gem5  v20.1.0.0
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Prefetcher::SignaturePathV2 Class Reference

#include <signature_path_v2.hh>

Inheritance diagram for Prefetcher::SignaturePathV2:
Prefetcher::SignaturePath Prefetcher::Queued Prefetcher::Base ClockedObject SimObject Clocked EventManager Serializable Drainable Stats::Group

Classes

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

Public Member Functions

 SignaturePathV2 (const SignaturePathPrefetcherV2Params *p)
 
 ~SignaturePathV2 ()=default
 
- Public Member Functions inherited from Prefetcher::SignaturePath
 SignaturePath (const SignaturePathPrefetcherParams *p)
 
 ~SignaturePath ()=default
 
void calculatePrefetch (const PrefetchInfo &pfi, std::vector< AddrPriority > &addresses) override
 
- Public Member Functions inherited from Prefetcher::Queued
 Queued (const QueuedPrefetcherParams *p)
 
virtual ~Queued ()
 
void notify (const PacketPtr &pkt, const PrefetchInfo &pfi) override
 Notify prefetcher of cache access (may be any access or just misses, depending on cache parameters.) More...
 
void insert (const PacketPtr &pkt, PrefetchInfo &new_pfi, int32_t priority)
 
PacketPtr getPacket () override
 
Tick nextPrefetchReadyTime () const override
 
- Public Member Functions inherited from Prefetcher::Base
 Base (const BasePrefetcherParams *p)
 
virtual ~Base ()=default
 
virtual void setCache (BaseCache *_cache)
 
virtual void notifyFill (const PacketPtr &pkt)
 Notify prefetcher of cache fill. More...
 
void regProbeListeners () override
 Register probe points for this object. More...
 
void probeNotify (const PacketPtr &pkt, bool miss)
 Process a notification event from the ProbeListener. More...
 
void addEventProbe (SimObject *obj, const char *name)
 Add a SimObject and a probe name to listen events from. More...
 
void addTLB (BaseTLB *tlb)
 Add a BaseTLB object to be used whenever a translation is needed. More...
 
- Public Member Functions inherited from ClockedObject
 ClockedObject (const ClockedObjectParams *p)
 
const Paramsparams () 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 Paramsparams () const
 
 SimObject (const Params *_params)
 
virtual ~SimObject ()
 
virtual const std::string name () const
 
virtual void init ()
 init() is called after all C++ SimObjects have been created and all ports are connected. More...
 
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...
 
ProbeManagergetProbeManager ()
 Get the probe manager for this object. More...
 
virtual PortgetPort (const std::string &if_name, PortID idx=InvalidPortID)
 Get a port with a given name and index. More...
 
virtual void startup ()
 startup() is the final initialization call before simulation. 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
EventQueueeventQueue () 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 InforesolveStat (std::string name) const
 Resolve a stat by its name within this group. More...
 
 Group ()=delete
 
 Group (const Group &)=delete
 
Groupoperator= (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
 

Private Member Functions

double calculateLookaheadConfidence (PatternEntry const &sig, PatternStrideEntry const &lookahead) const override
 Computes the lookahead path confidence of the provided pattern entry. More...
 
double calculatePrefetchConfidence (PatternEntry const &sig, PatternStrideEntry const &lookahead) const override
 Computes the prefetch confidence of the provided pattern entry. More...
 
void increasePatternEntryCounter (PatternEntry &pattern_entry, PatternStrideEntry &pstride_entry) override
 Increases the counter of a given PatternEntry/PatternStrideEntry. More...
 
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. More...
 
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. More...
 
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. More...
 

Private Attributes

AssociativeSet< GlobalHistoryEntryglobalHistoryRegister
 Global History Register. More...
 

Additional Inherited Members

- Public Types inherited from Prefetcher::Queued
using AddrPriority = std::pair< Addr, int32_t >
 
- 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 SimObjectfind (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
PowerStatepowerState
 
- Protected Types inherited from Prefetcher::SignaturePath
typedef uint16_t signature_t
 Signature type. More...
 
typedef int16_t stride_t
 Stride type. More...
 
