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bpo-41303: Use mac_continuous_time for perf_counter on macOS 10.12+ #21719

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bpo-41303: Use mac_continuous_time for perf_counter on macOS 10.12+ #21719

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4d365d6
bpo-41303:[macOS] Use better clock in perf_counter
xrisk Aug 3, 2020
cc6bbae
Merge github.com:python/cpython into perf_counter
xrisk Aug 3, 2020
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1 change: 1 addition & 0 deletions Doc/library/time.rst
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Expand Up @@ -295,6 +295,7 @@ Functions
point of the returned value is undefined, so that only the difference between
the results of consecutive calls is valid.

.. note:: On macOS versions prior to 10.12, perf_counter does not track time elapsed during sleep.
.. versionadded:: 3.3

.. function:: perf_counter_ns() -> int
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1 change: 1 addition & 0 deletions Misc/ACKS
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Expand Up @@ -940,6 +940,7 @@ Dave Kuhlman
Jon Kuhn
Ilya Kulakov
Upendra Kumar
Rishav Kundu
Toshio Kuratomi
Ilia Kurenkov
Vladimir Kushnir
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2020-08-04-03-20-08.bpo-41303.yA0SYM.rst
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@@ -0,0 +1 @@
time.perf_counter now tracks time elapsed during sleep on macOS 10.12+.
13 changes: 13 additions & 0 deletions Python/pytime.c
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Expand Up @@ -835,17 +835,30 @@ pymonotonic(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
return -1;
}

#ifdef __MAC_10_12
t0 = mach_continuous_time();
#else
t0 = mach_absolute_time();
#endif
}

if (info) {
#ifdef __MAC_10_12
info->implementation = "mach_continuous_time()";
#else
info->implementation = "mach_absolute_time()";
#endif
info->resolution = (double)timebase.numer / (double)timebase.denom * 1e-9;
info->monotonic = 1;
info->adjustable = 0;
}

#ifdef __MAC_10_12
ticks = mach_continuous_time();
#else
ticks = mach_absolute_time();
#endif

/* Use a "time zero" to reduce precision loss when converting time
to floatting point number, as in time.monotonic(). */
ticks -= t0;
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