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gh-63207: Use GetSystemTimePreciseAsFileTime() in time.time() #116822

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merged 1 commit into from
Mar 18, 2024
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gh-63207: Use GetSystemTimePreciseAsFileTime() in time.time() #116822

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6 changes: 6 additions & 0 deletions Doc/whatsnew/3.13.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -560,6 +560,12 @@ time
instead of the ``GetTickCount64()`` clock which has a resolution of 15.6 ms.
(Contributed by Victor Stinner in :gh:`88494`.)

* On Windows, :func:`time.time()` now uses the
``GetSystemTimePreciseAsFileTime()`` clock to have a resolution better
than 1 us, instead of the ``GetSystemTimeAsFileTime()`` clock which has a
resolution of 15.6 ms.
(Contributed by Victor Stinner in :gh:`63207`.)


tkinter
-------
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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2024-03-14-17-21-25.gh-issue-63207.LV16SL.rst
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@@ -0,0 +1,4 @@
On Windows, :func:`time.time()` now uses the
``GetSystemTimePreciseAsFileTime()`` clock to have a resolution better than 1
us, instead of the ``GetSystemTimeAsFileTime()`` clock which has a resolution
of 15.6 ms. Patch by Victor Stinner.
38 changes: 22 additions & 16 deletions Python/pytime.c
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Expand Up @@ -55,6 +55,14 @@
#endif


#ifdef MS_WINDOWS
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Yes, I think checking for MS_WINDOWS here is sufficient. GetSystemTimePreciseAsFileTime(), QueryPerformanceCounter(), and QueryPerformanceFrequency() are available in the system, app, and game partitions. The old use of GetSystemTimeAdjustment() actually wasn't supported for app builds. However, that function was used improperly anyway.

static _PyTimeFraction py_qpc_base = {0, 0};

// Forward declaration
static int py_win_perf_counter_frequency(_PyTimeFraction *base, int raise_exc);
#endif


static PyTime_t
_PyTime_GCD(PyTime_t x, PyTime_t y)
{
Expand Down Expand Up @@ -895,7 +903,7 @@ py_get_system_clock(PyTime_t *tp, _Py_clock_info_t *info, int raise_exc)
FILETIME system_time;
ULARGE_INTEGER large;

GetSystemTimeAsFileTime(&system_time);
GetSystemTimePreciseAsFileTime(&system_time);
large.u.LowPart = system_time.dwLowDateTime;
large.u.HighPart = system_time.dwHighDateTime;
/* 11,644,473,600,000,000,000: number of nanoseconds between
Expand All @@ -904,18 +912,17 @@ py_get_system_clock(PyTime_t *tp, _Py_clock_info_t *info, int raise_exc)
PyTime_t ns = large.QuadPart * 100 - 11644473600000000000;
*tp = ns;
if (info) {
DWORD timeAdjustment, timeIncrement;
BOOL isTimeAdjustmentDisabled, ok;
// GetSystemTimePreciseAsFileTime() is implemented using
// QueryPerformanceCounter() internally.
if (py_qpc_base.denom == 0) {
if (py_win_perf_counter_frequency(&py_qpc_base, raise_exc) < 0) {
return -1;
}
}

info->implementation = "GetSystemTimeAsFileTime()";
info->implementation = "GetSystemTimePreciseAsFileTime()";
info->monotonic = 0;
ok = GetSystemTimeAdjustment(&timeAdjustment, &timeIncrement,
&isTimeAdjustmentDisabled);
if (!ok) {
PyErr_SetFromWindowsErr(0);
return -1;
}
info->resolution = timeIncrement * 1e-7;
info->resolution = _PyTimeFraction_Resolution(&py_qpc_base);
info->adjustable = 1;
}

Expand Down Expand Up @@ -1063,16 +1070,15 @@ py_get_win_perf_counter(PyTime_t *tp, _Py_clock_info_t *info, int raise_exc)
{
assert(info == NULL || raise_exc);

static _PyTimeFraction base = {0, 0};
if (base.denom == 0) {
if (py_win_perf_counter_frequency(&base, raise_exc) < 0) {
if (py_qpc_base.denom == 0) {
if (py_win_perf_counter_frequency(&py_qpc_base, raise_exc) < 0) {
return -1;
}
}

if (info) {
info->implementation = "QueryPerformanceCounter()";
info->resolution = _PyTimeFraction_Resolution(&base);
info->resolution = _PyTimeFraction_Resolution(&py_qpc_base);
info->monotonic = 1;
info->adjustable = 0;
}
Expand All @@ -1088,7 +1094,7 @@ py_get_win_perf_counter(PyTime_t *tp, _Py_clock_info_t *info, int raise_exc)
"LONGLONG is larger than PyTime_t");
ticks = (PyTime_t)ticksll;

*tp = _PyTimeFraction_Mul(ticks, &base);
*tp = _PyTimeFraction_Mul(ticks, &py_qpc_base);
return 0;
}
#endif // MS_WINDOWS
Expand Down