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ns3::WallClockSynchronizer Class Reference

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:
+ Collaboration diagram for ns3::WallClockSynchronizer:

Public Member Functions

 WallClockSynchronizer ()
 
virtual ~WallClockSynchronizer ()
 
- Public Member Functions inherited from ns3::Synchronizer
 Synchronizer ()
 
virtual ~Synchronizer ()
 
uint64_t EventEnd (void)
 Ask the synchronizer to return the time step between the instant remembered during EventStart and now. More...
 
void EventStart (void)
 Ask the synchronizer to remember what time it is. 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. 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. 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
 Object ()
 
virtual ~Object ()
 
void AggregateObject (Ptr< Object > other)
 
void Dispose (void)
 Run the DoDispose methods of this object and all the objects aggregated to it. More...
 
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)
 This method calls the virtual DoInitialize method on all the objects aggregated to this object. More...
 
- Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
 SimpleRefCount ()
 Constructor. More...
 
 SimpleRefCount (const SimpleRefCount &o)
 Copy constructor. More...
 
uint32_t GetReferenceCount (void) const
 Get the reference count of the object. More...
 
SimpleRefCountoperator= (const SimpleRefCount &o)
 Assignment. More...
 
void Ref (void) const
 Increment the reference count. More...
 
void Unref (void) const
 Decrement the reference count. More...
 
- Public Member Functions inherited from ns3::ObjectBase
virtual ~ObjectBase ()
 Virtual destructor. More...
 
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 Attributes

static const uint64_t NS_PER_SEC = (uint64_t)1000000000
 Conversion from ns to s. More...
 
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. 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)
 This method is called by Object::Dispose or by the object's destructor, whichever comes first. More...
 
virtual void DoInitialize (void)
 This method is called only once by Object::Initialize. More...
 
virtual void NotifyNewAggregate (void)
 This method is invoked whenever two sets of objects are aggregated together. More...
 
- Protected Member Functions inherited from ns3::ObjectBase
void ConstructSelf (const AttributeConstructionList &attributes)
 
virtual void NotifyConstructionCompleted (void)
 This method is invoked once all member attributes have been initialized. More...
 

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

- Static Public Member Functions inherited from ns3::Synchronizer
static TypeId GetTypeId (void)
 
- Static Public Member Functions inherited from ns3::Object
static TypeId GetTypeId (void)
 Register this type. More...
 
- Static Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
static void Cleanup (void)
 Noop. More...
 
- Static Public Member Functions inherited from ns3::ObjectBase
static TypeId GetTypeId (void)
 Get the type ID. More...
 

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.

Constructor & Destructor Documentation

ns3::WallClockSynchronizer::WallClockSynchronizer ( )

Definition at line 31 of file wall-clock-synchronizer.cc.

References m_jiffy, NS_LOG_FUNCTION, NS_LOG_INFO, and NS_PER_SEC.

ns3::WallClockSynchronizer::~WallClockSynchronizer ( )
virtual

Definition at line 71 of file wall-clock-synchronizer.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

uint64_t ns3::WallClockSynchronizer::DoEventEnd ( void  )
protectedvirtual

Implements ns3::Synchronizer.

Definition at line 288 of file wall-clock-synchronizer.cc.

References GetNormalizedRealtime(), m_nsEventStart, and NS_LOG_FUNCTION.

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void ns3::WallClockSynchronizer::DoEventStart ( void  )
protectedvirtual

Implements ns3::Synchronizer.

Definition at line 281 of file wall-clock-synchronizer.cc.

References GetNormalizedRealtime(), m_nsEventStart, and NS_LOG_FUNCTION.

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uint64_t ns3::WallClockSynchronizer::DoGetCurrentRealtime ( void  )
protectedvirtual

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

Internal:

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 GetNormalizedRealtime(), and NS_LOG_FUNCTION.

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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.

Internal:
Parameters
nsSimulation 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 GetNormalizedRealtime(), and NS_LOG_FUNCTION.

Referenced by DoSynchronize(), and DriftCorrect().

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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.

Internal:

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

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

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

Internal:

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
nsThe 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 GetRealtime(), ns3::Synchronizer::m_realtimeOriginNano, NS_LOG_FUNCTION, and NS_LOG_INFO.

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

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

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

Internal:

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
nsCurrentThe current simulation time.
nsDelayThe simulation time of the next event (in nanosecond units).
See also
TimeStepPrecision::Get

Implements ns3::Synchronizer.

