gem5  v21.1.0.2
Public Types | Public Member Functions | Private Attributes | List of all members
gem5::CompressedTags Class Reference

A CompressedTags cache tag store. More...

#include <compressed_tags.hh>

Inheritance diagram for gem5::CompressedTags:
gem5::SectorTags gem5::BaseTags gem5::ClockedObject gem5::SimObject gem5::Clocked gem5::EventManager gem5::Serializable gem5::Drainable gem5::statistics::Group gem5::Named

Public Types

typedef CompressedTagsParams Params
 Convenience typedef. More...
 
- Public Types inherited from gem5::SectorTags
typedef SectorTagsParams Params
 Convenience typedef. More...
 
- Public Types inherited from gem5::BaseTags
typedef BaseTagsParams Params
 
- Public Types inherited from gem5::ClockedObject
using Params = ClockedObjectParams
 Parameters of ClockedObject. More...
 
- Public Types inherited from gem5::SimObject
typedef SimObjectParams Params
 

Public Member Functions

 CompressedTags (const Params &p)
 Construct and initialize this tag store. More...
 
virtual ~CompressedTags ()
 Destructor. More...
 
void tagsInit () override
 Initialize blocks as SuperBlk and CompressionBlk instances. More...
 
CacheBlkfindVictim (Addr addr, const bool is_secure, const std::size_t compressed_size, std::vector< CacheBlk * > &evict_blks) override
 Find replacement victim based on address. More...
 
void forEachBlk (std::function< void(CacheBlk &)> visitor) override
 Visit each sub-block in the tags and apply a visitor. More...
 
bool anyBlk (std::function< bool(CacheBlk &)> visitor) override
 Find if any of the sub-blocks satisfies a condition. More...
 
- Public Member Functions inherited from gem5::SectorTags
 SectorTags (const Params &p)
 Construct and initialize this tag store. More...
 
virtual ~SectorTags ()
 Destructor. More...
 
void tagsInit () override
 Initialize blocks as SectorBlk and SectorSubBlk instances. More...
 
void invalidate (CacheBlk *blk) override
 This function updates the tags when a block is invalidated but does not invalidate the block itself. More...
 
CacheBlkaccessBlock (const PacketPtr pkt, Cycles &lat) override
 Access block and update replacement data. More...
 
void insertBlock (const PacketPtr pkt, CacheBlk *blk) override
 Insert the new block into the cache and update replacement data. More...
 
void moveBlock (CacheBlk *src_blk, CacheBlk *dest_blk) override
 Move a block's metadata to another location decided by the replacement policy. More...
 
CacheBlkfindBlock (Addr addr, bool is_secure) const override
 Finds the given address in the cache, do not update replacement data. More...
 
CacheBlkfindVictim (Addr addr, const bool is_secure, const std::size_t size, std::vector< CacheBlk * > &evict_blks) override
 Find replacement victim based on address. More...
 
int extractSectorOffset (Addr addr) const
 Calculate a block's offset in a sector from the address. More...
 
Addr regenerateBlkAddr (const CacheBlk *blk) const override
 Regenerate the block address from the tag and location. More...
 
void forEachBlk (std::function< void(CacheBlk &)> visitor) override
 Visit each sub-block in the tags and apply a visitor. More...
 
bool anyBlk (std::function< bool(CacheBlk &)> visitor) override
 Find if any of the sub-blocks satisfies a condition. More...
 
- Public Member Functions inherited from gem5::BaseTags
 BaseTags (const Params &p)
 
virtual ~BaseTags ()
 Destructor. More...
 
void cleanupRefs ()
 Average in the reference count for valid blocks when the simulation exits. More...
 
void computeStats ()
 Computes stats just prior to dump event. More...
 
std::string print ()
 Print all tags used. More...
 
virtual ReplaceableEntryfindBlockBySetAndWay (int set, int way) const
 Find a block given set and way. More...
 
Addr blkAlign (Addr addr) const
 Align an address to the block size. More...
 
int extractBlkOffset (Addr addr) const
 Calculate the block offset of an address. More...
 
virtual void setWayAllocationMax (int ways)
 Limit the allocation for the cache ways. More...
 
virtual int getWayAllocationMax () const
 Get the way allocation mask limit. More...
 
virtual Addr extractTag (const Addr addr) const
 Generate the tag from the given address. More...
 
- Public Member Functions inherited from gem5::ClockedObject
 ClockedObject (const ClockedObjectParams &p)
 
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::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
 
- Public Member Functions inherited from gem5::Clocked
void updateClockPeriod ()
 Update the tick to the current tick. More...
 
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. More...
 
Cycles curCycle () const
 Determine the current cycle, corresponding to a tick aligned to a clock edge. More...
 
