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bpo-37205: time.perf_counter() and time.monotonic() are system-wide (GH-23284)

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time.perf_counter() on Windows and time.monotonic() on macOS are now
system-wide. Previously, they used an offset computed at startup to
reduce the precision loss caused by the float type. Use
time.perf_counter_ns() and time.monotonic_ns() added in Python 3.7 to
avoid this precision loss.
This commit is contained in:
Victor Stinner 2020-11-16 13:21:45 +01:00 • committed by GitHub
parent aa01011003
commit 3df5c68487
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 43 additions and 21 deletions
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16
Python/pytime.c
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@ -6,7 +6,7 @@
#if defined(__APPLE__)
#include <mach/mach_time.h> /* mach_absolute_time(), mach_timebase_info() */
#if defined(__APPLE__) && defined(__has_builtin)
#if defined(__APPLE__) && defined(__has_builtin)
# if __has_builtin(__builtin_available)
# define HAVE_CLOCK_GETTIME_RUNTIME __builtin_available(macOS 10.12, iOS 10.0, tvOS 10.0, watchOS 3.0, *)
# endif
@ -730,7 +730,7 @@ pygettimeofday(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
}
#ifdef HAVE_CLOCK_GETTIME_RUNTIME
} else {
} else {
#endif
#endif
@ -822,7 +822,6 @@ pymonotonic(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
#elif defined(__APPLE__)
static mach_timebase_info_data_t timebase;
static uint64_t t0 = 0;
uint64_t ticks;
if (timebase.denom == 0) {
@ -859,8 +858,6 @@ pymonotonic(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
"mach_timebase_info is too large");
return -1;
}
t0 = mach_absolute_time();
}
if (info) {
@ -871,9 +868,6 @@ pymonotonic(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
}
ticks = mach_absolute_time();
/* Use a "time zero" to reduce precision loss when converting time
to floatting point number, as in time.monotonic(). */
ticks -= t0;
*tp = _PyTime_MulDiv(ticks,
(_PyTime_t)timebase.numer,
(_PyTime_t)timebase.denom);
@ -960,7 +954,6 @@ static int
win_perf_counter(_PyTime_t *tp, _Py_clock_info_t *info)
{
static LONGLONG frequency = 0;
static LONGLONG t0 = 0;
LARGE_INTEGER now;
LONGLONG ticksll;
_PyTime_t ticks;
@ -1000,7 +993,6 @@ win_perf_counter(_PyTime_t *tp, _Py_clock_info_t *info)
}
QueryPerformanceCounter(&now);
t0 = now.QuadPart;
}
if (info) {
@ -1013,10 +1005,6 @@ win_perf_counter(_PyTime_t *tp, _Py_clock_info_t *info)
QueryPerformanceCounter(&now);
ticksll = now.QuadPart;
/* Use a "time zero" to reduce precision loss when converting time
to floatting point number, as in time.perf_counter(). */
ticksll -= t0;
/* Make sure that casting LONGLONG to _PyTime_t cannot overflow,
both types are signed */
Py_BUILD_ASSERT(sizeof(ticksll) <= sizeof(ticks));