[Python-checkins] peps: PEP 418: Add CLOCK_BOOTTIME and FreeBSD kern.timecounter.hardware sysctl
victor.stinner
python-checkins at python.org
Tue Apr 10 18:03:05 CEST 2012
http://hg.python.org/peps/rev/94793b715d71
changeset: 4211:94793b715d71
user: Victor Stinner <victor.stinner at gmail.com>
date: Tue Apr 10 13:58:42 2012 +0200
summary:
PEP 418: Add CLOCK_BOOTTIME and FreeBSD kern.timecounter.hardware sysctl
files:
pep-0418.txt | 29 ++++++++++++++++++++++++++++-
1 files changed, 28 insertions(+), 1 deletions(-)
diff --git a/pep-0418.txt b/pep-0418.txt
--- a/pep-0418.txt
+++ b/pep-0418.txt
@@ -260,7 +260,9 @@
* TSC (Time Stamp Counter): Historically, the TSC increased with every internal
processor clock cycle, but now the rate is usually constant (even if the
processor changes frequency) and usually equals the maximum processor
- frequency. The instructor RDTSC can be used to read this counter.
+ frequency. Multiple cores having different TSC values. Hibernation of system
+ will reset TSC value. The instructor RDTSC can be used to read this counter.
+ CPU frequency scaling for power saving.
* ACPI PMTMR (power management timer): ACPI 24-bit timer with a frequency
of 3.5 MHz (3,579,545 Hz). HPET can cause around 3 seconds of drift per day.
* Cyclone: The Cyclone timer uses a 32-bit counter on IBM Extended
@@ -788,6 +790,31 @@
<http://www.kernel.org/doc/man-pages/online/pages/man7/time.7.html>`_:
"overview of time and timers".
+FreeBSD timers
+--------------
+
+The sysctl program can be used to change the timecounter. For example::
+
+ # sysctl kern.timecounter.hardware="ACPI-fast"
+ kern.timecounter.hardware: HPET -> ACPI-fast
+
+
+Sleep, suspend and monotonic time
+=================================
+
+Linux
+-----
+
+On Linux, CLOCK_MONOTONIC and CLOCK_MONOTONIC_RAW includes time the system
+spends in sleep; but it does not include time spent in hibernation (ACPI S3
+mode). If the system clock jumps backward, CLOCK_MONOTONIC and
+CLOCK_MONOTONIC_RAW are not affected.
+
+Linux 2.6.39 and glibc 2.14 introduces a new clock: CLOCK_BOOTTIME.
+CLOCK_BOOTTIME is idential to CLOCK_MONOTONIC, except it also includes any time
+spent in suspend. Read also `Waking systems from suspend
+<http://lwn.net/Articles/429925/>`_ (March, 2011).
+
Sleeping
========
--
Repository URL: http://hg.python.org/peps
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