Base cache compressor interface. More...

#include <base.hh>

Inheritance diagram for gem5::compression::Base:

Classes
struct	BaseStats

class	CompressionData

Public Types
typedef BaseCacheCompressorParams	Params

Public Types inherited from gem5::SimObject
typedef SimObjectParams	Params

Public Member Functions
	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

Static Public Member Functions
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 uint64_t	Chunk
	A chunk is a basic lexical unit.

Protected Member Functions
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.

virtual std::unique_ptr< CompressionData >	compress (const std::vector< Chunk > &chunks, Cycles &comp_lat, Cycles &decomp_lat)=0
	Apply the compression process to the cache line.

virtual void	decompress (const CompressionData comp_data, uint64_t cache_line)=0
	Apply the decompression process to the compressed 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 Attributes
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.

Friends
class	Multi
	This compressor must be able to access the protected functions of its sub-compressors.

Detailed Description

Base cache compressor interface.

Every cache compressor must implement a compression and a decompression method.

Compressors usually cannot parse all data input at once. Therefore, they typically divide the input into multiple chunks, and parse them one at a cycle.

Definition at line 64 of file base.hh.

Member Typedef Documentation

◆ Chunk

typedef uint64_t gem5::compression::Base::Chunk

protected

A chunk is a basic lexical unit.

The data being compressed is received by the compressor as a raw pointer. In order to parse this data, the compressor must divide it into smaller units. Typically, state-of-the- art compressors interpret cache lines as sequential 32-bit chunks (chunks), but any size is valid.

See also: chunkSizeBits

Definition at line 82 of file base.hh.

◆ Params

typedef BaseCacheCompressorParams gem5::compression::Base::Params

Definition at line 201 of file base.hh.

Constructor & Destructor Documentation

◆ Base()

Base::Base ( const Params & p )

Definition at line 84 of file base.cc.

References blkSize, chunkSizeBits, compChunksPerCycle, decompChunksPerCycle, fatal_if, and sizeThreshold.

◆ ~Base()

virtual gem5::compression::Base::~Base ( )

virtualdefault

Member Function Documentation

◆ compress() [1/2]

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

protectedpure virtual

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.

Referenced by gem5::BaseCache::allocateBlock(), compress(), and gem5::BaseCache::updateCompressionData().

◆ compress() [2/2]

std::unique_ptr< Base::CompressionData > Base::compress	(	const uint64_t *	data,
		Cycles &	comp_lat,
		Cycles &	decomp_lat )

Apply the compression process to the cache line.

Ignores compression cycles.

Parameters

data	The cache line to be compressed.
comp_lat	Compression latency in number of cycles.
decomp_lat	Decompression latency in number of cycles.

Returns: Cache line after compression.

Definition at line 150 of file base.cc.

References blkSize, compress(), gem5::compression::Base::BaseStats::compressions, gem5::compression::Base::BaseStats::compressionSize, gem5::compression::Base::BaseStats::compressionSizeBits, data, decompress(), DPRINTF, gem5::compression::Base::BaseStats::failedCompressions, fatal_if, sizeThreshold, stats, and toChunks().

◆ decompress()

virtual void gem5::compression::Base::decompress	(	const CompressionData *	comp_data,
		uint64_t *	cache_line )

protectedpure virtual

Apply the decompression process to the compressed data.

Parameters

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

Implemented in gem5::compression::DictionaryCompressor< T >, gem5::compression::DictionaryCompressor< BaseType >, gem5::compression::DictionaryCompressor< uint16_t >, gem5::compression::DictionaryCompressor< uint32_t >, gem5::compression::DictionaryCompressor< uint64_t >, gem5::compression::FrequentValues, gem5::compression::Multi, and gem5::compression::Perfect.

Referenced by compress().

◆ fromChunks()

void Base::fromChunks	(	const std::vector< Chunk > &	chunks,
		uint64_t *	data ) const

protected

This function re-joins the chunks to recreate the original data.

Parameters

chunks	The raw data divided into a vector of sequential chunks.
data	The raw pointer to the data.

Definition at line 133 of file base.cc.

References blkSize, chunkSizeBits, data, gem5::ArmISA::i, and gem5::replaceBits().

Referenced by gem5::compression::Multi::compress(), gem5::compression::FrequentValues::decompress(), and gem5::compression::Perfect::decompress().

◆ getDecompressionLatency()

Cycles Base::getDecompressionLatency ( const CacheBlk * blk )

Get the decompression latency if the block is compressed.

Latency is 0 otherwise.

Parameters

blk	The compressed block.

Definition at line 196 of file base.cc.

References gem5::compression::Base::BaseStats::decompressions, DPRINTF, gem5::CompressionBlk::getDecompressionLatency(), gem5::CompressionBlk::isCompressed(), gem5::CompressionBlk::print(), and stats.

Referenced by gem5::BaseCache::access(), gem5::Cache::handleSnoop(), gem5::BaseCache::writebackBlk(), and gem5::BaseCache::writecleanBlk().

◆ setCache()

void Base::setCache ( BaseCache * _cache )

virtual

The cache can only be set once.

Reimplemented in gem5::compression::Multi.

