gem5  v21.1.0.2
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gem5::compression::Base Class Referenceabstract

Base cache compressor interface. More...

#include <base.hh>

Inheritance diagram for gem5::compression::Base:
gem5::SimObject gem5::EventManager gem5::Serializable gem5::Drainable gem5::statistics::Group gem5::Named gem5::compression::BaseDictionaryCompressor gem5::compression::FrequentValues gem5::compression::Multi gem5::compression::Perfect gem5::compression::DictionaryCompressor< BaseType > gem5::compression::DictionaryCompressor< uint16_t > gem5::compression::DictionaryCompressor< uint32_t > gem5::compression::DictionaryCompressor< uint64_t > gem5::compression::DictionaryCompressor< T > gem5::compression::BaseDelta< BaseType, DeltaSizeBits > gem5::compression::BaseDelta< uint16_t, 8 > gem5::compression::BaseDelta< uint32_t, 16 > gem5::compression::BaseDelta< uint32_t, 8 > gem5::compression::CPack gem5::compression::FPC gem5::compression::FPCD gem5::compression::BaseDelta< uint64_t, 16 > gem5::compression::BaseDelta< uint64_t, 32 > gem5::compression::BaseDelta< uint64_t, 8 > gem5::compression::RepeatedQwords gem5::compression::Zero

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. More...
 
std::unique_ptr< CompressionDatacompress (const uint64_t *data, Cycles &comp_lat, Cycles &decomp_lat)
 Apply the compression process to the cache line. More...
 
Cycles getDecompressionLatency (const CacheBlk *blk)
 Get the decompression latency if the block is compressed. More...
 
- Public Member Functions inherited from gem5::SimObject
const Paramsparams () 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. 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...
 
virtual void regProbeListeners ()
 Register probe listeners 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 gem5::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 gem5::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 gem5::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 gem5::statistics::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 (statistics::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...
 
void mergeStatGroup (Group *block)
 Merge the contents (stats & children) of a block to this block. More...
 
 Group ()=delete
 
 Group (const Group &)=delete
 
Groupoperator= (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. More...
 
static void setSizeBits (CacheBlk *blk, const std::size_t size_bits)
 Set the size of the compressed block, in bits. More...
 
- 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. More...
 
static SimObjectfind (const char *name)
 Find the SimObject with the given name and return a pointer to it. More...
 
static void setSimObjectResolver (SimObjectResolver *resolver)
 There is a single object name resolver, and it is only set when simulation is restoring from checkpoints. More...
 
static SimObjectResolvergetSimObjectResolver ()
 There is a single object name resolver, and it is only set when simulation is restoring from checkpoints. More...
 
- Static Public Member Functions inherited from gem5::Serializable
static const std::string & currentSection ()
 Gets the fully-qualified name of the active section. More...
 
static void generateCheckpointOut (const std::string &cpt_dir, std::ofstream &outstream)
 Generate a checkpoint file so that the serialization can be routed to it. More...
 

Protected Types

typedef uint64_t Chunk
 A chunk is a basic lexical unit. More...
 

Protected Member Functions

std::vector< ChunktoChunks (const uint64_t *data) const
 This function splits the raw data into chunks, so that it can be parsed by the compressor. More...
 
void fromChunks (const std::vector< Chunk > &chunks, uint64_t *data) const
 This function re-joins the chunks to recreate the original data. More...
 
virtual std::unique_ptr< CompressionDatacompress (const std::vector< Chunk > &chunks, Cycles &comp_lat, Cycles &decomp_lat)=0
 Apply the compression process to the cache line. More...
 
virtual void decompress (const CompressionData *comp_data, uint64_t *cache_line)=0
 Apply the decompression process to the compressed data. More...
 
- Protected Member Functions inherited from gem5::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 Attributes

const std::size_t blkSize
 Uncompressed cache line size (in bytes). More...
 
const unsigned chunkSizeBits
 Chunk size, in number of bits. More...
 
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. More...
 
const Cycles compChunksPerCycle
 Degree of parallelization of the compression process. More...
 
const Cycles compExtraLatency
 Extra latency added to compression due to packaging, shifting or other operations. More...
 
const Cycles decompChunksPerCycle
 Degree of parallelization of the decompression process. More...
 
const Cycles decompExtraLatency
 Extra latency added to decompression due to packaging, shifting or other operations. More...
 
