Merge branch 'arm-detect-pmull' of https://github.com/sitsofe/fio
[fio.git] / os / windows / dlls.c
1 #include "os/os.h"
2
3 #include <windows.h>
4
5 void os_clk_tck(long *clk_tck)
6 {
7         /*
8          * The timer resolution is variable on Windows. Try to query it 
9          * or use 64 Hz, the clock frequency lower bound. See also
10          * https://carpediemsystems.co.uk/2019/07/18/windows-system-timer-granularity/.
11          */
12         unsigned long minRes, maxRes, curRes;
13         HMODULE lib;
14         FARPROC queryTimer;
15         FARPROC setTimer;
16
17         if (!(lib = LoadLibrary(TEXT("ntdll.dll"))) ||
18                 !(queryTimer = GetProcAddress(lib, "NtQueryTimerResolution")) ||
19                 !(setTimer = GetProcAddress(lib, "NtSetTimerResolution"))) {
20                 dprint(FD_HELPERTHREAD, 
21                         "Failed to load ntdll library, set to lower bound 64 Hz\n");
22                 *clk_tck = 64;
23         } else {
24                 queryTimer(&minRes, &maxRes, &curRes);
25                 dprint(FD_HELPERTHREAD, 
26                         "minRes = %lu, maxRes = %lu, curRes = %lu\n",
27                         minRes, maxRes, curRes);
28
29                 /* Use maximum resolution for most accurate timestamps */
30                 setTimer(maxRes, 1, &curRes);
31                 *clk_tck = (long) (10000000L / maxRes);
32         }
33 }