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

References DoGetDrift(), DriftCorrect(), m_jiffy, NS_LOG_FUNCTION, NS_LOG_INFO, SleepWait(), and SpinWait().

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uint64_t ns3::WallClockSynchronizer::DriftCorrect ( uint64_t  nsNow,
uint64_t  nsDelay 
)
protected

Definition at line 349 of file wall-clock-synchronizer.cc.

References DoGetDrift(), and NS_LOG_FUNCTION.

Referenced by DoSynchronize().

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uint64_t ns3::WallClockSynchronizer::GetNormalizedRealtime ( void  )
protected

Definition at line 389 of file wall-clock-synchronizer.cc.

References GetRealtime(), ns3::Synchronizer::m_realtimeOriginNano, and NS_LOG_FUNCTION.

Referenced by DoEventEnd(), DoEventStart(), DoGetCurrentRealtime(), DoGetDrift(), and SpinWait().

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uint64_t ns3::WallClockSynchronizer::GetRealtime ( void  )
protected

Definition at line 380 of file wall-clock-synchronizer.cc.

References NS_LOG_FUNCTION, and TimevalToNs().

Referenced by DoSetOrigin(), and GetNormalizedRealtime().

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void ns3::WallClockSynchronizer::NsToTimeval ( int64_t  ns,
struct timeval *  tv 
)
protected

Definition at line 396 of file wall-clock-synchronizer.cc.

References NS_ASSERT, NS_LOG_FUNCTION, NS_PER_SEC, and US_PER_NS.

bool ns3::WallClockSynchronizer::SleepWait ( uint64_t  ns)
protected

Definition at line 323 of file wall-clock-synchronizer.cc.

References m_condition, NS_LOG_FUNCTION, and ns3::SystemCondition::TimedWait().

Referenced by DoSynchronize().

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bool ns3::WallClockSynchronizer::SpinWait ( uint64_t  ns)
protected

Definition at line 295 of file wall-clock-synchronizer.cc.

References ns3::SystemCondition::GetCondition(), GetNormalizedRealtime(), m_condition, and NS_LOG_FUNCTION.

Referenced by DoSynchronize().

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void ns3::WallClockSynchronizer::TimevalAdd ( struct timeval *  tv1,
struct timeval *  tv2,
struct timeval *  result 
)
protected

Definition at line 414 of file wall-clock-synchronizer.cc.

References NS_LOG_FUNCTION, and US_PER_SEC.

uint64_t ns3::WallClockSynchronizer::TimevalToNs ( struct timeval *  tv)
protected

Definition at line 405 of file wall-clock-synchronizer.cc.

References NS_ASSERT, NS_LOG_FUNCTION, NS_PER_SEC, and US_PER_NS.

Referenced by GetRealtime().

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Member Data Documentation

SystemCondition ns3::WallClockSynchronizer::m_condition
protected

Definition at line 193 of file wall-clock-synchronizer.h.

Referenced by DoSetCondition(), DoSignal(), SleepWait(), and SpinWait().

uint64_t ns3::WallClockSynchronizer::m_cpuTick
protected

Definition at line 188 of file wall-clock-synchronizer.h.

uint64_t ns3::WallClockSynchronizer::m_jiffy
protected

Definition at line 190 of file wall-clock-synchronizer.h.

Referenced by DoSynchronize(), and WallClockSynchronizer().

uint64_t ns3::WallClockSynchronizer::m_nsEventStart
protected

Definition at line 191 of file wall-clock-synchronizer.h.

Referenced by DoEventEnd(), and DoEventStart().

uint64_t ns3::WallClockSynchronizer::m_realtimeTick
protected

Definition at line 189 of file wall-clock-synchronizer.h.

const uint64_t ns3::WallClockSynchronizer::NS_PER_SEC = (uint64_t)1000000000
static

Conversion from ns to s.

Definition at line 71 of file wall-clock-synchronizer.h.

Referenced by NsToTimeval(), TimevalToNs(), and WallClockSynchronizer().

const uint64_t ns3::WallClockSynchronizer::US_PER_NS = (uint64_t)1000
static

Definition at line 68 of file wall-clock-synchronizer.h.

Referenced by NsToTimeval(), and TimevalToNs().

const uint64_t ns3::WallClockSynchronizer::US_PER_SEC = (uint64_t)1000000
static

Definition at line 69 of file wall-clock-synchronizer.h.

Referenced by TimevalAdd().


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