Miss Status and handling Register. More...

#include <mshr.hh>

Inheritance diagram for MSHR:

Classes
class	Target

class	TargetList

Public Types
typedef std::list< MSHR * >	List
	A list of MSHRs. More...

typedef List::iterator	Iterator
	MSHR list iterator. More...

Public Member Functions
bool	needsWritable () const
	The pending* and post* flags are only valid if inService is true. More...

bool	isCleaning () const

bool	isPendingModified () const

bool	hasPostInvalidate () const

bool	hasPostDowngrade () const

bool	sendPacket (BaseCache &cache) override
	Send this queue entry as a downstream packet, with the exact behaviour depending on the specific entry type. More...

bool	allocOnFill () const

bool	hasFromCache () const
	Determine if there are non-deferred requests from other caches. More...

bool	isWholeLineWrite () const
	Check if this MSHR contains only compatible writes, and if they span the entire cache line. More...

void	allocate (Addr blk_addr, unsigned blk_size, PacketPtr pkt, Tick when_ready, Counter _order, bool alloc_on_fill)
	Allocate a miss to this MSHR. More...

void	markInService (bool pending_modified_resp)

void	clearDownstreamPending ()

void	deallocate ()
	Mark this MSHR as free. More...

void	allocateTarget (PacketPtr target, Tick when, Counter order, bool alloc_on_fill)
	Add a request to the list of targets. More...

bool	handleSnoop (PacketPtr target, Counter order)

	MSHR ()
	A simple constructor. More...

int	getNumTargets () const
	Returns the current number of allocated targets. More...

TargetList	extractServiceableTargets (PacketPtr pkt)
	Extracts the subset of the targets that can be serviced given a received response. More...

bool	hasTargets () const
	Returns true if there are targets left. More...

QueueEntry::Target *	getTarget () override
	Returns a reference to the first target. More...

void	popTarget ()
	Pop first target. More...

bool	promoteDeferredTargets ()

void	promoteReadable ()
	Promotes deferred targets that do not require writable. More...

void	promoteWritable ()
	Promotes deferred targets that do not require writable. More...

bool	trySatisfyFunctional (PacketPtr pkt)

void	delay (Tick delay_ticks)
	Adds a delay relative to the current tick to the current MSHR. More...

void	print (std::ostream &os, int verbosity=0, const std::string &prefix="") const override
	Prints the contents of this MSHR for debugging. More...

std::string	print () const
	A no-args wrapper of print(std::ostream...) meant to be invoked from DPRINTFs avoiding string overheads in fast mode. More...

bool	matchBlockAddr (const Addr addr, const bool is_secure) const override
	Check if entry corresponds to the one being looked for. More...

bool	matchBlockAddr (const PacketPtr pkt) const override
	Check if entry contains a packet that corresponds to the one being looked for. More...

bool	conflictAddr (const QueueEntry *entry) const override
	Check if given entry's packets conflict with this' entries packets. More...

Public Member Functions inherited from QueueEntry
	QueueEntry ()

bool	isUncacheable () const

Public Member Functions inherited from Packet::SenderState
	SenderState ()

virtual	~SenderState ()

Public Member Functions inherited from Printable
	Printable ()

virtual	~Printable ()

Public Attributes
bool	wasWholeLineWrite
	Track if we sent this as a whole line write or not. More...

bool	isForward
	True if the entry is just a simple forward from an upper level. More...

Public Attributes inherited from QueueEntry
bool	inService
	True if the entry has been sent downstream. More...

Counter	order
	Order number assigned to disambiguate writes and misses. More...

Addr	blkAddr
	Block aligned address. More...

unsigned	blkSize
	Block size of the cache. More...

bool	isSecure
	True if the entry targets the secure memory space. More...

Public Attributes inherited from Packet::SenderState
SenderState *	predecessor

Private Member Functions
void	promoteIf (const std::function< bool(Target &)> &pred)
	Promotes deferred targets that satisfy a predicate. More...

Private Attributes
bool	downstreamPending
	Flag set by downstream caches. More...

bool	pendingModified
	Here we use one flag to track both if: More...

bool	postInvalidate
	Did we snoop an invalidate while waiting for data? More...

bool	postDowngrade
	Did we snoop a read while waiting for data? More...

