetch::SignaturePathV2::calculatePrefetchConfidence	(	PatternEntry const &	sig,
		PatternStrideEntry const &	entry ) const

overrideprivatevirtual

Computes the prefetch confidence of the provided pattern entry.

Parameters

sig	the PatternEntry to use
entry	PatternStrideEntry within the provided PatternEntry

Returns: the computed confidence factor

Reimplemented from gem5::prefetch::SignaturePath.

Definition at line 92 of file signature_path_v2.cc.

References gem5::prefetch::SignaturePath::PatternEntry::counter, and gem5::prefetch::SignaturePath::PatternStrideEntry::counter.

◆ handlePageCrossingLookahead()

void gem5::prefetch::SignaturePathV2::handlePageCrossingLookahead	(	signature_t	signature,
		stride_t	last_offset,
		stride_t	delta,
		double	path_confidence )

overrideprivatevirtual

Handles the situation when the lookahead process has crossed the boundaries of the current page.

This is not fully described in the paper that was used to implement this code, however, the article describing the upgraded version of this prefetcher provides some details. For this prefetcher, there are no specific actions to be done.

Parameters

signature	the lookahead signature that crossed the page
delta	the current stride that caused it
last_offset	the last accessed block within the page
path_confidence	the path confidence at the moment of crossing

Reimplemented from gem5::prefetch::SignaturePath.

Definition at line 120 of file signature_path_v2.cc.

References gem5::prefetch::SignaturePathV2::GlobalHistoryEntry::confidence, gem5::prefetch::SignaturePathV2::GlobalHistoryEntry::delta, globalHistoryRegister, gem5::prefetch::SignaturePathV2::GlobalHistoryEntry::lastBlock, and gem5::prefetch::SignaturePathV2::GlobalHistoryEntry::signature.

◆ handleSignatureTableMiss()

void gem5::prefetch::SignaturePathV2::handleSignatureTableMiss	(	stride_t	current_block,
		signature_t &	new_signature,
		double &	new_conf,
		stride_t &	new_stride )

overrideprivatevirtual

Whenever a new SignatureEntry is allocated, it computes the new signature to be used with the new entry, the resulting stride and the initial path confidence of the new entry.

Parameters

current_block	accessed block within the page of the associated entry
new_signature	new signature of the allocated entry
new_conf	the initial path confidence of this entry
new_stride	the resulting current stride

Reimplemented from gem5::prefetch::SignaturePath.

Definition at line 55 of file signature_path_v2.cc.

References globalHistoryRegister.