public void Start()
{
// Calling start on a running Stopwatch is a no-op.
if (!isRunning)
{
startTimeStamp = GetTimestamp();
if (CPUTimeIsAvailable)
{
//Remember the Thread ID, processor number & CurrentMHz
timerStartThreadHandle = Win32.GetCurrentThread();
timerStartCPUID = Win32.GetCurrentProcessorNumber();
PROCESSOR_POWER_INFORMATION thisppi;
thisppi = CPUPowerWrapper.GetCurrentPowerInfoforProcessor();
timerStartCurrentMHz = thisppi.CurrentMhz;
timerEndCurrentMHz = thisppi.CurrentMhz;
startCPUcycles = GetCPUCycles(); //CPU Cycles consumed by the thread up to this point
elapsedCPUThisPeriod = 0;
}
isRunning = true;
}
}
public void Stop()
{
// Calling stop on a stopped Stopwatch is a no-op.
if (isRunning)
{
long endTimeStamp = 0;
endTimeStamp = GetTimestamp();
if (CPUTimeIsAvailable)
{
timerEndThreadHandle = Win32.GetCurrentThread();
long endCPUcycles = GetCPUCycles(); //Get CPU Cycles first
if (timerEndThreadHandle != timerStartThreadHandle)
{
threadSwitchOccurred = true; //A thread switch is a problem, since CPU Cycles are accumulated
endCPUcycles = 0; // at the thread level
startCPUcycles = 0;
}
else
{
if (endCPUcycles > startCPUcycles)
{
elapsedCPUThisPeriod = endCPUcycles - startCPUcycles;
elapsedCPU += elapsedCPUThisPeriod;
}
//How likely is it for the CPU time accumulator to wrap???
else
{
elapsedCPU = 0;
endCPUcycles = 0;
startCPUcycles = 0;
}
}
}
long elapsedThisPeriod = endTimeStamp - startTimeStamp;
elapsed += elapsedThisPeriod;
isRunning = false;
if (elapsed < 0)
{
// When measuring small time periods the StopWatch.Elapsed*
// properties can return negative values. This is due to
// bugs in the basic input/output system (BIOS) or the hardware
// abstraction layer (HAL) on machines with variable-speed CPUs
// (e.g. Intel SpeedStep).
elapsed = 0;
}
if (CPUTimeIsAvailable && elapsedCPU > 0)
{
timerEndCPUID = Win32.GetCurrentProcessorNumber();
if (timerEndCPUID != timerStartCPUID)
{
// Exposed as the FinishedOnDifferentProcessor property
// Stopwatch cannot detect context switches in general,
// but we do know at least one context switch occurred in this case
//
cpuSwitchOccurred = true;
}
PROCESSOR_POWER_INFORMATION thisppi = CPUPowerWrapper.GetCurrentPowerInfoforProcessor();
timerEndCurrentMHz = thisppi.CurrentMhz;
timerEndMaxMHz = thisppi.MaxMhz;
if (timerStartCurrentMHz != timerEndCurrentMHz) // CPU speed change detected
{
// Exposed as the PowerManagementChangeOccurred property
// so long as the rdtsc is constant across power management events,
// this is no cause for concern
cpuspeedChangeOccurred = true;
}
}
}
}