Iterator	readyIter
	Pointer to this MSHR on the ready list. More...

Iterator	allocIter
	Pointer to this MSHR on the allocated list. More...

TargetList	targets
	List of all requests that match the address. More...

TargetList	deferredTargets

Friends
template<typename Entry >
class	Queue
	Consider the queues friends to avoid making everything public. More...

class	MSHRQueue

Additional Inherited Members
Protected Attributes inherited from QueueEntry
Tick	readyTime
	Tick when ready to issue. More...

bool	_isUncacheable
	True if the entry is uncacheable. More...

Detailed Description

Miss Status and handling Register.

This class keeps all the information needed to handle a cache miss including a list of target requests.

See also: gem5 Memory System

Definition at line 69 of file mshr.hh.

Member Typedef Documentation

◆ Iterator

typedef List::iterator MSHR::Iterator

MSHR list iterator.

Definition at line 303 of file mshr.hh.

◆ List

typedef std::list<MSHR *> MSHR::List

A list of MSHRs.

Definition at line 301 of file mshr.hh.

Constructor & Destructor Documentation

◆ MSHR()

MSHR::MSHR ( )

A simple constructor.

Definition at line 60 of file mshr.cc.

Member Function Documentation

◆ allocate()

void MSHR::allocate	(	Addr	blk_addr,
		unsigned	blk_size,
		PacketPtr	pkt,
		Tick	when_ready,
		Counter	_order,
		bool	alloc_on_fill
	)

Allocate a miss to this MSHR.

Parameters

blk_addr	The address of the block.
blk_size	The number of bytes to request.
pkt	The original miss.
when_ready	When should the MSHR be ready to act upon.
_order	The logical order of this MSHR
alloc_on_fill	Should the cache allocate a block on fill

Definition at line 294 of file mshr.cc.

References QueueEntry::_isUncacheable, MSHR::TargetList::add(), QueueEntry::blkAddr, QueueEntry::blkSize, Packet::cmd, deferredTargets, downstreamPending, MSHR::Target::FromCPU, MSHR::Target::FromPrefetcher, MemCmd::HardPFReq, MSHR::TargetList::init(), QueueEntry::inService, isForward, QueueEntry::isSecure, Packet::isSecure(), Packet::matchBlockAddr(), QueueEntry::order, QueueEntry::readyTime, Packet::req, targets, and wasWholeLineWrite.

Referenced by MSHRQueue::allocate().

◆ allocateTarget()

void MSHR::allocateTarget	(	PacketPtr	target,
		Tick	when,
		Counter	order,
		bool	alloc_on_fill
	)

Add a request to the list of targets.

Parameters

target The target.

Definition at line 367 of file mshr.cc.

References MSHR::TargetList::add(), Packet::cmd, deferredTargets, MSHR::Target::FromCPU, MemCmd::HardPFReq, hasPostDowngrade(), hasPostInvalidate(), QueueEntry::inService, isForward, isPendingModified(), Packet::needsWritable(), replaceUpgrade(), Packet::req, and targets.

Referenced by BaseCache::handleTimingReqMiss().

◆ allocOnFill()

bool MSHR::allocOnFill ( ) const

inline

Definition at line 332 of file mshr.hh.

References MSHR::TargetList::allocOnFill, and targets.

Referenced by print(), BaseCache::recvTimingResp(), and MSHR::TargetList::updateFlags().

◆ clearDownstreamPending()

void MSHR::clearDownstreamPending ( )

Definition at line 324 of file mshr.cc.

References MSHR::TargetList::clearDownstreamPending(), downstreamPending, and targets.

Referenced by MSHR::TargetList::clearDownstreamPending().

◆ conflictAddr()

bool MSHR::conflictAddr ( const QueueEntry * entry ) const

overridevirtual

Check if given entry's packets conflict with this' entries packets.

Parameters

entry Other entry to compare against.

Returns: True if entry matches given information.

Implements QueueEntry.

Definition at line 749 of file mshr.cc.

References QueueEntry::blkAddr, hasTargets(), QueueEntry::isSecure, and QueueEntry::matchBlockAddr().

