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/*
* Copyright 2011 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SysTimer_windows.h"
#include <intrin.h>
static ULONGLONG win_cpu_time() {
FILETIME createTime;
FILETIME exitTime;
FILETIME usrTime;
FILETIME sysTime;
if (0 == GetProcessTimes(GetCurrentProcess(), &createTime, &exitTime, &sysTime, &usrTime)) {
return 0;
}
ULARGE_INTEGER start_cpu_sys;
ULARGE_INTEGER start_cpu_usr;
start_cpu_sys.LowPart = sysTime.dwLowDateTime;
start_cpu_sys.HighPart = sysTime.dwHighDateTime;
start_cpu_usr.LowPart = usrTime.dwLowDateTime;
start_cpu_usr.HighPart = usrTime.dwHighDateTime;
return start_cpu_sys.QuadPart + start_cpu_usr.QuadPart;
}
void SysTimer::startCpu() {
fStartCpu = win_cpu_time();
}
double SysTimer::endCpu() {
ULONGLONG end_cpu = win_cpu_time();
return static_cast<double>(end_cpu - fStartCpu) / 10000.0L;
}
// On recent Intel chips (roughly, "has Core or Atom in its name") __rdtsc will always tick
// at the CPU's maximum rate, even while power management clocks the CPU up and down.
// That's great, because it makes measuring wall time super simple.
void SysTimer::startWall() {
fStartWall = __rdtsc();
}
double SysTimer::endWall() {
unsigned __int64 end = __rdtsc();
// This seems to, weirdly, give the CPU frequency in kHz. That's exactly what we want!
LARGE_INTEGER freq_khz;
QueryPerformanceFrequency(&freq_khz);
return static_cast<double>(end - fStartWall) / static_cast<double>(freq_khz.QuadPart);
}
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