A CompressedTags cache tag store. More...

#include <compressed_tags.hh>

Inheritance diagram for gem5::CompressedTags:

Public Types
typedef CompressedTagsParams	Params
	Convenience typedef.

Public Types inherited from gem5::SectorTags
typedef SectorTagsParams	Params
	Convenience typedef.

Public Types inherited from gem5::BaseTags
typedef BaseTagsParams	Params

Public Types inherited from gem5::ClockedObject
using	Params = ClockedObjectParams
	Parameters of ClockedObject.

Public Types inherited from gem5::SimObject
typedef SimObjectParams	Params

Public Member Functions
	CompressedTags (const Params &p)
	Construct and initialize this tag store.

virtual	~CompressedTags ()
	Destructor.

void	tagsInit () override
	Initialize blocks as SuperBlk and CompressionBlk instances.

CacheBlk *	findVictim (Addr addr, const bool is_secure, const std::size_t compressed_size, std::vector< CacheBlk * > &evict_blks, const uint64_t partition_id) override
	Find replacement victim based on address.

bool	anyBlk (std::function< bool(CacheBlk &)> visitor) override
	Find if any of the sub-blocks satisfies a condition.

Public Member Functions inherited from gem5::SectorTags
	SectorTags (const Params &p)
	Construct and initialize this tag store.

virtual	~SectorTags ()
	Destructor.

void	tagsInit () override
	Initialize blocks as SectorBlk and SectorSubBlk instances.

void	invalidate (CacheBlk *blk) override
	This function updates the tags when a block is invalidated but does not invalidate the block itself.

CacheBlk *	accessBlock (const PacketPtr pkt, Cycles &lat) override
	Access block and update replacement data.

void	insertBlock (const PacketPtr pkt, CacheBlk *blk) override
	Insert the new block into the cache and update replacement data.

void	moveBlock (CacheBlk src_blk, CacheBlk dest_blk) override
	Move a block's metadata to another location decided by the replacement policy.

CacheBlk *	findBlock (Addr addr, bool is_secure) const override
	Finds the given address in the cache, do not update replacement data.

CacheBlk *	findVictim (Addr addr, const bool is_secure, const std::size_t size, std::vector< CacheBlk * > &evict_blks, const uint64_t partition_id) override
	Find replacement victim based on address.

int	extractSectorOffset (Addr addr) const
	Calculate a block's offset in a sector from the address.

Addr	regenerateBlkAddr (const CacheBlk *blk) const override
	Regenerate the block address from the tag and location.

bool	anyBlk (std::function< bool(CacheBlk &)> visitor) override
	Find if any of the sub-blocks satisfies a condition.

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

virtual	~BaseTags ()
	Destructor.

void	cleanupRefs ()
	Average in the reference count for valid blocks when the simulation exits.

void	computeStats ()
	Computes stats just prior to dump event.

std::string	print ()
	Print all tags used.

virtual ReplaceableEntry *	findBlockBySetAndWay (int set, int way) const
	Find a block given set and way.

Addr	blkAlign (Addr addr) const
	Align an address to the block size.

int	extractBlkOffset (Addr addr) const
	Calculate the block offset of an address.

virtual void	setWayAllocationMax (int ways)
	Limit the allocation for the cache ways.

virtual int	getWayAllocationMax () const
	Get the way allocation mask limit.

virtual Addr	extractTag (const Addr addr) const
	Generate the tag from the given address.

void	forEachBlk (std::function< void(CacheBlk &)> visitor)
	Visit each block in the tags and apply a visitor.

Public Member Functions inherited from gem5::ClockedObject
	ClockedObject (const ClockedObjectParams &p)

void	serialize (CheckpointOut &cp) const override
	Serialize an object.

void	unserialize (CheckpointIn &cp) override
	Unserialize an object.

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

Public Member Functions inherited from gem5::Clocked
void	updateClockPeriod ()
	Update the tick to the current tick.

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.

Cycles	curCycle () const
	Determine the current cycle, corresponding to a tick aligned to a clock edge.

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.

uint64_t	frequency () const

Tick	clockPeriod () const

double	voltage () const

Cycles	ticksToCycles (Tick t) const

Tick	cyclesToTicks (Cycles c) const

Private Attributes
std::vector< CompressionBlk >	blks
	The cache blocks.

std::vector< SuperBlk >	superBlks
	The cache superblocks.

Additional Inherited Members
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.

Public Attributes inherited from gem5::ClockedObject
PowerState *	powerState

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::Clocked
	Clocked (ClockDomain &clk_domain)
	Create a clocked object and set the clock domain based on the parameters.

	Clocked (Clocked &)=delete

Clocked &	operator= (Clocked &)=delete

virtual	~Clocked ()
	Virtual destructor due to inheritance.

void	resetClock () const
	Reset the object's clock using the current global tick value.

virtual void	clockPeriodUpdated ()
	A hook subclasses can implement so they can do any extra work that's needed when the clock rate is changed.