◆ deallocate()

void MSHR::deallocate ( )

Mark this MSHR as free.

Definition at line 355 of file mshr.cc.

References deferredTargets, QueueEntry::inService, MSHR::TargetList::isReset(), MSHR::TargetList::resetFlags(), and targets.

◆ delay()

void MSHR::delay ( Tick delay_ticks )

inline

Adds a delay relative to the current tick to the current MSHR.

Parameters

delay_ticks the desired delay in ticks

Definition at line 490 of file mshr.hh.

References curTick(), and QueueEntry::readyTime.

Referenced by MSHRQueue::delay().

◆ extractServiceableTargets()

MSHR::TargetList MSHR::extractServiceableTargets ( PacketPtr pkt )

Extracts the subset of the targets that can be serviced given a received response.

This function returns the targets list unless the response is a ReadRespWithInvalidate. The ReadRespWithInvalidate is only invalidating response that its invalidation was not expected when the request (a ReadSharedReq) was sent out. For ReadRespWithInvalidate we can safely service only the first FromCPU target and all FromSnoop targets (inform all snoopers that we no longer have the block).

Parameters

pkt	The response from the downstream memory

Definition at line 536 of file mshr.cc.

References QueueEntry::blkAddr, QueueEntry::blkSize, Packet::cmd, MSHR::Target::FromCPU, MSHR::Target::FromPrefetcher, MSHR::Target::FromSnoop, MSHR::TargetList::init(), MSHR::TargetList::populateFlags(), MemCmd::ReadRespWithInvalidate, and targets.

Referenced by NoncoherentCache::serviceMSHRTargets(), and Cache::serviceMSHRTargets().

◆ getNumTargets()

int MSHR::getNumTargets ( ) const

inline

Returns the current number of allocated targets.

Returns: The current number of allocated targets.

Definition at line 422 of file mshr.hh.

References deferredTargets, and targets.

Referenced by MSHRQueue::allocate(), BaseCache::handleTimingReqMiss(), Cache::recvTimingSnoopReq(), and NoncoherentCache::serviceMSHRTargets().

◆ getTarget()

QueueEntry::Target* MSHR::getTarget ( )

inlineoverridevirtual

Returns a reference to the first target.

Returns: A pointer to the first target.

Implements QueueEntry.

Definition at line 449 of file mshr.hh.

References hasTargets(), and targets.

Referenced by BaseCache::recvTimingResp(), Cache::sendMSHRQueuePacket(), BaseCache::sendMSHRQueuePacket(), NoncoherentCache::serviceMSHRTargets(), and Cache::serviceMSHRTargets().

◆ handleSnoop()

bool MSHR::handleSnoop	(	PacketPtr	target,
		Counter	order
	)

◆ hasFromCache()

bool MSHR::hasFromCache ( ) const

inline

Determine if there are non-deferred requests from other caches.

Returns: true if any of the targets is from another cache

Definition at line 341 of file mshr.hh.

References MSHR::TargetList::hasFromCache, and targets.

Referenced by print(), and MSHR::TargetList::updateFlags().

◆ hasPostDowngrade()

bool MSHR::hasPostDowngrade ( ) const

inline

Definition at line 326 of file mshr.hh.

References QueueEntry::inService, and postDowngrade.

Referenced by allocateTarget(), promoteWritable(), and Cache::serviceMSHRTargets().

◆ hasPostInvalidate()

bool MSHR::hasPostInvalidate ( ) const

inline

Definition at line 322 of file mshr.hh.

References QueueEntry::inService, and postInvalidate.

Referenced by allocateTarget(), handleSnoop(), promoteReadable(), promoteWritable(), and Cache::serviceMSHRTargets().

◆ hasTargets()

bool MSHR::hasTargets ( ) const

inline

Returns true if there are targets left.

Returns: true if there are targets

Definition at line 443 of file mshr.hh.

References targets.

Referenced by conflictAddr(), MSHRQueue::forceDeallocateTarget(), getTarget(), and matchBlockAddr().

◆ isCleaning()

bool MSHR::isCleaning ( ) const

inline

Definition at line 313 of file mshr.hh.

References Packet::isClean(), and targets.

