[New-bugs-announce] [issue14397] Use GetTickCount/GetTickCount64 instead of QueryPerformanceCounter for monotonic clock

STINNER Victor report at bugs.python.org
Sat Mar 24 11:44:41 CET 2012


New submission from STINNER Victor <victor.stinner at gmail.com>:

QueryPerformanceCounter() is not monotonic on a multiprocessor computer on Windows XP. Extract of its documentation:

"Remarks

On a multiprocessor computer, it should not matter which processor is called. However, you can get different results on different processors due to bugs in the basic input/output system (BIOS) or the hardware abstraction layer (HAL). To specify processor affinity for a thread, use the SetThreadAffinityMask function." 

See also:
http://bytes.com/topic/python/answers/527849-time-clock-going-backwards

time.steady(strict-True) (or "time.monotonic()"? the function name is not decided yet :§)) should use GetTickCounter64(), or GetTickCounter().

GetTickCount64() was added to Windows Seven / Server 2008. GetTickCount() overflows after 49 days.

QueryPerformanceCounter() has a better resolution than
GetTickCount[64]() and so it's maybe better to keep it for time.steady(strict-False)?

----------
components: Library (Lib), Windows
messages: 156690
nosy: haypo
priority: normal
severity: normal
status: open
title: Use GetTickCount/GetTickCount64 instead of QueryPerformanceCounter for monotonic clock
versions: Python 3.3

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue14397>
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