[Python-checkins] peps: PEP 418: Try to fill the "Action on suspend" column

[victor.stinner]

http://hg.python.org/peps/rev/f0a64781e500
changeset:   4171:f0a64781e500
user:        Victor Stinner <victor.stinner at gmail.com>
date:        Fri Mar 30 04:21:11 2012 +0200
summary:
  PEP 418: Try to fill the "Action on suspend" column

files:
  pep-0418.txt |  29 +++++++++++++++++++++--------
  1 files changed, 21 insertions(+), 8 deletions(-)


diff --git a/pep-0418.txt b/pep-0418.txt
--- a/pep-0418.txt
+++ b/pep-0418.txt
@@ -186,18 +186,18 @@
 Table summarizing all monotonic clocks:
 
 
-=========================  ===============  ================  =================
+=========================  ===============  ================  ====================
 Name                       Resolution       Adjusted by NTP?  Action on suspend
-=========================  ===============  ================  =================
-CLOCK_MONOTONIC_RAW        1 ns             No                ?
-gethrtime                  1 ns             No                ?
+=========================  ===============  ================  ====================
+CLOCK_MONOTONIC_RAW        1 ns             No                Stopped
+gethrtime                  1 ns             No                Not stopped
 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                ?
-GetTickCount[64]()         1 ms - 15 ms     No                ?
+QueryPerformanceCounter()  0.3 ns - 5 ns    No                Accuracy issue
+GetTickCount[64]()         1 ms - 15 ms     No                Include suspend time
 timeGetTime()              1 ms - 15 ms     No                ?
-=========================  ===============  ================  =================
+=========================  ===============  ================  ====================
 
 mach_absolute_time
 ^^^^^^^^^^^^^^^^^^
@@ -212,6 +212,10 @@
 is always equals to one and does never fail, even if the function may fail
 according to its prototype.
 
+mach_absolute_time() stops during a sleep on PowerPC CPU, but not on Intel CPU:
+`Different behaviour of mach_absolute_time() on i386 / ppc
+<http://lists.apple.com/archives/PerfOptimization-dev/2006/Jul/msg00024.html>`_.
+
 mach_absolute_time() has a resolution of 1 nanosecond.
 
 CLOCK_MONOTONIC, CLOCK_MONOTONIC_RAW
@@ -319,6 +323,9 @@
 `GetTickCount() <http://msdn.microsoft.com/en-us/library/windows/desktop/ms724408(v=vs.85).aspx>`_,
 `GetTickCount64() <http://msdn.microsoft.com/en-us/library/windows/desktop/ms724411(v=vs.85).aspx>`_.
 
+The elapsed time retrieved by GetTickCount or GetTickCount64 includes time the
+system spends in sleep or hibernation.
+
 GetTickCount64() was added to Windows Vista and Windows Server 2008.
 
 The clock resolution is 1 millisecond. Its accuracy is usually around 15 ms. It
@@ -371,6 +378,9 @@
 is  ideally  suited  to  performance measurement tasks, where cheap, accurate
 interval timing is required.
 
+The linearity of gethrtime() is not preserved accross cpr suspend-resume cycle
+(`Bug 4272663 <http://wesunsolve.net/bugid/id/4272663>`_).
+
 Read the `gethrtime() manual page of Solaris 11
 <http://docs.oracle.com/cd/E23824_01/html/821-1465/gethrtime-3c.html#scrolltoc>`_.
 
@@ -455,13 +465,15 @@
 
 
 Windows: QueryUnbiasedInterruptTime
------------------------------------
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Gets the current unbiased interrupt time from the biased interrupt time and the
 current sleep bias amount. This time is not affected by power management sleep
 transitions.
 
-Is it monotonic?
+The elapsed time retrieved by the QueryUnbiasedInterruptTime function includes
+only time that the system spends in the working state.
+QueryUnbiasedInterruptTime() is not monotonic.
 
 QueryUnbiasedInterruptTime() was introduced in Windows 7.
 

-- 
Repository URL: http://hg.python.org/peps