A pattern that checks whether the difference of the value and the dictionary entries' is below a certain threshold. More...

#include <dictionary_compressor.hh>

Inheritance diagram for gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >:

Public Types
typedef BaseDictionaryCompressorParams	Params

Public Types inherited from gem5::compression::BaseDictionaryCompressor
typedef BaseDictionaryCompressorParams	Params

Public Types inherited from gem5::compression::Base
typedef BaseCacheCompressorParams	Params

Public Types inherited from gem5::SimObject
typedef SimObjectParams	Params

Public Types inherited from gem5::compression::DictionaryCompressor< T >::Pattern
typedef BaseDictionaryCompressorParams	Params

Public Member Functions
	DeltaPattern (const int number, const uint64_t code, const uint64_t metadata_length, const int match_location, const DictionaryEntry bytes)

DictionaryEntry	decompress (const DictionaryEntry dict_bytes) const override
	Decompress the pattern.

	DictionaryCompressor (const Params &p)

	~DictionaryCompressor ()=default

Public Member Functions inherited from gem5::compression::BaseDictionaryCompressor
	BaseDictionaryCompressor (const Params &p)

	~BaseDictionaryCompressor ()=default

Public Member Functions inherited from gem5::compression::Base
	Base (const Params &p)

virtual	~Base ()=default

virtual void	setCache (BaseCache *_cache)
	The cache can only be set once.

std::unique_ptr< CompressionData >	compress (const uint64_t *data, Cycles &comp_lat, Cycles &decomp_lat)
	Apply the compression process to the cache line.

Cycles	getDecompressionLatency (const CacheBlk *blk)
	Get the decompression latency if the block is compressed.

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.

virtual void	regProbeListeners ()
	Register probe listeners 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 (std::string_view name_)

virtual	~Named ()=default

virtual std::string	name () const

Public Member Functions inherited from gem5::compression::DictionaryCompressor< T >::Pattern
	Pattern (const int number, const uint64_t code, const uint64_t metadata_length, const uint64_t num_unmatched_bits, const int match_location, const bool allocate=true)
	Default constructor.

virtual	~Pattern ()=default
	Default destructor.

int	getPatternNumber () const
	Get enum number associated to this pattern.

uint8_t	getCode () const
	Get code of this pattern.

uint8_t	getMatchLocation () const
	Get the index of the dictionary match location.

virtual std::size_t	getSizeBits () const
	Get size, in bits, of the pattern (excluding prefix).

bool	shouldAllocate () const
	Determine if pattern allocates a dictionary entry.

std::string	print () const
	Extract pattern's information to a string.

	DictionaryCompressor (const Params &p)

	~DictionaryCompressor ()=default

Static Public Member Functions
static bool	isValidDelta (const DictionaryEntry &bytes, const DictionaryEntry &base_bytes)
	Compares a given value against a base to calculate their delta, and then determines whether it fits a limited sized container.

static bool	isPattern (const DictionaryEntry &bytes, const DictionaryEntry &dict_bytes, const int match_location)

Static Public Member Functions inherited from gem5::compression::Base
static void	setDecompressionLatency (CacheBlk *blk, const Cycles lat)
	Set the decompression latency of compressed block.

static void	setSizeBits (CacheBlk *blk, const std::size_t size_bits)
	Set the size of the compressed block, in bits.

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.

Protected Types
typedef std::array< uint8_t, sizeof(T)>	DictionaryEntry
	Convenience typedef for a dictionary entry.

Protected Types inherited from gem5::compression::Base
typedef uint64_t	Chunk
	A chunk is a basic lexical unit.

Protected Types inherited from gem5::compression::DictionaryCompressor< T >::Pattern
typedef std::array< uint8_t, sizeof(T)>	DictionaryEntry
	Convenience typedef for a dictionary entry.

Protected Member Functions
virtual std::unique_ptr< Pattern >	getPattern (const DictionaryEntry &bytes, const DictionaryEntry &dict_bytes, const int match_location) const=0
	Since the factory cannot be instantiated here, classes that inherit from this base class have to implement the call to their factory's getPattern.

std::unique_ptr< Pattern >	compressValue (const T data)
	Compress data.

T	decompressValue (const Pattern *pattern)
	Decompress a pattern into a value that fits in a dictionary entry.

virtual void	resetDictionary ()
	Clear all dictionary entries.

virtual void	addToDictionary (const DictionaryEntry data)=0
	Add an entry to the dictionary.

virtual std::unique_ptr< DictionaryCompressor::CompData >	instantiateDictionaryCompData () const
	Instantiate a compression data of the sub-class compressor.

std::unique_ptr< Base::CompressionData >	compress (const std::vector< Chunk > &chunks)
	Apply compression.

std::unique_ptr< Base::CompressionData >	compress (const std::vector< Chunk > &chunks, Cycles &comp_lat, Cycles &decomp_lat) override
	Apply the compression process to the cache line.

void	decompress (const CompressionData comp_data, uint64_t data) override
	Apply the decompression process to the compressed data.