Referenced by BaseCache::handleEvictions().

◆ isPendingModified()

bool MSHR::isPendingModified ( ) const

inline

Definition at line 318 of file mshr.hh.

References QueueEntry::inService, and pendingModified.

Referenced by allocateTarget(), BaseCache::functionalAccess(), and handleSnoop().

◆ isWholeLineWrite()

bool MSHR::isWholeLineWrite ( ) const

inline

Check if this MSHR contains only compatible writes, and if they span the entire cache line.

This is used as part of the miss-packet creation. Note that new requests may arrive after a miss-packet has been created, and for the fill we therefore use the wasWholeLineWrite field.

Definition at line 382 of file mshr.hh.

References MSHR::TargetList::isWholeLineWrite(), and targets.

Referenced by markInService(), BaseCache::sendMSHRQueuePacket(), and MSHR::TargetList::updateWriteFlags().

◆ markInService()

void MSHR::markInService ( bool pending_modified_resp )

Definition at line 334 of file mshr.cc.

References MSHR::TargetList::clearDownstreamPending(), downstreamPending, QueueEntry::inService, isWholeLineWrite(), MSHR::TargetList::needsWritable, pendingModified, postDowngrade, postInvalidate, targets, and wasWholeLineWrite.

Referenced by MSHRQueue::markInService().

◆ matchBlockAddr() [1/2]

bool MSHR::matchBlockAddr	(	const Addr	addr,
		const bool	is_secure
	)		const

overridevirtual

Check if entry corresponds to the one being looked for.

Parameters

addr	Address to match against.
is_secure	Whether the target should be in secure space or not.

Returns: True if entry matches given information.

Implements QueueEntry.

Definition at line 735 of file mshr.cc.

References addr, QueueEntry::blkAddr, hasTargets(), and QueueEntry::isSecure.

◆ matchBlockAddr() [2/2]

bool MSHR::matchBlockAddr ( const PacketPtr pkt ) const

overridevirtual

Check if entry contains a packet that corresponds to the one being looked for.

Parameters

pkt	The packet to search for.

Returns: True if any of its targets' packets matches the given one.

Implements QueueEntry.

Definition at line 742 of file mshr.cc.

References QueueEntry::blkAddr, QueueEntry::blkSize, hasTargets(), QueueEntry::isSecure, and Packet::matchBlockAddr().

◆ needsWritable()

bool MSHR::needsWritable ( ) const

inline

The pending* and post* flags are only valid if inService is true.

Using the accessor functions lets us detect if these flags are accessed improperly. True if we need to get a writable copy of the block.

Definition at line 311 of file mshr.hh.

References MSHR::TargetList::needsWritable, and targets.

Referenced by BaseCache::handleEvictions(), print(), BaseCache::sendMSHRQueuePacket(), and MSHR::TargetList::updateFlags().

◆ popTarget()

void MSHR::popTarget ( )

inline

Pop first target.

Definition at line 458 of file mshr.hh.

References targets.

Referenced by MSHRQueue::forceDeallocateTarget().

◆ print() [1/2]

std::string MSHR::print ( ) const

A no-args wrapper of print(std::ostream...) meant to be invoked from DPRINTFs avoiding string overheads in fast mode.

Returns: string with mshr fields + [deferred]targets

Definition at line 727 of file mshr.cc.

◆ print() [2/2]

void MSHR::print	(	std::ostream &	os,
		int	verbosity = `0`,
		const std::string &	prefix = `""`
	)		const

overridevirtual

Prints the contents of this MSHR for debugging.

Implements Printable.

Definition at line 701 of file mshr.cc.

References QueueEntry::_isUncacheable, allocOnFill(), QueueEntry::blkAddr, QueueEntry::blkSize, ccprintf(), deferredTargets, downstreamPending, hasFromCache(), QueueEntry::inService, isForward, QueueEntry::isSecure, needsWritable(), X86ISA::os, postDowngrade, postInvalidate, MSHR::TargetList::print(), and targets.

Referenced by Cache::recvTimingSnoopReq().

◆ promoteDeferredTargets()

bool MSHR::promoteDeferredTargets ( )

Definition at line 570 of file mshr.cc.

