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

The write allocator inspects write packets and detects streaming patterns. More...

#include <base.hh>

Inheritance diagram for gem5::WriteAllocator:
gem5::SimObject gem5::EventManager gem5::Serializable gem5::Drainable gem5::statistics::Group gem5::Named

Public Member Functions

 WriteAllocator (const WriteAllocatorParams &p)
 
bool coalesce () const
 Should writes be coalesced? This is true if the mode is set to NO_ALLOCATE. More...
 
bool allocate () const
 Should writes allocate? More...
 
void reset ()
 Reset the write allocator state, meaning that it allocates for writes and has not recorded any information about qualifying writes that might trigger a switch to coalescing and later no allocation. More...
 
bool delay (Addr blk_addr)
 Access whether we need to delay the current write. More...
 
void resetDelay (Addr blk_addr)
 Clear delay counter for the input block. More...
 
void updateMode (Addr write_addr, unsigned write_size, Addr blk_addr)
 Update the write mode based on the current write packet. 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
 

Private Types

enum  WriteMode : char { WriteMode::ALLOCATE, WriteMode::COALESCE, WriteMode::NO_ALLOCATE }
 The current mode for write coalescing and allocation, either normal operation (ALLOCATE), write coalescing (COALESCE), or write coalescing without allocation (NO_ALLOCATE). More...
 

Private Attributes

WriteMode mode
 
Addr nextAddr
 Address to match writes against to detect streams. More...
 
uint32_t byteCount
 Bytes written contiguously. More...
 
const uint32_t coalesceLimit
 Limits for when to switch between the different write modes. More...
 
const uint32_t noAllocateLimit
 
const uint32_t delayThreshold
 The number of times the allocator will delay an WriteReq MSHR. More...
 
std::unordered_map< Addr, CounterdelayCtr
 Keep track of the number of times the allocator has delayed an WriteReq MSHR. More...
 

Additional Inherited Members

- Public Types inherited from gem5::SimObject
typedef SimObjectParams Params
 
- 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 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 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

The write allocator inspects write packets and detects streaming patterns.

The write allocator supports a single stream where writes are expected to access consecutive locations and keeps track of size of the area covered by the concecutive writes in byteCount.

1) When byteCount has surpassed the coallesceLimit the mode switches from ALLOCATE to COALESCE where writes should be delayed until the whole block is written at which point a single packet (whole line write) can service them.

2) When byteCount has also exceeded the noAllocateLimit (whole line) we switch to NO_ALLOCATE when writes should not allocate in the cache but rather send a whole line write to the memory below.

Definition at line 1369 of file base.hh.

Member Enumeration Documentation

◆ WriteMode

enum gem5::WriteAllocator::WriteMode : char
strongprivate

The current mode for write coalescing and allocation, either normal operation (ALLOCATE), write coalescing (COALESCE), or write coalescing without allocation (NO_ALLOCATE).

Enumerator
ALLOCATE 
COALESCE 
NO_ALLOCATE 

Definition at line 1454 of file base.hh.

Constructor & Destructor Documentation

◆ WriteAllocator()

gem5::WriteAllocator::WriteAllocator ( const WriteAllocatorParams &  p)
inline

Definition at line 1372 of file base.hh.

References reset().

Member Function Documentation

◆ allocate()

bool gem5::WriteAllocator::allocate ( ) const
inline

Should writes allocate?

Returns
return true if the cache should not allocate for writes.

Definition at line 1396 of file base.hh.

References mode, and NO_ALLOCATE.

Referenced by gem5::Cache::handleAtomicReqMiss(), and gem5::BaseCache::recvTimingResp().

◆ coalesce()

bool gem5::WriteAllocator::coalesce ( ) const
inline

Should writes be coalesced? This is true if the mode is set to NO_ALLOCATE.

Returns
return true if the cache should coalesce writes.

Definition at line 1387 of file base.hh.

References ALLOCATE, and mode.

Referenced by gem5::BaseCache::coalesce(), and gem5::BaseCache::sendMSHRQueuePacket().

◆ delay()

bool gem5::WriteAllocator::delay ( Addr  blk_addr)
inline

Access whether we need to delay the current write.

Parameters
blk_addrThe block address the packet writes to
Returns
true if the current packet should be delayed

Definition at line 1418 of file base.hh.

References delayCtr.

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

◆ reset()

void gem5::WriteAllocator::reset ( )
inline

Reset the write allocator state, meaning that it allocates for writes and has not recorded any information about qualifying writes that might trigger a switch to coalescing and later no allocation.

Definition at line 1406 of file base.hh.

References ALLOCATE, byteCount, mode, and nextAddr.

Referenced by gem5::BaseCache::sendMSHRQueuePacket(), and WriteAllocator().

◆ resetDelay()

void gem5::WriteAllocator::resetDelay ( Addr  blk_addr)
inline

Clear delay counter for the input block.

Parameters
blk_addrThe accessed cache block

Definition at line 1432 of file base.hh.

References delayCtr.

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

◆ updateMode()

void gem5::WriteAllocator::updateMode ( Addr  write_addr,
unsigned  write_size,
Addr  blk_addr 
)

Update the write mode based on the current write packet.

This method compares the packet's address with any current stream, and updates the tracking and the mode accordingly.

Parameters
write_addrStart address of the write request
write_sizeSize of the write request
blk_addrThe block address that this packet writes to

Definition at line 2595 of file base.cc.

References DPRINTF, and gem5::ArmISA::mode.

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

Member Data Documentation

◆ byteCount

uint32_t gem5::WriteAllocator::byteCount
private

Bytes written contiguously.

Saturating once we no longer allocate.

Definition at line 1469 of file base.hh.

Referenced by reset().

◆ coalesceLimit

const uint32_t gem5::WriteAllocator::coalesceLimit
private

Limits for when to switch between the different write modes.

Definition at line 1474 of file base.hh.

◆ delayCtr

std::unordered_map<Addr, Counter> gem5::WriteAllocator::delayCtr
private

Keep track of the number of times the allocator has delayed an WriteReq MSHR.

Definition at line 1485 of file base.hh.

Referenced by delay(), and resetDelay().

◆ delayThreshold

const uint32_t gem5::WriteAllocator::delayThreshold
private

The number of times the allocator will delay an WriteReq MSHR.

Definition at line 1479 of file base.hh.

◆ mode

WriteMode gem5::WriteAllocator::mode
private

Definition at line 1460 of file base.hh.

Referenced by allocate(), coalesce(), and reset().

◆ nextAddr

Addr gem5::WriteAllocator::nextAddr
private

Address to match writes against to detect streams.

Definition at line 1463 of file base.hh.

Referenced by reset().

◆ noAllocateLimit

const uint32_t gem5::WriteAllocator::noAllocateLimit
private

Definition at line 1475 of file base.hh.


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

Generated on Tue Sep 21 2021 12:28:25 for gem5 by doxygen 1.8.17