mirror of
https://github.com/reactos/reactos.git
synced 2024-09-06 10:52:52 +00:00
[NTVDM]
Improve performance by computing the resolution required by the PIT, and then using the standard tick count instead of performance counters when that resolution is low. svn path=/branches/ntvdm/; revision=60783
This commit is contained in:
parent
b8d8b21ebd
commit
97acc35c7c
|
@ -151,19 +151,37 @@ INT wmain(INT argc, WCHAR *argv[])
|
|||
/* Main loop */
|
||||
while (VdmRunning)
|
||||
{
|
||||
/* Get the resolution of the system timer */
|
||||
DWORD TimerResolution = PitGetResolution();
|
||||
|
||||
/* Get the current number of ticks */
|
||||
CurrentTickCount = GetTickCount();
|
||||
|
||||
if (TimerResolution > 1000)
|
||||
{
|
||||
/* Get the current performance counter value */
|
||||
QueryPerformanceCounter(&Counter);
|
||||
|
||||
/* Get the number of PIT ticks that have passed */
|
||||
TimerTicks = ((Counter.QuadPart - LastTimerTick.QuadPart)
|
||||
* PIT_BASE_FREQUENCY) / Frequency.QuadPart;
|
||||
}
|
||||
else
|
||||
{
|
||||
/* Use the standard tick count */
|
||||
Counter.QuadPart = CurrentTickCount;
|
||||
|
||||
/* Get the number of PIT ticks that have passed */
|
||||
TimerTicks = ((Counter.QuadPart - LastTimerTick.QuadPart)
|
||||
* PIT_BASE_FREQUENCY) / 1000;
|
||||
}
|
||||
|
||||
/* Update the PIT */
|
||||
if (TimerTicks > 0)
|
||||
{
|
||||
for (i = 0; i < TimerTicks; i++) PitDecrementCount();
|
||||
LastTimerTick = Counter;
|
||||
}
|
||||
|
||||
/* Check for vertical retrace */
|
||||
if ((CurrentTickCount - LastVerticalRefresh) >= 16)
|
||||
|
|
|
@ -233,4 +233,23 @@ VOID PitDecrementCount()
|
|||
}
|
||||
}
|
||||
|
||||
DWORD PitGetResolution(VOID)
|
||||
{
|
||||
INT i;
|
||||
DWORD MinReloadValue = 65536;
|
||||
|
||||
for (i = 0; i < PIT_CHANNELS; i++)
|
||||
{
|
||||
DWORD ReloadValue = PitChannels[i].ReloadValue;
|
||||
|
||||
/* 0 means 65536 */
|
||||
if (ReloadValue == 0) ReloadValue = 65536;
|
||||
|
||||
if (ReloadValue < MinReloadValue) MinReloadValue = ReloadValue;
|
||||
}
|
||||
|
||||
/* Return the frequency resolution */
|
||||
return PIT_BASE_FREQUENCY / MinReloadValue;
|
||||
}
|
||||
|
||||
/* EOF */
|
||||
|
|
|
@ -49,6 +49,7 @@ VOID PitWriteCommand(BYTE Value);
|
|||
BYTE PitReadData(BYTE Channel);
|
||||
VOID PitWriteData(BYTE Channel, BYTE Value);
|
||||
VOID PitDecrementCount();
|
||||
DWORD PitGetResolution(VOID);
|
||||
|
||||
#endif // _TIMER_H_
|
||||
|
||||
|
|
Loading…
Reference in a new issue