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- Went back to using RDTSC for timing on Win32. Ironically,

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QueryPerformanceCounter() is obviously using the TSC for its timing on my
  machine, yet the overhead it has to do to keep the timer sane is apparently
  noticeable on a few maps. I suppose I should at some time check
  clock_gettime() and see if it has similar issues on Linux.


SVN r1460 (trunk)
This commit is contained in:
Randy Heit 2009-03-04 06:06:31 +00:00
commit 5eeaa130fd
4 changed files with 109 additions and 27 deletions
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53
src/win32/i_system.cpp
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@ -372,21 +372,62 @@ void SetLanguageIDs ()
}
}
void CalculateCPUSpeed()
{
LARGE_INTEGER freq;
QueryPerformanceFrequency (&freq);
if (freq.QuadPart != 0 && CPU.bRDTSC)
{
LARGE_INTEGER count1, count2;
cycle_t ClockCalibration;
DWORD min_diff;
ClockCalibration.Reset();
// Count cycles for at least 55 milliseconds.
// The performance counter may be very low resolution compared to CPU
// speeds today, so the longer we count, the more accurate our estimate.
// On the other hand, we don't want to count too long, because we don't
// want the user to notice us spend time here, since most users will
// probably never use the performance statistics.
min_diff = freq.LowPart * 11 / 200;
// Minimize the chance of task switching during the testing by going very
// high priority. This is another reason to avoid timing for too long.
SetPriorityClass(GetCurrentProcess(), REALTIME_PRIORITY_CLASS);
SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_TIME_CRITICAL);
// Make sure we start timing on a counter boundary.
QueryPerformanceCounter(&count1);
do { QueryPerformanceCounter(&count2); } while (count1.QuadPart == count2.QuadPart);
// Do the timing loop.
ClockCalibration.Clock();
do { QueryPerformanceCounter(&count1); } while ((count1.QuadPart - count2.QuadPart) < min_diff);
ClockCalibration.Unclock();
SetPriorityClass(GetCurrentProcess(), NORMAL_PRIORITY_CLASS);
SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_NORMAL);
PerfToSec = double(count1.QuadPart - count2.QuadPart) / (double(ClockCalibration.GetRawCounter()) * freq.QuadPart);
PerfToMillisec = PerfToSec * 1000.0;
}
Printf ("CPU Speed: %.0f MHz\n", 0.001 / PerfToMillisec);
}
//
// I_Init
//
void I_Init (void)
{
LARGE_INTEGER perf_freq;
CheckCPUID(&CPU);
CalculateCPUSpeed();
DumpCPUInfo(&CPU);
QueryPerformanceFrequency(&perf_freq);
PerfToSec = 1 / double(perf_freq.QuadPart);
PerfToMillisec = 1000 / double(perf_freq.QuadPart);
// Use a timer event if possible
NewTicArrived = CreateEvent (NULL, FALSE, FALSE, NULL);
if (NewTicArrived)