References curTick(), deferredTargets, QueueEntry::order, MSHR::TargetList::populateFlags(), QueueEntry::readyTime, ArmISA::t, and targets.

Referenced by MSHRQueue::forceDeallocateTarget(), and BaseCache::recvTimingResp().

◆ promoteIf()

void MSHR::promoteIf ( const std::function< bool(Target &)> & pred )

private

Promotes deferred targets that satisfy a predicate.

Deferred targets are promoted to the target list if they satisfy a given condition. The operation stops at the first deferred target that doesn't satisfy the condition.

Parameters

pred	A condition on a Target

Definition at line 609 of file mshr.cc.

References MSHR::TargetList::clearDownstreamPending(), deferredTargets, downstreamPending, MSHR::TargetList::populateFlags(), and targets.

Referenced by promoteReadable(), and promoteWritable().

◆ promoteReadable()

void MSHR::promoteReadable ( )

Promotes deferred targets that do not require writable.

Move targets from the deferred targets list to the target list starting from the first deferred target until the first target that is a cache maintenance operation or needs a writable copy of the block

Definition at line 632 of file mshr.cc.

References deferredTargets, MSHR::Target::FromCPU, hasPostInvalidate(), promoteIf(), and ArmISA::t.

Referenced by BaseCache::recvTimingResp().

◆ promoteWritable()

void MSHR::promoteWritable ( )

Promotes deferred targets that do not require writable.

Requests in the deferred target list are moved to the target list up until the first target that is a cache maintenance operation or needs a writable copy of the block

Definition at line 653 of file mshr.cc.

References deferredTargets, MSHR::Target::FromCPU, hasPostDowngrade(), hasPostInvalidate(), MSHR::TargetList::needsWritable, promoteIf(), Packet::req, ArmISA::t, and targets.

Referenced by BaseCache::recvTimingResp().

◆ sendPacket()

bool MSHR::sendPacket ( BaseCache & cache )

overridevirtual

Send this queue entry as a downstream packet, with the exact behaviour depending on the specific entry type.

Implements QueueEntry.

Definition at line 695 of file mshr.cc.

References BaseCache::sendMSHRQueuePacket().

◆ trySatisfyFunctional()

bool MSHR::trySatisfyFunctional ( PacketPtr pkt )

Definition at line 680 of file mshr.cc.

References QueueEntry::blkAddr, QueueEntry::blkSize, deferredTargets, Packet::isPrint(), QueueEntry::isSecure, targets, MSHR::TargetList::trySatisfyFunctional(), and Packet::trySatisfyFunctional().

Friends And Related Function Documentation

◆ MSHRQueue

friend class MSHRQueue

friend

Definition at line 77 of file mshr.hh.

◆ Queue

template<typename Entry >

friend class Queue

friend

Consider the queues friends to avoid making everything public.

Definition at line 76 of file mshr.hh.

Member Data Documentation

◆ allocIter

Iterator MSHR::allocIter

private

Pointer to this MSHR on the allocated list.

See also: MissQueue, MSHRQueue::allocatedList

Definition at line 367 of file mshr.hh.

Referenced by MSHRQueue::allocate().

◆ deferredTargets

TargetList MSHR::deferredTargets

private

Definition at line 372 of file mshr.hh.

Referenced by allocate(), allocateTarget(), deallocate(), getNumTargets(), handleSnoop(), print(), promoteDeferredTargets(), promoteIf(), promoteReadable(), promoteWritable(), and trySatisfyFunctional().

◆ downstreamPending

bool MSHR::downstreamPending

private

Flag set by downstream caches.

Definition at line 82 of file mshr.hh.

Referenced by MSHR::TargetList::add(), allocate(), clearDownstreamPending(), handleSnoop(), markInService(), print(), and promoteIf().

◆ isForward

bool MSHR::isForward

True if the entry is just a simple forward from an upper level.

Definition at line 122 of file mshr.hh.

Referenced by allocate(), allocateTarget(), print(), BaseCache::recvTimingResp(), BaseCache::sendMSHRQueuePacket(), and Cache::serviceMSHRTargets().