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. More...
 
uint64_t frequency () const
 
Tick clockPeriod () const
 
double voltage () const
 
Cycles ticksToCycles (Tick t) const
 
Tick cyclesToTicks (Cycles c) const
 

Private Attributes

std::vector< CompressionBlkblks
 The cache blocks. More...
 
std::vector< SuperBlksuperBlks
 The cache superblocks. More...
 

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. 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...
 
- Public Attributes inherited from gem5::ClockedObject
PowerStatepowerState
 
- 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 Member Functions inherited from gem5::Clocked
 Clocked (ClockDomain &clk_domain)
 Create a clocked object and set the clock domain based on the parameters. More...
 
 Clocked (Clocked &)=delete
 
Clockedoperator= (Clocked &)=delete
 
virtual ~Clocked ()
 Virtual destructor due to inheritance. More...
 
void resetClock () const
 Reset the object's clock using the current global tick value. More...
 
virtual void clockPeriodUpdated ()
 A hook subclasses can implement so they can do any extra work that's needed when the clock rate is changed. More...
 
- Protected Attributes inherited from gem5::SectorTags
unsigned allocAssoc
 The allocatable associativity of the cache (alloc mask). More...
 
const bool sequentialAccess
 Whether tags and data are accessed sequentially. More...
 
replacement_policy::BasereplacementPolicy
 Replacement policy. More...
 
const unsigned numBlocksPerSector
 Number of data blocks per sector. More...
 
const unsigned numSectors
 The number of sectors in the cache. More...
 
const int sectorShift
 The amount to shift the address to get the sector tag. More...
 
const unsigned sectorMask
 Mask out all bits that aren't part of the sector tag. More...
 
gem5::SectorTags::SectorTagsStats sectorStats
 
- Protected Attributes inherited from gem5::BaseTags
const unsigned blkSize
 The block size of the cache. More...
 
const Addr blkMask
 Mask out all bits that aren't part of the block offset. More...
 
const unsigned size
 The size of the cache. More...
 
const Cycles lookupLatency
 The tag lookup latency of the cache. More...
 
Systemsystem
 System we are currently operating in. More...
 
BaseIndexingPolicyindexingPolicy
 Indexing policy. More...
 
const unsigned warmupBound
 The number of tags that need to be touched to meet the warmup percentage. More...
 
bool warmedUp
 Marked true when the cache is warmed up. More...
 
const unsigned numBlocks
 the number of blocks in the cache More...
 
std::unique_ptr< uint8_t[]> dataBlks
 The data blocks, 1 per cache block. More...
 
gem5::BaseTags::BaseTagStats 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...
 

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 70 of file compressed_tags.hh.

Member Typedef Documentation

◆ Params

typedef CompressedTagsParams gem5::CompressedTags::Params

Convenience typedef.

Definition at line 80 of file compressed_tags.hh.

Constructor & Destructor Documentation

◆ CompressedTags()

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

Construct and initialize this tag store.

Definition at line 47 of file compressed_tags.cc.

◆ ~CompressedTags()

virtual gem5::CompressedTags::~CompressedTags ( )
inlinevirtual

Destructor.

Definition at line 90 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
visitorVisitor to call on each block.

Implements gem5::BaseTags.

Definition at line 175 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 
)
overridevirtual

Find replacement victim based on address.

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

Parameters
addrAddress to find a victim for.
is_secureTrue if the target memory space is secure.
compressed_sizeSize, in bits, of new block to allocate.
evict_blksCache blocks to be evicted.
Returns
Cache block to be replaced.

Implements gem5::BaseTags.

Definition at line 105 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::BaseIndexingPolicy::getPossibleEntries(), gem5::replacement_policy::Base::getVictim(), gem5::BaseTags::indexingPolicy, gem5::SuperBlk::isCompressed(), gem5::TaggedEntry::isValid(), gem5::TaggedEntry::matchTag(), gem5::ArmISA::offset, gem5::SuperBlk::print(), gem5::SectorTags::replacementPolicy, and gem5::SectorTags::sectorStats.

◆ forEachBlk()

void gem5::CompressedTags::forEachBlk ( std::function< void(CacheBlk &)>  visitor)
overridevirtual

Visit each sub-block in the tags and apply a visitor.

The visitor should be a std::function that takes a cache block. reference as its parameter.

Parameters
visitorVisitor to call on each block.

Implements gem5::BaseTags.

Definition at line 167 of file compressed_tags.cc.

References blks.

◆ tagsInit()

void gem5::CompressedTags::tagsInit ( )
overridevirtual

Member Data Documentation

◆ blks

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

The cache blocks.

Definition at line 74 of file compressed_tags.hh.

Referenced by anyBlk(), forEachBlk(), and tagsInit().

◆ superBlks

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

The cache superblocks.

Definition at line 76 of file compressed_tags.hh.

Referenced by tagsInit().


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

Generated on Tue Sep 21 2021 12:27:24 for gem5 by doxygen 1.8.17