Timer functions to interrupt VM execution after a number of simulation ticks. More...

#include <timer.hh>

Inheritance diagram for BaseKvmTimer:

Public Member Functions
	BaseKvmTimer (int signo, float hostFactor, Tick hostFreq)
	Setup basic timer functionality shared by all timer implementations. More...

virtual	~BaseKvmTimer ()

virtual void	arm (Tick ticks)=0
	Arm the timer so that it fires after a certain number of ticks. More...

virtual void	disarm ()=0
	Disarm the timer. More...

Tick	resolution ()
	Determine the resolution of the timer in ticks. More...

Tick	ticksFromHostCycles (uint64_t cycles)
	Convert cycles executed on the host into Ticks executed in the simulator. More...

Tick	ticksFromHostNs (uint64_t ns)
	Convert nanoseconds executed on the host into Ticks executed in the simulator. More...

Protected Member Functions
virtual Tick	calcResolution ()=0
	Calculate the timer resolution, used by resolution() which caches the result. More...

uint64_t	hostNs (Tick ticks)
	Convert a time in simulator ticks to host nanoseconds. More...

uint64_t	hostCycles (Tick ticks)
	Convert a time in simulator ticks to host cycles. More...

Protected Attributes
int	signo
	Signal to deliver when the timer times out. More...

Private Attributes
Tick	_resolution
	Cached resolution. More...

float	hostFactor
	Performance scaling factor. More...

Tick	hostFreq
	Host frequency. More...

Detailed Description

Timer functions to interrupt VM execution after a number of simulation ticks.

The timer allows scaling of the host time to take performance differences between the simulated and real CPU into account.

The performance scaling factor is ratio between the target's CPI and the host's CPI. It is larger than 1 if the host is faster than the target and lower than 1 if it is slower.

When the timer times out, it sends a signal to the thread that started the timer. The signal forces KVM to drop out of the system call that started the guest and hands control to gem5.

Definition at line 62 of file timer.hh.

Constructor & Destructor Documentation

BaseKvmTimer::BaseKvmTimer	(	int	signo,
		float	hostFactor,
		Tick	hostFreq
	)

inline

Setup basic timer functionality shared by all timer implementations.

Parameters

signo	Signal to deliver
hostFactor	Performance scaling factor
hostFreq	Clock frequency of the host

Definition at line 73 of file timer.hh.

virtual BaseKvmTimer::~BaseKvmTimer ( )

inlinevirtual

Definition at line 76 of file timer.hh.

Member Function Documentation

virtual void BaseKvmTimer::arm ( Tick ticks )

pure virtual

Arm the timer so that it fires after a certain number of ticks.

Note: A timer implementation is free to convert between simulation ticks and virtualized time using any method it chooses. The accuracy of the timer therefore depends on what it measures, an accurate timer implementation should measure the number of cycles or instructions executed in the guest. If such counters are unavailable, it may fallback to wall clock time.

Parameters

ticks Number of ticks until the timer fires

Implemented in PerfKvmTimer, and PosixKvmTimer.

virtual Tick BaseKvmTimer::calcResolution ( )

protectedpure virtual

Calculate the timer resolution, used by resolution() which caches the result.