◆ pendingModified

bool MSHR::pendingModified

private

Here we use one flag to track both if:

We are going to become owner or not, i.e., we will get the block in an ownership state (Owned or Modified) with BlkDirty set. This determines whether or not we are going to become the responder and ordering point for future requests that we snoop.
We know that we are going to get a writable block, i.e. we will get the block in writable state (Exclusive or Modified state) with BlkWritable set. That determines whether additional targets with needsWritable set will be able to be satisfied, or if not should be put on the deferred list to possibly wait for another request that does give us writable access.

Condition 2 is actually just a shortcut that saves us from possibly building a deferred target list and calling promoteWritable() every time we get a writable block. Condition 1, tracking ownership, is what is important. However, we never receive ownership without marking the block dirty, and consequently use pendingModified to track both ownership and writability rather than having separate pendingDirty and pendingWritable flags.

Definition at line 108 of file mshr.hh.

Referenced by isPendingModified(), and markInService().

◆ postDowngrade

bool MSHR::postDowngrade

private

Did we snoop a read while waiting for data?

Definition at line 114 of file mshr.hh.

Referenced by handleSnoop(), hasPostDowngrade(), markInService(), and print().

◆ postInvalidate

bool MSHR::postInvalidate

private

Did we snoop an invalidate while waiting for data?

Definition at line 111 of file mshr.hh.

Referenced by handleSnoop(), hasPostInvalidate(), markInService(), and print().

◆ readyIter

Iterator MSHR::readyIter

private

Pointer to this MSHR on the ready list.

See also: MissQueue, MSHRQueue::readyList

Definition at line 361 of file mshr.hh.

Referenced by MSHRQueue::allocate(), MSHRQueue::delay(), MSHRQueue::markInService(), MSHRQueue::markPending(), and MSHRQueue::moveToFront().

◆ targets

TargetList MSHR::targets

private

List of all requests that match the address.

Definition at line 370 of file mshr.hh.

Referenced by allocate(), allocateTarget(), allocOnFill(), clearDownstreamPending(), deallocate(), extractServiceableTargets(), getNumTargets(), getTarget(), handleSnoop(), hasFromCache(), hasTargets(), isCleaning(), isWholeLineWrite(), markInService(), needsWritable(), popTarget(), print(), promoteDeferredTargets(), promoteIf(), promoteWritable(), and trySatisfyFunctional().

◆ wasWholeLineWrite

bool MSHR::wasWholeLineWrite

Track if we sent this as a whole line write or not.

Definition at line 119 of file mshr.hh.

Referenced by allocate(), markInService(), BaseCache::recvTimingResp(), and Cache::serviceMSHRTargets().

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

mem/cache/mshr.hh
mem/cache/mshr.cc

Classes

Public Types

Public Member Functions

Public Attributes

Private Member Functions

Private Attributes

Friends

Additional Inherited Members

Detailed Description

Member Typedef Documentation

◆ Iterator

◆ List

Constructor & Destructor Documentation

◆ MSHR()

Member Function Documentation

◆ allocate()

◆ allocateTarget()

◆ allocOnFill()

◆ clearDownstreamPending()

◆ conflictAddr()

◆ deallocate()

◆ delay()

◆ extractServiceableTargets()

◆ getNumTargets()

◆ getTarget()

◆ handleSnoop()

◆ hasFromCache()

◆ hasPostDowngrade()

◆ hasPostInvalidate()

◆ hasTargets()

◆ isCleaning()

◆ isPendingModified()

◆ isWholeLineWrite()

◆ markInService()

◆ matchBlockAddr() [1/2]

◆ matchBlockAddr() [2/2]

◆ needsWritable()

◆ popTarget()

◆ print() [1/2]

◆ print() [2/2]

◆ promoteDeferredTargets()

◆ promoteIf()

◆ promoteReadable()

◆ promoteWritable()

◆ sendPacket()

◆ trySatisfyFunctional()

Friends And Related Function Documentation

◆ MSHRQueue

◆ Queue

Member Data Documentation

◆ allocIter

◆ deferredTargets

◆ downstreamPending

◆ isForward

◆ pendingModified

◆ postDowngrade

◆ postInvalidate

◆ readyIter

◆ targets

◆ wasWholeLineWrite