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	isPendingModified () const

bool	hasPostInvalidate () const

bool	hasPostDowngrade () const

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

bool	allocOnFill () const

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...

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

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

bool	promoteDeferredTargets ()

void	promoteWritable ()

bool	checkFunctional (PacketPtr pkt)

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

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	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 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 63 of file mshr.hh.

Member Typedef Documentation

typedef List::iterator MSHR::Iterator

MSHR list iterator.

Definition at line 228 of file mshr.hh.

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

A list of MSHRs.

Definition at line 226 of file mshr.hh.

Constructor & Destructor Documentation

MSHR::MSHR ( )

A simple constructor.

Definition at line 65 of file mshr.cc.

Member Function Documentation

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 240 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, QueueEntry::inService, isForward, MSHR::TargetList::isReset(), QueueEntry::isSecure, Packet::isSecure(), Request::isUncacheable(), QueueEntry::order, QueueEntry::readyTime, Packet::req, and targets.

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 303 of file mshr.cc.

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

Referenced by Cache::recvTimingReq().

bool MSHR::allocOnFill ( ) const

inline

Definition at line 252 of file mshr.hh.

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

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

bool MSHR::checkFunctional ( PacketPtr pkt )

Definition at line 543 of file mshr.cc.

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

void MSHR::clearDownstreamPending ( )

Definition at line 264 of file mshr.cc.

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

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

void MSHR::deallocate ( )

Mark this MSHR as free.

Definition at line 291 of file mshr.cc.

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

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 458 of file mshr.cc.

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

Referenced by Cache::recvTimingResp().

int MSHR::getNumTargets ( ) const

inline

Returns the current number of allocated targets.

Returns: The current number of allocated targets.

Definition at line 312 of file mshr.hh.

References deferredTargets, and targets.

Referenced by Cache::recvTimingReq(), and Cache::recvTimingSnoopReq().

Target* MSHR::getTarget ( )

inline

Returns a reference to the first target.

Returns: A pointer to the first target.

Definition at line 339 of file mshr.hh.

References hasTargets(), and targets.

Referenced by Cache::recvTimingResp(), and Cache::sendMSHRQueuePacket().

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

bool MSHR::hasPostDowngrade ( ) const

inline

Definition at line 246 of file mshr.hh.

References QueueEntry::inService, and postDowngrade.

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

bool MSHR::hasPostInvalidate ( ) const

inline

Definition at line 242 of file mshr.hh.

References QueueEntry::inService, and postInvalidate.

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

bool MSHR::hasTargets ( ) const

inline

Returns true if there are targets left.

Returns: true if there are targets

Definition at line 333 of file mshr.hh.

References targets.

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

bool MSHR::isPendingModified ( ) const

inline

Definition at line 238 of file mshr.hh.

References QueueEntry::inService, and pendingModified.

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

void MSHR::markInService ( bool pending_modified_resp )

Definition at line 274 of file mshr.cc.

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

Referenced by MSHRQueue::markInService().

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 236 of file mshr.hh.

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

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

void MSHR::popTarget ( )

inline

Pop first target.

Definition at line 348 of file mshr.hh.

References targets.

Referenced by MSHRQueue::forceDeallocateTarget().

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

virtual

Prints the contents of this MSHR for debugging.

Implements Printable.

Definition at line 564 of file mshr.cc.

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

Referenced by Cache::recvTimingSnoopReq().

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 589 of file mshr.cc.

bool MSHR::promoteDeferredTargets ( )

Definition at line 491 of file mshr.cc.

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

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

void MSHR::promoteWritable ( )

Definition at line 518 of file mshr.cc.

References MSHR::TargetList::clearDownstreamPending(), deferredTargets, downstreamPending, hasPostDowngrade(), hasPostInvalidate(), MSHR::TargetList::needsWritable, MSHR::TargetList::resetFlags(), and targets.

Referenced by Cache::recvTimingResp().

bool MSHR::sendPacket ( Cache & cache )

virtual

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

Implements QueueEntry.

Definition at line 558 of file mshr.cc.

References Cache::sendMSHRQueuePacket().

Friends And Related Function Documentation

friend class MSHRQueue

friend

Definition at line 71 of file mshr.hh.

template<typename Entry >

friend class Queue

friend

Consider the queues friends to avoid making everything public.

Definition at line 70 of file mshr.hh.

Member Data Documentation

Iterator MSHR::allocIter

private

Pointer to this MSHR on the allocated list.

See Also: MissQueue, MSHRQueue::allocatedList

Definition at line 267 of file mshr.hh.

TargetList MSHR::deferredTargets

private

Definition at line 272 of file mshr.hh.

Referenced by allocate(), allocateTarget(), checkFunctional(), deallocate(), getNumTargets(), handleSnoop(), print(), promoteDeferredTargets(), and promoteWritable().

bool MSHR::downstreamPending

private

Flag set by downstream caches.

Definition at line 76 of file mshr.hh.

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

bool MSHR::isForward

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

Definition at line 113 of file mshr.hh.

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

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 102 of file mshr.hh.

Referenced by isPendingModified(), and markInService().

bool MSHR::postDowngrade

private

Did we snoop a read while waiting for data?

Definition at line 108 of file mshr.hh.

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

bool MSHR::postInvalidate

private

Did we snoop an invalidate while waiting for data?

Definition at line 105 of file mshr.hh.

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