Definition at line 107 of file base.cc.

References cache.

Referenced by gem5::compression::Multi::setCache().

◆ setDecompressionLatency()

void Base::setDecompressionLatency	(	CacheBlk *	blk,
		const Cycles	lat )

static

Set the decompression latency of compressed block.

Parameters

blk	The compressed block.
lat	The decompression latency.

Definition at line 214 of file base.cc.

References setDecompressionLatency().

Referenced by gem5::BaseCache::allocateBlock(), and setDecompressionLatency().

◆ setSizeBits()

void Base::setSizeBits	(	CacheBlk *	blk,
		const std::size_t	size_bits )

static

Set the size of the compressed block, in bits.

Parameters

blk	The compressed block.
size_bits	The block size.

Definition at line 224 of file base.cc.

References setSizeBits().

Referenced by gem5::compression::DictionaryCompressor< T >::CompData::addEntry(), gem5::BaseCache::allocateBlock(), gem5::compression::BaseDelta< BaseType, DeltaSizeBits >::compress(), and setSizeBits().

◆ toChunks()

std::vector< Base::Chunk > Base::toChunks ( const uint64_t * data ) const

protected

This function splits the raw data into chunks, so that it can be parsed by the compressor.

Parameters

data	The raw pointer to the data being compressed.

Returns: The raw data divided into a vector of sequential chunks.

Definition at line 114 of file base.cc.

References gem5::bits(), blkSize, chunkSizeBits, data, and gem5::ArmISA::i.

Referenced by compress(), and gem5::compression::FrequentValues::sampleValues().

Friends And Related Symbol Documentation

◆ Multi

friend class Multi

friend

This compressor must be able to access the protected functions of its sub-compressors.

Definition at line 88 of file base.hh.

Member Data Documentation

◆ blkSize

const std::size_t gem5::compression::Base::blkSize

protected

Uncompressed cache line size (in bytes).

Definition at line 93 of file base.hh.

Referenced by Base(), compress(), gem5::compression::Multi::compress(), gem5::compression::RepeatedQwords::compress(), gem5::compression::Zero::compress(), fromChunks(), and toChunks().

◆ cache

BaseCache* gem5::compression::Base::cache

protected

Pointer to the parent cache.

Definition at line 129 of file base.hh.

Referenced by gem5::compression::FrequentValues::regProbeListeners(), and setCache().

◆ chunkSizeBits

const unsigned gem5::compression::Base::chunkSizeBits

protected

Chunk size, in number of bits.

Definition at line 96 of file base.hh.

Referenced by Base(), gem5::compression::FrequentValues::compress(), fromChunks(), and toChunks().

◆ compChunksPerCycle

const Cycles gem5::compression::Base::compChunksPerCycle

protected

Degree of parallelization of the compression process.

It is the number of chunks that can be processed in a cycle.

Definition at line 108 of file base.hh.

Referenced by Base(), gem5::compression::FrequentValues::compress(), and gem5::compression::Perfect::compress().

◆ compExtraLatency

const Cycles gem5::compression::Base::compExtraLatency

protected

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

Definition at line 114 of file base.hh.

Referenced by gem5::compression::FrequentValues::compress(), gem5::compression::Multi::compress(), and gem5::compression::Perfect::compress().

◆ decompChunksPerCycle

const Cycles gem5::compression::Base::decompChunksPerCycle

protected

Degree of parallelization of the decompression process.

It is the number of chunks that can be processed in a cycle.

Definition at line 120 of file base.hh.

Referenced by Base(), gem5::compression::FrequentValues::compress(), and gem5::compression::Perfect::compress().

◆ decompExtraLatency

const Cycles gem5::compression::Base::decompExtraLatency

protected

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

Definition at line 126 of file base.hh.

Referenced by gem5::compression::FrequentValues::compress(), gem5::compression::Multi::compress(), and gem5::compression::Perfect::compress().

◆ sizeThreshold

const std::size_t gem5::compression::Base::sizeThreshold

protected

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

Definition at line 102 of file base.hh.

Referenced by Base(), and compress().

◆ stats

gem5::compression::Base::BaseStats gem5::compression::Base::stats

protected

Referenced by compress(), and getDecompressionLatency().

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

mem/cache/compressors/base.hh
mem/cache/compressors/base.cc

Classes

Public Types

Public Member Functions

Static Public Member Functions

Protected Types

Protected Member Functions

Protected Attributes

Friends

Detailed Description

Member Typedef Documentation

◆ Chunk

◆ Params

Constructor & Destructor Documentation

◆ Base()

◆ ~Base()

Member Function Documentation

◆ compress() [1/2]

◆ compress() [2/2]

◆ decompress()

◆ fromChunks()

◆ getDecompressionLatency()

◆ setCache()

◆ setDecompressionLatency()

◆ setSizeBits()

◆ toChunks()

Friends And Related Symbol Documentation

◆ Multi

Member Data Documentation

◆ blkSize

◆ cache

◆ chunkSizeBits

◆ compChunksPerCycle

◆ compExtraLatency

◆ decompChunksPerCycle

◆ decompExtraLatency

◆ sizeThreshold

◆ stats