Base class for all base-delta-immediate compressors. More...

#include <base_delta.hh>

Inheritance diagram for gem5::compression::BaseDelta< BaseType, DeltaSizeBits >:

Classes
class	PatternM

class	PatternX

Public Types
typedef BaseDictionaryCompressorParams	Params

Public Types inherited from gem5::compression::DictionaryCompressor< BaseType >
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 Member Functions
	BaseDelta (const Params &p)

	~BaseDelta ()=default

Public Member Functions inherited from gem5::compression::DictionaryCompressor< BaseType >
	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 (const std::string &name_)

virtual	~Named ()=default

virtual std::string	name () const

Protected Types
enum	PatternNumber { X , M , NUM_PATTERNS }
	The patterns proposed in the paper. More...

using	DictionaryEntry

using	PatternFactory
	Convenience factory declaration.

Protected Types inherited from gem5::compression::DictionaryCompressor< BaseType >
typedef std::array< uint8_t, sizeof(BaseType)>	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 Member Functions
uint64_t	getNumPatterns () const override
	Trick function to get the number of patterns.

std::unique_ptr< typename DictionaryCompressor< BaseType >::Pattern >	getPattern (const DictionaryEntry &bytes, const DictionaryEntry &dict_bytes, const int match_location) const override

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

void	resetDictionary () override
	Clear all dictionary entries.

void	addToDictionary (DictionaryEntry data) override

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

Protected Member Functions inherited from gem5::compression::DictionaryCompressor< BaseType >
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 BaseType data)
	Compress data.

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

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::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.

Static Protected Attributes
static constexpr int	DEFAULT_MAX_NUM_BASES = 2

Additional Inherited Members
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.

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

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

Protected Attributes inherited from gem5::compression::DictionaryCompressor< BaseType >
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.

Detailed Description

template<class BaseType, std::size_t DeltaSizeBits>
class gem5::compression::BaseDelta< BaseType, DeltaSizeBits >

Base class for all base-delta-immediate compressors.

Although not proposed like this in the original paper, the sub-compressors of BDI are dictionary based with 2 possible patterns: no match, where a dictionary entry must be allocated, and masked delta match with a dictionary entry, where the delta must be stored instead. The maximum number of dictionary entries is 2, and one of them is reserved for a zero base if using immediate compression.

Template Parameters

BaseType Type of a base (dictionary) entry.

Definition at line 69 of file base_delta.hh.

Member Typedef Documentation

◆ DictionaryEntry

template<class BaseType , std::size_t DeltaSizeBits>

using gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::DictionaryEntry

protected

Initial value:

typename DictionaryCompressor<BaseType>::DictionaryEntry

gem5::compression::DictionaryCompressor::DictionaryEntry

std::array< uint8_t, sizeof(T)> DictionaryEntry

Convenience typedef for a dictionary entry.

Definition dictionary_compressor.hh:121

Definition at line 74 of file base_delta.hh.

◆ Params

template<class BaseType , std::size_t DeltaSizeBits>

typedef BaseDictionaryCompressorParams gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::Params

Definition at line 128 of file base_delta.hh.

◆ PatternFactory

template<class BaseType , std::size_t DeltaSizeBits>

using gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::PatternFactory

protected

Initial value:

typename DictionaryCompressor<BaseType>::template

Factory<PatternM, PatternX>

Convenience factory declaration.

The templates must be organized by size, with the smallest first, and "no-match" last.

Definition at line 98 of file base_delta.hh.

Member Enumeration Documentation

◆ PatternNumber

template<class BaseType , std::size_t DeltaSizeBits>

enum gem5::compression::BaseDelta::PatternNumber

protected

The patterns proposed in the paper.

Each letter represents a byte: Z is a null byte, M is a dictionary match, X is a new value. These are used as indexes to reference the pattern data. If a new pattern is added, it must be done before NUM_PATTERNS.

Enumerator
X
M
NUM_PATTERNS

Definition at line 87 of file base_delta.hh.

Constructor & Destructor Documentation

◆ BaseDelta()

template<class BaseType , std::size_t DeltaSizeBits>

gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::BaseDelta ( const Params & p )

Definition at line 47 of file base_delta_impl.hh.

◆ ~BaseDelta()

template<class BaseType , std::size_t DeltaSizeBits>

gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::~BaseDelta ( )

default

Member Function Documentation

◆ addToDictionary()

template<class BaseType , std::size_t DeltaSizeBits>

void gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::addToDictionary ( DictionaryEntry data )

overrideprotected

Definition at line 64 of file base_delta_impl.hh.

References data.

◆ compress()

template<class BaseType , std::size_t DeltaSizeBits>

std::unique_ptr< Base::CompressionData > gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::compress	(	const std::vector< Base::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 74 of file base_delta_impl.hh.

References gem5::compression::DictionaryCompressor< T >::compress(), DPRINTF, and gem5::compression::Base::setSizeBits().

◆ getName()

template<class BaseType , std::size_t DeltaSizeBits>

std::string gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::getName ( int number ) const

inlineoverrideprotectedvirtual

Get meta-name assigned to the given pattern.

Parameters

number The number of the pattern.

Returns: The meta-name of the pattern.

Implements gem5::compression::BaseDictionaryCompressor.

Definition at line 110 of file base_delta.hh.

References gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::M, and gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::X.

◆ getNumPatterns()

template<class BaseType , std::size_t DeltaSizeBits>

uint64_t gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::getNumPatterns ( ) const

inlineoverrideprotectedvirtual

Trick function to get the number of patterns.

Returns: The number of defined patterns.

Implements gem5::compression::BaseDictionaryCompressor.

Definition at line 92 of file base_delta.hh.

References gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::NUM_PATTERNS.

◆ getPattern()

template<class BaseType , std::size_t DeltaSizeBits>

std::unique_ptr< typename DictionaryCompressor< BaseType >::Pattern > gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::getPattern	(	const DictionaryEntry &	bytes,
		const DictionaryEntry &	dict_bytes,
		const int	match_location ) const

inlineoverrideprotected

Definition at line 102 of file base_delta.hh.

◆ resetDictionary()

template<class BaseType , std::size_t DeltaSizeBits>

void gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::resetDictionary ( )

overrideprotectedvirtual

Clear all dictionary entries.

Reimplemented from gem5::compression::DictionaryCompressor< BaseType >.

Definition at line 54 of file base_delta_impl.hh.

References gem5::compression::DictionaryCompressor< T >::resetDictionary().

Member Data Documentation

◆ DEFAULT_MAX_NUM_BASES

template<class BaseType , std::size_t DeltaSizeBits>

int gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::DEFAULT_MAX_NUM_BASES = 2

staticconstexprprotected

Definition at line 72 of file base_delta.hh.

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

mem/cache/compressors/base_delta.hh
mem/cache/compressors/base_delta_impl.hh

Classes

Public Types

Public Member Functions

Protected Types

Protected Member Functions

Static Protected Attributes

Additional Inherited Members

Detailed Description

Member Typedef Documentation

◆ DictionaryEntry

◆ Params

◆ PatternFactory

Member Enumeration Documentation

◆ PatternNumber

Constructor & Destructor Documentation

◆ BaseDelta()

◆ ~BaseDelta()

Member Function Documentation

◆ addToDictionary()

◆ compress()

◆ getName()

◆ getNumPatterns()

◆ getPattern()

◆ resetDictionary()

Member Data Documentation

◆ DEFAULT_MAX_NUM_BASES