Protected Member Functions inherited from gem5::compression::BaseDictionaryCompressor
virtual uint64_t	getNumPatterns () const =0
	Trick function to get the number of patterns.

virtual std::string	getName (int number) const =0
	Get meta-name assigned to the given pattern.

Protected Member Functions inherited from gem5::compression::Base
std::vector< Chunk >	toChunks (const uint64_t *data) const
	This function splits the raw data into chunks, so that it can be parsed by the compressor.

void	fromChunks (const std::vector< Chunk > &chunks, uint64_t *data) const
	This function re-joins the chunks to recreate the original data.

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::compression::DictionaryCompressor< T >::Pattern
std::unique_ptr< Pattern >	compressValue (const T data)
	Compress data.

T	decompressValue (const Pattern *pattern)
	Decompress a pattern into a value that fits in a dictionary entry.

std::unique_ptr< Base::CompressionData >	compress (const std::vector< Chunk > &chunks)
	Apply compression.

std::unique_ptr< Base::CompressionData >	compress (const std::vector< Chunk > &chunks, Cycles &comp_lat, Cycles &decomp_lat) override
	Apply the compression process to the cache line.

void	decompress (const CompressionData comp_data, uint64_t data) override
	Apply the decompression process to the compressed data.

Static Protected Member Functions
static DictionaryEntry	toDictionaryEntry (T value)
	Turn a value into a dictionary entry.

static T	fromDictionaryEntry (const DictionaryEntry &entry)
	Turn a dictionary entry into a value.

Static Protected Member Functions inherited from gem5::compression::DictionaryCompressor< T >::Pattern
static DictionaryEntry	toDictionaryEntry (T value)
	Turn a value into a dictionary entry.

static T	fromDictionaryEntry (const DictionaryEntry &entry)
	Turn a dictionary entry into a value.

Protected Attributes
std::vector< DictionaryEntry >	dictionary
	The dictionary.

Protected Attributes inherited from gem5::compression::BaseDictionaryCompressor
const std::size_t	dictionarySize
	Dictionary size.

std::size_t	numEntries
	Number of valid entries in the dictionary.

gem5::compression::BaseDictionaryCompressor::DictionaryStats	dictionaryStats

Protected Attributes inherited from gem5::compression::Base
const std::size_t	blkSize
	Uncompressed cache line size (in bytes).

const unsigned	chunkSizeBits
	Chunk size, in number of bits.

const std::size_t	sizeThreshold
	Size in bytes at which a compression is classified as bad and therefore the compressed block is restored to its uncompressed format.

const Cycles	compChunksPerCycle
	Degree of parallelization of the compression process.

const Cycles	compExtraLatency
	Extra latency added to compression due to packaging, shifting or other operations.

const Cycles	decompChunksPerCycle
	Degree of parallelization of the decompression process.

const Cycles	decompExtraLatency
	Extra latency added to decompression due to packaging, shifting or other operations.

BaseCache *	cache
	Pointer to the parent cache.

gem5::compression::Base::BaseStats	stats

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.

Protected Attributes inherited from gem5::compression::DictionaryCompressor< T >::Pattern
const int	patternNumber
	Pattern enum number.

const uint8_t	code
	Code associated to the pattern.

const uint8_t	length
	Length, in bits, of the code and match location.

const uint8_t	numUnmatchedBits
	Number of unmatched bits.

const int	matchLocation
	Index representing the the match location.

const bool	allocate
	Wether the pattern allocates a dictionary entry or not.

std::vector< DictionaryEntry >	dictionary
	The dictionary.

Private Attributes
const DictionaryEntry	bytes
	The original value.

Detailed Description

template<class T>
template<std::size_t DeltaSizeBits>
class gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >

A pattern that checks whether the difference of the value and the dictionary entries' is below a certain threshold.

If so, the pattern is successful, and only the delta bits need to be stored.

For example, if the delta can only contain up to 4 bits, and the dictionary contains the entry 0xA231, the value 0xA232 would be compressible, and the delta 0x1 would be stored. The value 0xA249, on the other hand, would not be compressible, since its delta (0x18) needs 5 bits to be stored.

Template Parameters

DeltaSizeBits Size of a delta entry, in number of bits, which determines the threshold. Must always be smaller than the dictionary entry type's size.

