bpo-41710: gc_collect_main() uses _PyTime_GetPerfCounter()#28676

vstinner · 2021-10-01T10:59:30Z

If the DEBUG_STATS debug flag is set, gc_collect_main() now uses
_PyTime_GetPerfCounter() instead of _PyTime_GetMonotonicClock() to
measure the elapsed time.

On Windows, _PyTime_GetMonotonicClock() only has a resolution of 15.6
ms, whereas _PyTime_GetPerfCounter() is closer to a resolution of 100
ns.

https://bugs.python.org/issue41710

If the DEBUG_STATS debug flag is set, gc_collect_main() now uses _PyTime_GetPerfCounter() instead of _PyTime_GetMonotonicClock() to measure the elapsed time. On Windows, _PyTime_GetMonotonicClock() only has a resolution of 15.6 ms, whereas _PyTime_GetPerfCounter() is closer to a resolution of 100 ns.

vstinner · 2021-10-01T11:05:45Z

Code history:

First, it called time.time() and converted the result as C double
Then, it called _PyTime_gettimeofday() which uses _PyTime_timeval type
Then, it called _PyTime_monotonic() which uses _PyTime_timeval type
Then, ti called _PyTime_GetMonotonicClock() which uses _PyTime_t type

vstinner requested a review from pablogsal as a code owner October 1, 2021 10:59

bedevere-bot added the awaiting core review label Oct 1, 2021

the-knights-who-say-ni added the CLA signed label Oct 1, 2021

vstinner added the skip news label Oct 1, 2021

vstinner merged commit 54957f1 into python:main Oct 1, 2021

bedevere-bot removed the awaiting core review label Oct 1, 2021

vstinner deleted the gc_collect_perf_counter branch October 1, 2021 11:29

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bpo-41710: gc_collect_main() uses _PyTime_GetPerfCounter()#28676