Class used for synchronizing the simulation events to a real-time "wall clock" using Posix Clock functions. More...

#include <wall-clock-synchronizer.h>

Inheritance diagram for ns3::WallClockSynchronizer:

Static Public Attributes
static const uint64_t	NS_PER_SEC = (uint64_t)1000000000

static const uint64_t	US_PER_NS = (uint64_t)1000

static const uint64_t	US_PER_SEC = (uint64_t)1000000

Protected Member Functions
virtual uint64_t	DoEventEnd (void)

virtual void	DoEventStart (void)

virtual uint64_t	DoGetCurrentRealtime (void)
	Retrieve the value of the origin of the underlying normalized wall clock time in nanosecond units. More...

virtual int64_t	DoGetDrift (uint64_t ns)
	Declaration of method used to retrieve drift between the real time clock used to synchronize the simulation and the current simulation time. More...

virtual bool	DoRealtime (void)
	Return true if this synchronizer is actually synchronizing to a realtime clock. The simulator sometimes needs to know this. More...

virtual void	DoSetCondition (bool cond)
	Declaration of the method used to set the condition variable that tells a possible simulator thread waiting in the Synchronize method that an event has happened which demands a reevaluation of the wait time. More...

virtual void	DoSetOrigin (uint64_t ns)
	Establish a correspondence between a simulation time and a wall-clock (real) time. More...

virtual void	DoSignal (void)
	Declaration of the method used to tell a possible simulator thread waiting in the DoSynchronize method that an event has happened which demands a reevaluation of the wait time. More...

virtual bool	DoSynchronize (uint64_t nsCurrent, uint64_t nsDelay)
	Wait until the real time is in sync with the specified simulation time. More...

uint64_t	DriftCorrect (uint64_t nsNow, uint64_t nsDelay)

uint64_t	GetNormalizedRealtime (void)

uint64_t	GetRealtime (void)

void	NsToTimeval (int64_t ns, struct timeval *tv)

bool	SleepWait (uint64_t)

bool	SpinWait (uint64_t)

void	TimevalAdd (struct timeval tv1, struct timeval tv2, struct timeval *result)

uint64_t	TimevalToNs (struct timeval *tv)

Protected Member Functions inherited from ns3::Object
	Object (const Object &o)

virtual void	DoDispose (void)

virtual void	DoInitialize (void)

virtual void	NotifyNewAggregate (void)

Protected Member Functions inherited from ns3::ObjectBase
void	ConstructSelf (const AttributeConstructionList &attributes)

virtual void	NotifyConstructionCompleted (void)

Protected Attributes
SystemCondition	m_condition

uint64_t	m_cpuTick

uint64_t	m_jiffy

uint64_t	m_nsEventStart

uint64_t	m_realtimeTick

Protected Attributes inherited from ns3::Synchronizer
uint64_t	m_realtimeOriginNano

uint64_t	m_simOriginNano

Additional Inherited Members
Public Member Functions inherited from ns3::Synchronizer
uint64_t	EventEnd (void)
	Ask the synchronizer to return the time step between the instant remembered during EventStart and now. Used in conjunction with EventStart to determine the real execution time of a simulation event. More...

void	EventStart (void)
	Ask the synchronizer to remember what time it is. Typically used with EventEnd to determine the real execution time of a simulation event. More...

uint64_t	GetCurrentRealtime (void)
	Retrieve the value of the origin of the underlying normalized wall clock time in simulator timestep units. More...

int64_t	GetDrift (uint64_t ts)
	Retrieve the difference between the real time clock used to synchronize the simulation and the simulation time (in simulator timestep units). More...

uint64_t	GetOrigin (void)
	Retrieve the value of the origin of the simulation time in simulator timestep units. More...

bool	Realtime (void)
	Return true if this synchronizer is actually synchronizing to a realtime clock. The simulator sometimes needs to know this. More...

void	SetCondition (bool)
	Set the condition variable that tells a possible simulator thread waiting in the Synchronize method that an event has happened which demands a reevaluation of the wait time. More...

void	SetOrigin (uint64_t ts)
	Establish a correspondence between a simulation time and the synchronizer real time. More...

void	Signal (void)
	Tell a possible simulator thread waiting in the Synchronize method that an event has happened which demands a reevaluation of the wait time. This will cause the thread to wake and return to the simulator proper where it can get its bearings. More...

bool	Synchronize (uint64_t tsCurrent, uint64_t tsDelay)
	Wait until the real time is in sync with the specified simulation time or until the synchronizer is Sigalled. More...

