src/third_party/skia/tools/timer/SysTimer_windows.cpp

   1 /*
   2  * Copyright 2011 Google Inc.
   3  *
   4  * Use of this source code is governed by a BSD-style license that can be
   5  * found in the LICENSE file.
   6  */
   7 #include "SysTimer_windows.h"
   8
   9 #include <intrin.h>
  10
  11 static ULONGLONG win_cpu_time() {
  12     FILETIME createTime;
  13     FILETIME exitTime;
  14     FILETIME usrTime;
  15     FILETIME sysTime;
  16     if (0 == GetProcessTimes(GetCurrentProcess(), &createTime, &exitTime, &sysTime, &usrTime)) {
  17         return 0;
  18     }
  19     ULARGE_INTEGER start_cpu_sys;
  20     ULARGE_INTEGER start_cpu_usr;
  21     start_cpu_sys.LowPart  = sysTime.dwLowDateTime;
  22     start_cpu_sys.HighPart = sysTime.dwHighDateTime;
  23     start_cpu_usr.LowPart  = usrTime.dwLowDateTime;
  24     start_cpu_usr.HighPart = usrTime.dwHighDateTime;
  25     return start_cpu_sys.QuadPart + start_cpu_usr.QuadPart;
  26 }
  27
  28 void SysTimer::startCpu() {
  29     fStartCpu = win_cpu_time();
  30 }
  31
  32 double SysTimer::endCpu() {
  33     ULONGLONG end_cpu = win_cpu_time();
  34     return static_cast<double>(end_cpu - fStartCpu) / 10000.0L;
  35 }
  36
  37 // On recent Intel chips (roughly, "has Core or Atom in its name") __rdtsc will always tick
  38 // at the CPU's maximum rate, even while power management clocks the CPU up and down.
  39 // That's great, because it makes measuring wall time super simple.
  40
  41 void SysTimer::startWall() {
  42     fStartWall = __rdtsc();
  43 }
  44
  45 double SysTimer::endWall() {
  46     unsigned __int64 end = __rdtsc();
  47
  48     // This seems to, weirdly, give the CPU frequency in kHz.  That's exactly what we want!
  49     LARGE_INTEGER freq_khz;
  50     QueryPerformanceFrequency(&freq_khz);
  51
  52     return static_cast<double>(end - fStartWall) / static_cast<double>(freq_khz.QuadPart);
  53 }