- Protected Types inherited from Prefetcher::Queued
using const_iterator = std::list< DeferredPacket >::const_iterator
 
using iterator = std::list< DeferredPacket >::iterator
 
- Protected Member Functions inherited from Prefetcher::SignaturePath
signature_t updateSignature (signature_t sig, stride_t str) const
 Generates a new signature from an existing one and a new stride. More...
 
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. More...
 
SignatureEntrygetSignatureEntry (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. More...
 
PatternEntrygetPatternEntry (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. More...
 
void updatePatternTable (Addr signature, stride_t stride)
 Updates the pattern table with the provided signature and stride. More...
 
- Protected Member Functions inherited from Prefetcher::Base
bool observeAccess (const PacketPtr &pkt, bool miss) const
 Determine if this access should be observed. More...
 
bool inCache (Addr addr, bool is_secure) const
 Determine if address is in cache. More...
 
bool inMissQueue (Addr addr, bool is_secure) const
 Determine if address is in cache miss queue. More...
 
bool hasBeenPrefetched (Addr addr, bool is_secure) const
 
bool samePage (Addr a, Addr b) const
 Determine if addresses are on the same page. More...
 
Addr blockAddress (Addr a) const
 Determine the address of the block in which a lays. More...
 
Addr blockIndex (Addr a) const
 Determine the address of a at block granularity. More...
 
Addr pageAddress (Addr a) const
 Determine the address of the page in which a lays. More...
 
Addr pageOffset (Addr a) const
 Determine the page-offset of a
More...
 
Addr pageIthBlockAddress (Addr page, uint32_t i) const
 Build the address of the i-th block inside the page. More...
 
- Protected Member Functions inherited from Drainable
 Drainable ()
 
virtual ~Drainable ()
 
virtual void drainResume ()
 Resume execution after a successful drain. More...
 
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
 
Clockedoperator= (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...
 
- Protected Attributes inherited from Prefetcher::SignaturePath
const unsigned stridesPerPatternEntry
 Number of strides stored in each pattern entry. More...
 
const uint8_t signatureShift
 Number of bits to shift when generating a new signature. More...
 
const signature_t signatureBits
 Size of the signature, in bits. More...
 
const double prefetchConfidenceThreshold
 Minimum confidence to issue a prefetch. More...
 
const double lookaheadConfidenceThreshold
 Minimum confidence to keep navigating lookahead entries. More...
 
AssociativeSet< SignatureEntrysignatureTable
 Signature table. More...
 
AssociativeSet< PatternEntrypatternTable
 Pattern table. More...
 
- Protected Attributes inherited from Prefetcher::Queued
std::list< DeferredPacketpfq
 
std::list< DeferredPacketpfqMissingTranslation
 
const unsigned queueSize
 Maximum size of the prefetch queue. More...
 
const unsigned missingTranslationQueueSize
 Maximum size of the queue holding prefetch requests with missing address translations. More...
 
const Cycles latency
 Cycles after generation when a prefetch can first be issued. More...
 
const bool queueSquash
 Squash queued prefetch if demand access observed. More...
 
const bool queueFilter
 Filter prefetches if already queued. More...
 
const bool cacheSnoop
 Snoop the cache before generating prefetch (cheating basically) More...
 
const bool tagPrefetch
 Tag prefetch with PC of generating access? More...
 
const unsigned int throttleControlPct
 Percentage of requests that can be throttled. More...
 
Prefetcher::Queued::QueuedStats statsQueued
 
- Protected Attributes inherited from Prefetcher::Base
BaseCachecache
 Pointr to the parent cache. More...
 
unsigned blkSize
 The block size of the parent cache. More...
 
unsigned lBlkSize
 log_2(block size of the parent cache). More...
 
const bool onMiss
 Only consult prefetcher on cache misses? More...
 
const bool onRead
 Consult prefetcher on reads? More...
 
const bool onWrite
 Consult prefetcher on reads? More...
 
const bool onData
 Consult prefetcher on data accesses? More...
 
const bool onInst
 Consult prefetcher on instruction accesses? More...
 
const RequestorID requestorId
 Request id for prefetches. More...
 
const Addr pageBytes
 
const bool prefetchOnAccess
 Prefetch on every access, not just misses. More...
 
const bool useVirtualAddresses
 Use Virtual Addresses for prefetching. More...
 