Public Member Functions inherited from ns3::Object
void	AggregateObject (Ptr< Object > other)

void	Dispose (void)

AggregateIterator	GetAggregateIterator (void) const

virtual TypeId	GetInstanceTypeId (void) const

template<typename T >
Ptr< T >	GetObject (void) const

template<typename T >
Ptr< T >	GetObject (TypeId tid) const

void	Initialize (void)

Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
	SimpleRefCount (const SimpleRefCount &o)

uint32_t	GetReferenceCount (void) const

SimpleRefCount &	operator= (const SimpleRefCount &o)

void	Ref (void) const

void	Unref (void) const

Public Member Functions inherited from ns3::ObjectBase
void	GetAttribute (std::string name, AttributeValue &value) const

bool	GetAttributeFailSafe (std::string name, AttributeValue &attribute) const

void	SetAttribute (std::string name, const AttributeValue &value)

bool	SetAttributeFailSafe (std::string name, const AttributeValue &value)

bool	TraceConnect (std::string name, std::string context, const CallbackBase &cb)

bool	TraceConnectWithoutContext (std::string name, const CallbackBase &cb)

bool	TraceDisconnect (std::string name, std::string context, const CallbackBase &cb)

bool	TraceDisconnectWithoutContext (std::string name, const CallbackBase &cb)

Static Public Member Functions inherited from ns3::Synchronizer
static TypeId	GetTypeId (void)

Static Public Member Functions inherited from ns3::Object
static TypeId	GetTypeId (void)

Static Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
static void	Cleanup (void)

Static Public Member Functions inherited from ns3::ObjectBase
static TypeId	GetTypeId (void)

Detailed Description

Class used for synchronizing the simulation events to a real-time "wall clock" using Posix Clock functions.

Enable this synchronizer using:

DefaultValue::Bind ("Synchronizer", "WallClockSynchronizer");

before calling any simulator functions.

The simulation clock is maintained as a 64-bit integer in a unit specified by the user through the TimeStepPrecision::Set function. This means that it is not possible to specify event expiration times with anything better than this user-specified accuracy.

There are a couple of more issues at this level. Posix clocks provide access to several clocks we could use as a wall clock. We don't care about time in the sense of 0430 CEST, we care about some piece of hardware that ticks at some regular period. The most accurate posix clock in this respect is the CLOCK_PROCESS_CPUTIME_ID clock. This is a high-resolution register in the CPU. For example, on Intel machines this corresponds to the timestamp counter (TSC) register. The resolution of this counter will be on the order of nanoseconds.

Now, just because we can measure time in nanoseconds doesn't mean we can put our process to sleep to nanosecond resolution. We are eventually going to use the function clock_nanosleep () to sleep until a simulation Time specified by the caller.

MORE ON JIFFIES, SLEEP, PROCESSES, etc., as required

Nanosleep takes a struct timespec as an input so we have to deal with conversion between Time and struct timespec here. They are both interpreted as elapsed times.

Definition at line 62 of file wall-clock-synchronizer.h.

Member Function Documentation

uint64_t ns3::WallClockSynchronizer::DoGetCurrentRealtime ( void )

protectedvirtual

Retrieve the value of the origin of the underlying normalized wall clock time in nanosecond units.

Subclasses are expected to implement this method to do the actual real-time-clock-specific work of getting the current time.

Returns: The normalized wall clock time (in nanosecond units).

See Also: TimeStepPrecision::Get; Synchronizer::SetOrigin

Implements ns3::Synchronizer.

Definition at line 84 of file wall-clock-synchronizer.cc.

References NS_LOG_FUNCTION.

int64_t ns3::WallClockSynchronizer::DoGetDrift ( uint64_t ns )

protectedvirtual

Declaration of method used to retrieve drift between the real time clock used to synchronize the simulation and the current simulation time.