BaseCachecache
 Pointer to the parent cache. More...
 
gem5::compression::Base::BaseStats stats
 
- Protected Attributes inherited from gem5::SimObject
const SimObjectParams & _params
 Cached copy of the object parameters. More...
 
- Protected Attributes inherited from gem5::EventManager
EventQueueeventq
 A pointer to this object's event queue. More...
 

Friends

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

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 65 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 72 of file base.hh.

◆ Params

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

Definition at line 202 of file base.hh.

Constructor & Destructor Documentation

◆ Base()

Base::Base ( const Params p)

◆ ~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
chunksThe cache line to be compressed, divided into chunks.
comp_latCompression latency in number of cycles.
decomp_latDecompression latency in number of cycles.
Returns
Cache line after compression.

Implemented in gem5::compression::DictionaryCompressor< T >, gem5::compression::DictionaryCompressor< uint32_t >, gem5::compression::DictionaryCompressor< uint16_t >, gem5::compression::DictionaryCompressor< BaseType >, gem5::compression::DictionaryCompressor< uint64_t >, gem5::compression::FrequentValues, gem5::compression::Perfect, gem5::compression::BaseDelta< BaseType, DeltaSizeBits >, gem5::compression::BaseDelta< uint64_t, 32 >, gem5::compression::BaseDelta< uint32_t, 16 >, gem5::compression::BaseDelta< uint32_t, 8 >, gem5::compression::BaseDelta< uint64_t, 8 >, gem5::compression::BaseDelta< uint16_t, 8 >, gem5::compression::BaseDelta< uint64_t, 16 >, gem5::compression::Multi, gem5::compression::RepeatedQwords, and gem5::compression::Zero.

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
dataThe cache line to be compressed.
comp_latCompression latency in number of cycles.
decomp_latDecompression latency in number of cycles.
Returns
Cache line after compression.

Definition at line 151 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

◆ 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
chunksThe raw data divided into a vector of sequential chunks.
dataThe raw pointer to the data.

Definition at line 134 of file base.cc.

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

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

◆ getDecompressionLatency()

Cycles Base::getDecompressionLatency ( const CacheBlk blk)

Get the decompression latency if the block is compressed.

Latency is 0 otherwise.

Parameters
blkThe compressed block.

Definition at line 197 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 108 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
blkThe compressed block.
latThe decompression latency.

Definition at line 215 of file base.cc.

Referenced by gem5::BaseCache::allocateBlock().

◆ setSizeBits()

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

Set the size of the compressed block, in bits.

Parameters
blkThe compressed block.
size_bitsThe block size.

Definition at line 225 of file base.cc.

Referenced by gem5::compression::DictionaryCompressor< T >::CompData::addEntry(), gem5::BaseCache::allocateBlock(), gem5::compression::BaseDelta< uint64_t, 16 >::compress(), and gem5::compression::Multi::MultiCompData::MultiCompData().

◆ 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
dataThe raw pointer to the data being compressed.
Returns
The raw data divided into a vector of sequential chunks.

Definition at line 115 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 Function Documentation

◆ Multi

friend class Multi
friend

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

Definition at line 89 of file base.hh.

Member Data Documentation

◆ blkSize

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

◆ cache

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

Pointer to the parent cache.

Definition at line 130 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 97 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 109 of file base.hh.

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

◆ compExtraLatency

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

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

Definition at line 115 of file base.hh.

Referenced by gem5::compression::Perfect::compress(), gem5::compression::Multi::compress(), and gem5::compression::FrequentValues::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 121 of file base.hh.

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

◆ decompExtraLatency

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

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

Definition at line 127 of file base.hh.

Referenced by gem5::compression::Perfect::compress(), gem5::compression::Multi::compress(), and gem5::compression::FrequentValues::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 103 of file base.hh.

Referenced by Base(), and compress().

◆ stats

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

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

Generated on Tue Sep 21 2021 12:28:50 for gem5 by doxygen 1.8.17