bpo-37205: time.perf_counter() and time.monotonic() are system-wide (GH-23284)
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.
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@ -166,6 +166,9 @@ Functions
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Return the time of the specified clock *clk_id*. Refer to
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:ref:`time-clock-id-constants` for a list of accepted values for *clk_id*.
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Use :func:`clock_gettime_ns` to avoid the precision loss caused by the
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:class:`float` type.
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.. availability:: Unix.
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.. versionadded:: 3.3
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@ -185,6 +188,9 @@ Functions
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Set the time of the specified clock *clk_id*. Currently,
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:data:`CLOCK_REALTIME` is the only accepted value for *clk_id*.
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Use :func:`clock_settime_ns` to avoid the precision loss caused by the
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:class:`float` type.
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.. availability:: Unix.
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.. versionadded:: 3.3
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@ -273,10 +279,17 @@ Functions
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The reference point of the returned value is undefined, so that only the
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difference between the results of consecutive calls is valid.
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Use :func:`monotonic_ns` to avoid the precision loss caused by the
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:class:`float` type.
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.. versionadded:: 3.3
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.. versionchanged:: 3.5
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The function is now always available and always system-wide.
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.. versionchanged:: 3.10
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On macOS, the function is now system-wide.
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.. function:: monotonic_ns() -> int
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@ -295,8 +308,14 @@ Functions
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point of the returned value is undefined, so that only the difference between
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the results of consecutive calls is valid.
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Use :func:`perf_counter_ns` to avoid the precision loss caused by the
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:class:`float` type.
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.. versionadded:: 3.3
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.. versionchanged:: 3.10
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On Windows, the function is now system-wide.
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.. function:: perf_counter_ns() -> int
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Similar to :func:`perf_counter`, but return time as nanoseconds.
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@ -317,6 +336,9 @@ Functions
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returned value is undefined, so that only the difference between the results
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of consecutive calls is valid.
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Use :func:`process_time_ns` to avoid the precision loss caused by the
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:class:`float` type.
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.. versionadded:: 3.3
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.. function:: process_time_ns() -> int
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@ -581,6 +603,17 @@ Functions
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:class:`struct_time` object is returned, from which the components
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of the calendar date may be accessed as attributes.
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Use :func:`time_ns` to avoid the precision loss caused by the :class:`float`
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type.
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.. function:: time_ns() -> int
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Similar to :func:`~time.time` but returns time as an integer number of nanoseconds
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since the epoch_.
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.. versionadded:: 3.7
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.. function:: thread_time() -> float
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@ -595,6 +628,9 @@ Functions
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returned value is undefined, so that only the difference between the results
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of consecutive calls in the same thread is valid.
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Use :func:`thread_time_ns` to avoid the precision loss caused by the
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:class:`float` type.
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.. availability:: Windows, Linux, Unix systems supporting
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``CLOCK_THREAD_CPUTIME_ID``.
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@ -608,13 +644,6 @@ Functions
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.. versionadded:: 3.7
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.. function:: time_ns() -> int
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Similar to :func:`~time.time` but returns time as an integer number of nanoseconds
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since the epoch_.
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.. versionadded:: 3.7
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.. function:: tzset()
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Reset the time conversion rules used by the library routines. The environment
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@ -0,0 +1,5 @@
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:func:`time.perf_counter()` on Windows and :func:`time.monotonic()` on macOS
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are now system-wide. Previously, they used an offset computed at startup to
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reduce the precision loss caused by the float type. Use
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:func:`time.perf_counter_ns()` and :func:`time.monotonic_ns()` added in Python
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3.7 to avoid this precision loss.
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@ -6,7 +6,7 @@
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#if defined(__APPLE__)
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#include <mach/mach_time.h> /* mach_absolute_time(), mach_timebase_info() */
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#if defined(__APPLE__) && defined(__has_builtin)
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#if defined(__APPLE__) && defined(__has_builtin)
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# if __has_builtin(__builtin_available)
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# define HAVE_CLOCK_GETTIME_RUNTIME __builtin_available(macOS 10.12, iOS 10.0, tvOS 10.0, watchOS 3.0, *)
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# endif
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@ -730,7 +730,7 @@ pygettimeofday(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
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}
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#ifdef HAVE_CLOCK_GETTIME_RUNTIME
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} else {
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} else {
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#endif
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#endif
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@ -822,7 +822,6 @@ pymonotonic(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
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#elif defined(__APPLE__)
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static mach_timebase_info_data_t timebase;
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static uint64_t t0 = 0;
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uint64_t ticks;
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if (timebase.denom == 0) {
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@ -859,8 +858,6 @@ pymonotonic(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
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"mach_timebase_info is too large");
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return -1;
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}
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t0 = mach_absolute_time();
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}
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if (info) {
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@ -871,9 +868,6 @@ pymonotonic(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
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}
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ticks = mach_absolute_time();
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/* Use a "time zero" to reduce precision loss when converting time
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to floatting point number, as in time.monotonic(). */
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ticks -= t0;
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*tp = _PyTime_MulDiv(ticks,
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(_PyTime_t)timebase.numer,
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(_PyTime_t)timebase.denom);
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@ -960,7 +954,6 @@ static int
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win_perf_counter(_PyTime_t *tp, _Py_clock_info_t *info)
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{
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static LONGLONG frequency = 0;
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static LONGLONG t0 = 0;
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LARGE_INTEGER now;
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LONGLONG ticksll;
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_PyTime_t ticks;
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@ -1000,7 +993,6 @@ win_perf_counter(_PyTime_t *tp, _Py_clock_info_t *info)
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}
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QueryPerformanceCounter(&now);
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t0 = now.QuadPart;
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}
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if (info) {
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@ -1013,10 +1005,6 @@ win_perf_counter(_PyTime_t *tp, _Py_clock_info_t *info)
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QueryPerformanceCounter(&now);
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ticksll = now.QuadPart;
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/* Use a "time zero" to reduce precision loss when converting time
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to floatting point number, as in time.perf_counter(). */
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ticksll -= t0;
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/* Make sure that casting LONGLONG to _PyTime_t cannot overflow,
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both types are signed */
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Py_BUILD_ASSERT(sizeof(ticksll) <= sizeof(ticks));
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