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Side by Side Diff: tools/timer/SysTimer_windows.cpp

Issue 1420923003: Revert of SkTime::GetNSecs() (Closed) Base URL: https://skia.googlesource.com/skia.git@master
Patch Set: Created 5 years, 2 months ago
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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, &sysTi me, &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 wh at 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 }
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