Definition at line 682 of file dictionary_compressor.hh.

Member Typedef Documentation

◆ DictionaryEntry

typedef std::array<uint8_t, sizeof(T)> gem5::compression::DictionaryCompressor< T >::DictionaryEntry

protected

Convenience typedef for a dictionary entry.

Definition at line 121 of file dictionary_compressor.hh.

◆ Params

typedef BaseDictionaryCompressorParams gem5::compression::DictionaryCompressor< T >::Params

Definition at line 273 of file dictionary_compressor.hh.

Constructor & Destructor Documentation

◆ DeltaPattern()

template<class T>

template<std::size_t DeltaSizeBits>

gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >::DeltaPattern	(	const int	number,
		const uint64_t	code,
		const uint64_t	metadata_length,
		const int	match_location,
		const DictionaryEntry	bytes )

inline

Definition at line 697 of file dictionary_compressor.hh.

References bytes, gem5::compression::DictionaryCompressor< T >::Pattern::code, DictionaryCompressor(), and gem5::compression::DictionaryCompressor< T >::Pattern::Pattern().

◆ ~DictionaryCompressor()

gem5::compression::DictionaryCompressor< T >::~DictionaryCompressor ( )

default

Member Function Documentation

◆ addToDictionary()

virtual void gem5::compression::DictionaryCompressor< T >::addToDictionary ( const DictionaryEntry data )

protectedpure virtual

Add an entry to the dictionary.

Parameters

data	The new entry.

Implements gem5::compression::DictionaryCompressor< T >::Pattern.

◆ compress() [1/2]

std::unique_ptr< Base::CompressionData > gem5::compression::DictionaryCompressor< T >::compress ( const std::vector< Chunk > & chunks )

protected

Apply compression.

Parameters

chunks The cache line to be compressed.

Returns: Cache line after compression.

Definition at line 245 of file dictionary_compressor_impl.hh.

◆ compress() [2/2]

std::unique_ptr< Base::CompressionData > gem5::compression::DictionaryCompressor< T >::compress	(	const std::vector< Chunk > &	chunks,
		Cycles &	comp_lat,
		Cycles &	decomp_lat )

overrideprotectedvirtual

Apply the compression process to the cache line.

Returns the number of cycles used by the compressor, however it is usually covered by a good pipelined execution, and is currently ignored. The decompression latency is also returned, in order to avoid increasing simulation time and memory consumption.

Parameters

chunks	The cache line to be compressed, divided into chunks.
comp_lat	Compression latency in number of cycles.
decomp_lat	Decompression latency in number of cycles.

Returns: Cache line after compression.

Implements gem5::compression::Base.

Definition at line 248 of file dictionary_compressor_impl.hh.

◆ compressValue()

std::unique_ptr< typename DictionaryCompressor< T >::Pattern > gem5::compression::DictionaryCompressor< T >::compressValue ( const T data )

protected

Compress data.

Parameters

data	Data to be compressed.

Returns: The pattern this data matches.

Definition at line 211 of file dictionary_compressor_impl.hh.

◆ decompress() [1/2]

void gem5::compression::DictionaryCompressor< T >::decompress	(	const CompressionData *	comp_data,
		uint64_t *	data )

overrideprotectedvirtual

Apply the decompression process to the compressed data.

Parameters

comp_data	Compressed cache line.
cache_line	The cache line to be decompressed.

Implements gem5::compression::Base.

Definition at line 254 of file dictionary_compressor_impl.hh.

◆ decompress() [2/2]

template<class T>

template<std::size_t DeltaSizeBits>

DictionaryEntry gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >::decompress ( const DictionaryEntry dict_bytes ) const

inlineoverridevirtual

Decompress the pattern.

Each pattern has its own way of interpreting its data.

Parameters

dict_bytes The bytes in the corresponding matching entry.

Returns: The decompressed pattern.

Implements gem5::compression::DictionaryCompressor< T >::Pattern.

Definition at line 738 of file dictionary_compressor.hh.

References bytes.

◆ decompressValue()

T gem5::compression::DictionaryCompressor< T >::decompressValue ( const Pattern * pattern )

protected

Decompress a pattern into a value that fits in a dictionary entry.

Parameters

pattern The pattern to be decompressed.

Returns: The decompressed word.

Definition at line 219 of file dictionary_compressor_impl.hh.

◆ DictionaryCompressor()

gem5::compression::DictionaryCompressor< T >::DictionaryCompressor ( const Params & p )

Definition at line 274 of file dictionary_compressor_impl.hh.

Referenced by DeltaPattern().

