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PEP 418: Add a table summarizing system clocks

This commit is contained in:
Victor Stinner 2012-03-30 23:16:06 +02:00
parent 5d38774ed5
commit 2e69f4914f
1 changed files with 36 additions and 5 deletions
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41
pep-0418.txt
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@ -185,20 +185,25 @@ Summary
Table summarizing all monotonic clocks: Table summarizing all monotonic clocks:
========================= =============== =============== ================ ==================== ========================= =============== =============== ================ ====================
Name Resolution Accuracy Adjusted by NTP? Action on suspend Name Resolution Accuracy Adjusted by NTP? Action on suspend
========================= =============== =============== ================ ==================== ========================= =============== =============== ================ ====================
CLOCK_MONOTONIC_RAW 1 ns ? No Stopped CLOCK_MONOTONIC_RAW 1 ns (*) No Stopped
gethrtime 1 ns ? No Not stopped gethrtime 1 ns (*) No Not stopped
CLOCK_HIGHRES 1 ns (*) No ?
CLOCK_MONOTONIC 1 ns (*) Yes on Linux Stopped on Linux
mach_absolute_time() 1 ns ? No ? mach_absolute_time() 1 ns ? No ?
CLOCK_HIGHRES 1 ns ? No ?
CLOCK_MONOTONIC 1 ns ? Yes on Linux Stopped on Linux
QueryPerformanceCounter() \- 0.3 ns - 5 ns No Accuracy issue QueryPerformanceCounter() \- 0.3 ns - 5 ns No Accuracy issue
GetTickCount[64]() 1 ms 1 ms - 15 ms No Include suspend time GetTickCount[64]() 1 ms 1 ms - 15 ms No Include suspend time
timeGetTime() 1 ms 1 ms - 15 ms No ? timeGetTime() 1 ms 1 ms - 15 ms No ?
========================= =============== =============== ================ ==================== ========================= =============== =============== ================ ====================
(*) The accurary of monotonic clocks depends on the operating system.
* Linux: ?
* FreeBSD: ?
* Solaris: ?
The resolution is the smallest difference between two timestamps supported by The resolution is the smallest difference between two timestamps supported by
the format used by the clock. For example, clock_gettime() uses a timespec the format used by the clock. For example, clock_gettime() uses a timespec
structure which has two integer fileds, tv_sec and tv_nsec, so the resolution structure which has two integer fileds, tv_sec and tv_nsec, so the resolution
@ -401,6 +406,32 @@ On Solaris, gethrtime() is the same as clock_gettime(CLOCK_MONOTONIC).
System time System time
----------- -----------
The system time can be set manually by the system administrator or
automatically by a NTP daemon.
Summary
^^^^^^^
Table summarizing all system time clocks:
========================= =============== ===============
Name Resolution Accuracy
========================= =============== ===============
CLOCK_REALTIME 1 ns (*)
GetSystemTimeAsFileTime 100 ns 1 ms - 15 ms
gettimeofday() 1 µs (*)
ftime() 1 ms (*)
time() 1 sec 1 sec
========================= =============== ===============
(*) The accurary of system clocks depends on the operating system.
* Windows: 1 ms - 15 ms
* Linux: ?
* Mac OS X: ?
* FreeBSD: ?
Windows: GetSystemTimeAsFileTime Windows: GetSystemTimeAsFileTime
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^