Protected Attributes inherited from gem5::SectorTags
unsigned	allocAssoc
	The allocatable associativity of the cache (alloc mask).

const bool	sequentialAccess
	Whether tags and data are accessed sequentially.

replacement_policy::Base *	replacementPolicy
	Replacement policy.

const unsigned	numBlocksPerSector
	Number of data blocks per sector.

const unsigned	numSectors
	The number of sectors in the cache.

const int	sectorShift
	The amount to shift the address to get the sector tag.

const unsigned	sectorMask
	Mask out all bits that aren't part of the sector tag.

gem5::SectorTags::SectorTagsStats	sectorStats

Protected Attributes inherited from gem5::BaseTags
const unsigned	blkSize
	The block size of the cache.

const Addr	blkMask
	Mask out all bits that aren't part of the block offset.

const unsigned	size
	The size of the cache.

const Cycles	lookupLatency
	The tag lookup latency of the cache.

System *	system
	System we are currently operating in.

BaseIndexingPolicy *	indexingPolicy
	Indexing policy.

partitioning_policy::PartitionManager *	partitionManager
	Partitioning manager.

const unsigned	warmupBound
	The number of tags that need to be touched to meet the warmup percentage.

bool	warmedUp
	Marked true when the cache is warmed up.

const unsigned	numBlocks
	the number of blocks in the cache

std::unique_ptr< uint8_t[]>	dataBlks
	The data blocks, 1 per cache block.

gem5::BaseTags::BaseTagStats	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

A CompressedTags cache tag store.

See also: gem5 Memory System

The Compression Ratio (CR) of a superblock is defined by CR = uncompressed_size / compressed_size.

The CompressedTags placement policy divides the cache into s sets of w superblocks (ways). Each superblock can then contain up to CR compressed blocks.

For each tag entry there can be multiple data blocks. We have the same number of tags a conventional cache would have, but we instantiate the maximum number of data blocks (according to the compression ratio) per tag, to virtually implement compression without increasing the complexity of the simulator.

numBlocksPerSector holds the maximum number of blocks a superblock with the best possible compression factor would hold. It is equivalent to CR from the previous definition.

Definition at line 82 of file compressed_tags.hh.

Member Typedef Documentation

◆ Params

typedef CompressedTagsParams gem5::CompressedTags::Params

Convenience typedef.

Definition at line 92 of file compressed_tags.hh.

Constructor & Destructor Documentation

◆ CompressedTags()

gem5::CompressedTags::CompressedTags ( const Params & p )

Construct and initialize this tag store.

Definition at line 60 of file compressed_tags.cc.

◆ ~CompressedTags()

virtual gem5::CompressedTags::~CompressedTags ( )

inlinevirtual

Destructor.

Definition at line 102 of file compressed_tags.hh.

Member Function Documentation

◆ anyBlk()

bool gem5::CompressedTags::anyBlk ( std::function< bool(CacheBlk &)> visitor )

overridevirtual

Find if any of the sub-blocks satisfies a condition.

The visitor should be a std::function that takes a cache block reference as its parameter. The visitor will terminate the traversal early if the condition is satisfied.

Parameters

visitor Visitor to call on each block.

Implements gem5::BaseTags.

Definition at line 194 of file compressed_tags.cc.

References blks.

◆ findVictim()

CacheBlk * gem5::CompressedTags::findVictim	(	Addr	addr,
		const bool	is_secure,
		const std::size_t	compressed_size,
		std::vector< CacheBlk * > &	evict_blks,
		const uint64_t	partition_id = 0 )

overridevirtual

Find replacement victim based on address.

Checks if data can be co- allocated before choosing blocks to be evicted.

Parameters

addr	Address to find a victim for.
is_secure	True if the target memory space is secure.
compressed_size	Size, in bits, of new block to allocate.
evict_blks	Cache blocks to be evicted.
partition_id	Partition ID for resource management.

Returns: Cache block to be replaced.

Implements gem5::BaseTags.

Definition at line 118 of file compressed_tags.cc.

References gem5::X86ISA::addr, gem5::SectorBlk::blks, gem5::SuperBlk::canCoAllocate(), DPRINTF, gem5::SectorTags::SectorTagsStats::evictionsReplacement, gem5::SectorTags::extractSectorOffset(), gem5::BaseTags::extractTag(), gem5::partitioning_policy::PartitionManager::filterByPartition(), gem5::BaseIndexingPolicy::getPossibleEntries(), gem5::replacement_policy::Base::getVictim(), gem5::BaseTags::indexingPolicy, gem5::SuperBlk::isCompressed(), gem5::CacheEntry::isValid(), gem5::TaggedEntry::matchTag(), gem5::ArmISA::offset, gem5::BaseTags::partitionManager, gem5::SuperBlk::print(), gem5::SectorTags::replacementPolicy, and gem5::SectorTags::sectorStats.

◆ tagsInit()

void gem5::CompressedTags::tagsInit ( )

overridevirtual

Member Data Documentation

◆ blks

std::vector<CompressionBlk> gem5::CompressedTags::blks

private

The cache blocks.

Definition at line 86 of file compressed_tags.hh.

Referenced by anyBlk(), and tagsInit().

◆ superBlks

std::vector<SuperBlk> gem5::CompressedTags::superBlks

private

The cache superblocks.

Definition at line 88 of file compressed_tags.hh.

Referenced by tagsInit().

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

mem/cache/tags/compressed_tags.hh
mem/cache/tags/compressed_tags.cc

Public Types

Public Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Member Typedef Documentation

◆ Params

Constructor & Destructor Documentation

◆ CompressedTags()

◆ ~CompressedTags()

Member Function Documentation

◆ anyBlk()

◆ findVictim()

◆ tagsInit()

Member Data Documentation

◆ blks

◆ superBlks