Prefetcher::Base::StatGroup prefetchStats
 
uint64_t issuedPrefetches
 Total prefetches issued. More...
 
uint64_t usefulPrefetches
 Total prefetches that has been useful. More...
 
BaseTLBtlb
 Registered tlb for address translations. More...
 
- Protected Attributes inherited from SimObject
const SimObjectParams * _params
 Cached copy of the object parameters. More...
 
- Protected Attributes inherited from EventManager
EventQueueeventq
 A pointer to this object's event queue. More...
 

Detailed Description

Definition at line 52 of file signature_path_v2.hh.

Constructor & Destructor Documentation

◆ SignaturePathV2()

Prefetcher::SignaturePathV2::SignaturePathV2 ( const SignaturePathPrefetcherV2Params *  p)

Definition at line 39 of file signature_path_v2.cc.

◆ ~SignaturePathV2()

Prefetcher::SignaturePathV2::~SignaturePathV2 ( )
default

Member Function Documentation

◆ auxiliaryPrefetcher()

void Prefetcher::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 Prefetcher::SignaturePath.

Definition at line 84 of file signature_path_v2.hh.

◆ calculateLookaheadConfidence()

double Prefetcher::SignaturePathV2::calculateLookaheadConfidence ( PatternEntry const &  sig,
PatternStrideEntry const &  lookahead 
) const
overrideprivatevirtual

Computes the lookahead path confidence of the provided pattern entry.

Parameters
sigthe PatternEntry to use
lookaheadPatternStrideEntry 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 Prefetcher::SignaturePath.

Definition at line 78 of file signature_path_v2.cc.

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

◆ calculatePrefetchConfidence()

double Prefetcher::SignaturePathV2::calculatePrefetchConfidence ( PatternEntry const &  sig,
PatternStrideEntry const &  entry 
) const
overrideprivatevirtual

Computes the prefetch confidence of the provided pattern entry.

Parameters
sigthe PatternEntry to use
entryPatternStrideEntry within the provided PatternEntry
Returns
the computed confidence factor

Reimplemented from Prefetcher::SignaturePath.

Definition at line 87 of file signature_path_v2.cc.

References Prefetcher::SignaturePath::PatternStrideEntry::counter, and Prefetcher::SignaturePath::PatternEntry::counter.

◆ handlePageCrossingLookahead()

void Prefetcher::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
signaturethe lookahead signature that crossed the page
deltathe current stride that caused it
last_offsetthe last accessed block within the page
path_confidencethe path confidence at the moment of crossing

Reimplemented from Prefetcher::SignaturePath.

Definition at line 115 of file signature_path_v2.cc.

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

◆ handleSignatureTableMiss()

void Prefetcher::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_blockaccessed block within the page of the associated entry
new_signaturenew signature of the allocated entry
new_confthe initial path confidence of this entry
new_stridethe resulting current stride

Reimplemented from Prefetcher::SignaturePath.

Definition at line 50 of file signature_path_v2.cc.

References globalHistoryRegister.

◆ increasePatternEntryCounter()

void Prefetcher::SignaturePathV2::increasePatternEntryCounter ( PatternEntry pattern_entry,
PatternStrideEntry pstride_entry 
)
overrideprivatevirtual

Increases the counter of a given PatternEntry/PatternStrideEntry.

Parameters
pattern_entrythe corresponding PatternEntry
pstride_entrythe PatternStrideEntry within the PatternEntry

Reimplemented from Prefetcher::SignaturePath.

Definition at line 95 of file signature_path_v2.cc.

References Prefetcher::SignaturePath::PatternStrideEntry::counter, Prefetcher::SignaturePath::PatternEntry::counter, SatCounter::counter, SatCounter::isSaturated(), and Prefetcher::SignaturePath::PatternEntry::strideEntries.

Member Data Documentation

◆ globalHistoryRegister

AssociativeSet<GlobalHistoryEntry> Prefetcher::SignaturePathV2::globalHistoryRegister
private

Global History Register.

Definition at line 65 of file signature_path_v2.hh.

Referenced by handlePageCrossingLookahead(), and handleSignatureTableMiss().


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

Generated on Wed Sep 30 2020 14:03:07 for gem5 by doxygen 1.8.17