PEP 418: Fill "Include suspend" column of all tables
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Victor Stinner
parent
d78474c6f6
commit
58bb56489d
90
pep-0418.txt
90
pep-0418.txt
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@ -160,14 +160,11 @@ On Windows, ``QueryPerformanceCounter()`` is not used even though it
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has a better precision than ``GetTickCount()``. It is not reliable
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and has too many issues.
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.. note::
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``time.monotonic()`` detects ``GetTickCount()`` integer overflow
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(32 bits, roll-over after 49.7 days): it increases a delta by 2\
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:sup:`32` each time than an overflow is detected. The delta is
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stored in the process-local state and so the value of
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``time.monotonic()`` may be different in two Python processes
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running for more than 49 days.
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``time.monotonic()`` detects ``GetTickCount()`` integer overflow (32 bits,
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roll-over after 49.7 days): it increases a delta by 2\ :sup:`32` each time
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than an overflow is detected. The delta is stored in the process-local
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state and so the value of ``time.monotonic()`` may be different in two
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Python processes running for more than 49 days.
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time.perf_counter()
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@ -391,7 +388,8 @@ Glossary
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:Accuracy:
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Is the answer correct? Any clock will eventually <drift>; if a
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clock is intended to match <Civil Time>, it will need to be
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<adjusted> back to the "true" time.
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<adjusted> back to the "true" time. See also `Accuracy and precision
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<http://en.wikipedia.org/wiki/Accuracy_and_precision>`_.
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:Adjusted:
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Resetting a clock to the correct time. This may be done either
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@ -709,7 +707,7 @@ Monotonic clocks
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Name Resolution Adjusted Include sleep Include suspend
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========================= ========== =============== ============= ===============
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gethrtime() 1 ns No Yes Yes
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CLOCK_HIGHRES 1 ns No Yes ?
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CLOCK_HIGHRES 1 ns No Yes Yes
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CLOCK_MONOTONIC 1 ns Slewed on Linux Yes No
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CLOCK_MONOTONIC_COARSE 1 ns Slewed on Linux Yes No
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CLOCK_MONOTONIC_RAW 1 ns No Yes No
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@ -807,10 +805,6 @@ similar to CLOCK_MONOTONIC, less precise but faster.
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clock, even if the standard C library supports it. For example,
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CLOCK_MONOTONIC_RAW requires a kernel version 2.6.28 or later.
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.. note::
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``clock_gettime()`` requires to link the program against the rt
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(real-time) library.
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Windows: QueryPerformanceCounter
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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@ -963,16 +957,16 @@ On Solaris, gethrtime() is the same as clock_gettime(CLOCK_MONOTONIC).
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System time clocks
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------------------
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========================= =============== =============
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Name Resolution Include sleep
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========================= =============== =============
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CLOCK_REALTIME 1 ns Yes
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CLOCK_REALTIME_COARSE 1 ns Yes
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GetSystemTimeAsFileTime 100 ns Yes
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gettimeofday() 1 µs Yes
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ftime() 1 ms Yes
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time() 1 sec Yes
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========================= =============== =============
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========================= =============== ============= ===============
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Name Resolution Include sleep Include suspend
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========================= =============== ============= ===============
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CLOCK_REALTIME 1 ns Yes Yes
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CLOCK_REALTIME_COARSE 1 ns Yes Yes
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GetSystemTimeAsFileTime 100 ns Yes Yes
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gettimeofday() 1 µs Yes Yes
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ftime() 1 ms Yes Yes
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time() 1 sec Yes Yes
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========================= =============== ============= ===============
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Examples of clock precision on x86_64:
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@ -1025,15 +1019,15 @@ Process time
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The process time cannot be set. It is not monotonic: the clocks stop
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while the process is idle.
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========================= ========== =============
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Name Resolution Include sleep
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========================= ========== =============
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GetProcessTimes() 100 ns No
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CLOCK_PROCESS_CPUTIME_ID 1 ns No
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getrusage(RUSAGE_SELF) 1 µs No
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times() \- No
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clock() \- No (*)
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========================= ========== =============
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========================= ========== ============= ===============
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Name Resolution Include sleep Include suspend
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========================= ========== ============= ===============
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GetProcessTimes() 100 ns No No
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CLOCK_PROCESS_CPUTIME_ID 1 ns No No
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getrusage(RUSAGE_SELF) 1 µs No No
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times() \- No No
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clock() \- No (*) No
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========================= ========== ============= ===============
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(*) On Windows, clock() does include time elapsed during a sleep. It does not
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on other operating systems.
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@ -1081,6 +1075,10 @@ Python source code includes a portable library to get the process time (CPU
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time): `Tools/pybench/systimes.py
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<http://hg.python.org/cpython/file/tip/Tools/pybench/systimes.py>`_.
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See also the `QueryProcessCycleTime() function
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<http://msdn.microsoft.com/en-us/library/windows/desktop/ms684929(v=vs.85).aspx>`_
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(sum of the cycle time of all threads).
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Thread time
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-----------
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@ -1088,12 +1086,12 @@ Thread time
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The thread time cannot be set. It is not monotonic: the clocks stop
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while the thread is idle.
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========================= ==========
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Name Resolution
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========================= ==========
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CLOCK_THREAD_CPUTIME_ID 1 ns
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GetThreadTimes() 100 ns
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========================= ==========
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========================= ========== ============= ===============
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Name Resolution Include sleep Include suspend
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========================= ========== ============= ===============
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CLOCK_THREAD_CPUTIME_ID 1 ns Yes Epoch changes
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GetThreadTimes() 100 ns No ?
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========================= ========== ============= ===============
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Examples of clock precision on x86_64:
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@ -1105,16 +1103,22 @@ CLOCK_THREAD_CPUTIME_ID Linux 3.2 1 ns 6
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GetThreadTimes() Windows Seven 16 ms 16 ms
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========================= ================ =============== ===================
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CLOCK_THREAD_CPUTIME_ID returns a number of CPU cycles, not a number of
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seconds.
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Functions
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^^^^^^^^^
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* Windows: GetThreadTimes(). The precision can be read using
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GetSystemTimeAdjustment().
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GetSystemTimeAdjustment(). `MSDN documentation of GetThreadTimes()
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<http://msdn.microsoft.com/en-us/library/windows/desktop/ms683237(v=vs.85).aspx>`_.
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* clock_gettime(CLOCK_THREAD_CPUTIME_ID): Thread-specific CPU-time
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clock. The precision can be read using of clock_getres().
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See also pthread_getcpuclockid().
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See also the `QueryThreadCycleTime() function
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<http://msdn.microsoft.com/en-us/library/windows/desktop/ms684943(v=vs.85).aspx>`_
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(cycle time for the specified thread) and pthread_getcpuclockid().
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Windows: QueryUnbiasedInterruptTime
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@ -1130,6 +1134,10 @@ QueryUnbiasedInterruptTime() is not monotonic.
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QueryUnbiasedInterruptTime() was introduced in Windows 7.
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See also `QueryIdleProcessorCycleTime() function
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<http://msdn.microsoft.com/en-us/library/windows/desktop/ms684922(v=vs.85).aspx>`_
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(cycle time for the idle thread of each processor)
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Sleep, suspend and monotonic time
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=================================
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