◆ fromDictionaryEntry()

T gem5::compression::DictionaryCompressor< T >::fromDictionaryEntry ( const DictionaryEntry & entry )

staticprotected

Turn a dictionary entry into a value.

Parameters

The	dictionary entry to turn.

Returns: The value that the dictionary entry contained.

Definition at line 270 of file dictionary_compressor_impl.hh.

◆ getPattern()

virtual std::unique_ptr< Pattern > gem5::compression::DictionaryCompressor< T >::getPattern	(	const DictionaryEntry &	bytes,
		const DictionaryEntry &	dict_bytes,
		const int	match_location ) const

protectedpure virtual

Since the factory cannot be instantiated here, classes that inherit from this base class have to implement the call to their factory's getPattern.

Implements gem5::compression::DictionaryCompressor< T >::Pattern.

◆ instantiateDictionaryCompData()

std::unique_ptr< typename DictionaryCompressor< T >::CompData > gem5::compression::DictionaryCompressor< T >::instantiateDictionaryCompData ( ) const

protectedvirtual

Instantiate a compression data of the sub-class compressor.

Returns: The new compression data entry.

Reimplemented from gem5::compression::DictionaryCompressor< T >::Pattern.

Definition at line 237 of file dictionary_compressor_impl.hh.

◆ isPattern()

template<class T>

template<std::size_t DeltaSizeBits>

static bool gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >::isPattern	(	const DictionaryEntry &	bytes,
		const DictionaryEntry &	dict_bytes,
		const int	match_location )

inlinestatic

Definition at line 731 of file dictionary_compressor.hh.

References bytes, and isValidDelta().

◆ isValidDelta()

template<class T>

template<std::size_t DeltaSizeBits>

static bool gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >::isValidDelta	(	const DictionaryEntry &	bytes,
		const DictionaryEntry &	base_bytes )

inlinestatic

Compares a given value against a base to calculate their delta, and then determines whether it fits a limited sized container.

Parameters

bytes	Value to be compared against base.
base_bytes	Base value.

Returns: Whether the value fits in the container.

Definition at line 717 of file dictionary_compressor.hh.

References gem5::RiscvISA::base, bytes, gem5::compression::DictionaryCompressor< T >::fromDictionaryEntry(), gem5::X86ISA::limit, and gem5::ArmISA::mask.

Referenced by isPattern().

◆ resetDictionary()

void gem5::compression::DictionaryCompressor< T >::resetDictionary ( )

protectedvirtual

Clear all dictionary entries.

Reimplemented from gem5::compression::DictionaryCompressor< T >::Pattern.

Definition at line 222 of file dictionary_compressor_impl.hh.

◆ toDictionaryEntry()

DictionaryCompressor< T >::DictionaryEntry gem5::compression::DictionaryCompressor< T >::toDictionaryEntry ( T value )

staticprotected

Turn a value into a dictionary entry.

Parameters

value The value to turn.

Returns: A dictionary entry containing the value.

Definition at line 262 of file dictionary_compressor_impl.hh.

Member Data Documentation

◆ bytes

template<class T>

template<std::size_t DeltaSizeBits>

const DictionaryEntry gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >::bytes

private

The original value.

In theory we should keep only the deltas, but the dictionary entry is not inserted in the dictionary before the call to the constructor, so the delta cannot be calculated then.

Definition at line 694 of file dictionary_compressor.hh.

Referenced by decompress(), DeltaPattern(), isPattern(), and isValidDelta().

◆ dictionary

std::vector<DictionaryEntry> gem5::compression::DictionaryCompressor< T >::dictionary

protected

The dictionary.

Definition at line 194 of file dictionary_compressor.hh.

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

mem/cache/compressors/dictionary_compressor.hh
mem/cache/compressors/dictionary_compressor_impl.hh

Public Types

Public Member Functions

Static Public Member Functions

Protected Types

Protected Member Functions

Static Protected Member Functions

Protected Attributes

Private Attributes

Detailed Description

Member Typedef Documentation

◆ DictionaryEntry

◆ Params

Constructor & Destructor Documentation

◆ DeltaPattern()

◆ ~DictionaryCompressor()

Member Function Documentation

◆ addToDictionary()

◆ compress() [1/2]

◆ compress() [2/2]

◆ compressValue()

◆ decompress() [1/2]

◆ decompress() [2/2]

◆ decompressValue()

◆ DictionaryCompressor()

◆ fromDictionaryEntry()

◆ getPattern()

◆ instantiateDictionaryCompData()

◆ isPattern()

◆ isValidDelta()

◆ resetDictionary()

◆ toDictionaryEntry()

Member Data Documentation

◆ bytes

◆ dictionary