Parameters

ns	Simulation timestep from the simulator normalized to nanosecond steps.

Returns: Drift in nanosecond units.

See Also: TimeStepPrecision::Get; Synchronizer::SetOrigin; Synchronizer::GetDrift

Implements ns3::Synchronizer.

Definition at line 107 of file wall-clock-synchronizer.cc.

References NS_LOG_FUNCTION.

Referenced by DoSynchronize().

bool ns3::WallClockSynchronizer::DoRealtime ( void )

protectedvirtual

Return true if this synchronizer is actually synchronizing to a realtime clock. The simulator sometimes needs to know this.

Subclasses are expected to implement this method to tell the outside world whether or not they are synchronizing to a realtime clock.

Returns: True if locked with realtime, false if not.

Implements ns3::Synchronizer.

Definition at line 77 of file wall-clock-synchronizer.cc.

References NS_LOG_FUNCTION.

void ns3::WallClockSynchronizer::DoSetCondition ( bool )

protectedvirtual

Declaration of the method used to set the condition variable that tells a possible simulator thread waiting in the Synchronize method that an event has happened which demands a reevaluation of the wait time.

See Also: Synchronizer::SetCondition

Implements ns3::Synchronizer.

Definition at line 274 of file wall-clock-synchronizer.cc.

References NS_LOG_FUNCTION, and ns3::SystemCondition::SetCondition().

void ns3::WallClockSynchronizer::DoSetOrigin ( uint64_t ns )

protectedvirtual

Establish a correspondence between a simulation time and a wall-clock (real) time.

There are three timelines involved here: the simulation time, the (absolute) wall-clock time and the (relative) synchronizer real time. Calling this method makes a correspondence between the origin of the synchronizer time and the current wall-clock time.

This method is expected to be called at the "instant" before simulation begins. At this point, simulation time = 0, and synchronizer time is set = 0 in this method. We then associate this time with the current value of the real time clock that will be used to actually perform the synchronization.

Subclasses are expected to implement this method to do the actual real-time-clock-specific work of making the correspondence mentioned above. for example, this is where the differences between Time parameters and parameters to clock_nanosleep would be dealt with.

Parameters

ns	The simulation time we need to use as the origin (normalized to nanosecond units).

Implements ns3::Synchronizer.

Definition at line 91 of file wall-clock-synchronizer.cc.

References NS_LOG_FUNCTION, and NS_LOG_INFO.

void ns3::WallClockSynchronizer::DoSignal ( void )

protectedvirtual

Declaration of the method used to tell a possible simulator thread waiting in the DoSynchronize method that an event has happened which demands a reevaluation of the wait time.

See Also: Synchronizer::Signal

Implements ns3::Synchronizer.

Definition at line 265 of file wall-clock-synchronizer.cc.

References NS_LOG_FUNCTION, ns3::SystemCondition::SetCondition(), and ns3::SystemCondition::Signal().

bool ns3::WallClockSynchronizer::DoSynchronize	(	uint64_t	nsCurrent,
		uint64_t	nsDelay
	)

protectedvirtual

Wait until the real time is in sync with the specified simulation time.

This is where the real work of synchronization is done. The Time passed in as a parameter is the simulation time. The job of Synchronize is to translate from simulation time to synchronizer time (in a perfect world this is the same time) and then figure out how long in real-time it needs to wait until that synchronizer / simulation time comes around.

Subclasses are expected to implement this method to do the actual real-time-clock-specific work of waiting (either busy-waiting or sleeping, or some combination) until the requested simulation time.

Parameters

ns	The simulation time we need to wait for (normalized to nanosecond units).

See Also: TimeStepPrecision::Get

Implements ns3::Synchronizer.

Definition at line 147 of file wall-clock-synchronizer.cc.

References DoGetDrift(), NS_LOG_FUNCTION, and NS_LOG_INFO.

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

src/core/model/wall-clock-synchronizer.h
src/core/model/wall-clock-synchronizer.cc

Static Public Attributes

Protected Member Functions

Protected Attributes

Additional Inherited Members

Detailed Description

Member Function Documentation