clock_gettime/settime/getres: Add more clock identifiers

[vstinner]

BPO	14555
Nosy	@vstinner
Files	more_clock_ids.patch more_clock_ids.patch: Patch with Updated Clock Descriptions

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2015-03-18.11:02:04.756>
created_at = <Date 2012-04-11.22:29:17.386>
labels = ['type-feature', 'library']
title = 'clock_gettime/settime/getres: Add more clock identifiers'
updated_at = <Date 2015-03-18.11:02:04.754>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2015-03-18.11:02:04.754>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2015-03-18.11:02:04.756>
closer = 'vstinner'
components = ['Library (Lib)']
creation = <Date 2012-04-11.22:29:17.386>
creator = 'vstinner'
dependencies = []
files = ['25196', '30016']
hgrepos = []
issue_num = 14555
keywords = ['patch']
message_count = 8.0
messages = ['158084', '158085', '158167', '158227', '158237', '187260', '187793', '238413']
nosy_count = 2.0
nosy_names = ['vstinner', 'ransomedheart08']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'patch review'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue14555'
versions = []

[vstinner]

Python 3.3 supports the following clock identifiers:

• CLOCK_REALTIME
• CLOCK_MONOTONIC
• CLOCK_MONOTONIC_RAW
• CLOCK_HIGHRES
• CLOCK_PROCESS_CPUTIME_ID
• CLOCK_THREAD_CPUTIME_ID

Linux has more clocks:

• CLOCK_BOOTTIME
• CLOCK_REALTIME_COARSE
• CLOCK_MONOTONIC_COARSE
• CLOCK_BOOTTIME_ALARM
• CLOCK_REALTIME_ALARM

FreeBSD has more clocks:

• CLOCK_VIRTUAL
• CLOCK_UPTIME, CLOCK_UPTIME_FAST, CLOCK_UPTIME_PRECISE
• CLOCK_MONOTONIC_FAST, CLOCK_MONOTONIC_PRECISE
• CLOCK_REALTIME_FAST, CLOCK_REALTIME_PRECISE
• CLOCK_SECOND
• CLOCK_PROF

CLOCK_BOOTTIME is useful is you would like to handle system suspend for example.

[vstinner]

Extract of FreeBSD manpage of clock_gettime:

 The clock_id argument can be one of the following values: CLOCK_REALTIME,
 CLOCK_REALTIME_PRECISE, CLOCK_REALTIME_FAST for time that increments as a
 wall clock should; CLOCK_MONOTONIC, CLOCK_MONOTONIC_PRECISE,
 CLOCK_MONOTONIC_FAST which increments in SI seconds; CLOCK_UPTIME,
 CLOCK_UPTIME_PRECISE, CLOCK_UPTIME_FAST which starts at zero when the
 kernel boots and increments monotonically in SI seconds while the machine
 is running; CLOCK_VIRTUAL for time that increments only when the CPU is
 running in user mode on behalf of the calling process; CLOCK_PROF for
 time that increments when the CPU is running in user or kernel mode; or
 CLOCK_SECOND which returns the current second without performing a full
 time counter query, using in-kernel cached value of current second.

 The clock IDs CLOCK_REALTIME_FAST, CLOCK_MONOTONIC_FAST,
 CLOCK_UPTIME_FAST are analogs of corresponding IDs without _FAST suffix
 but do not perform a full time counter query, so their accuracy is one
 timer tick.  Similarly, CLOCK_REALTIME_PRECISE, CLOCK_MONOTONIC_PRECISE,
 CLOCK_UPTIME_PRECISE are used to get the most exact value as possible, at
 the expense of execution time.

[vstinner]

more_clock_ids.patch: add more clock identifiers. Don't add the following clocks: CLOCK_BOOTTIME_ALARM, CLOCK_REALTIME_ALARM, CLOCK_UPTIME_FAST, CLOCK_UPTIME_PRECISE, CLOCK_MONOTONIC_PRECISE, CLOCK_REALTIME_PRECISE.

The documentation should be improved :-/

[jimjjewett]

Any particular reason not to add those?

[vstinner]

Any particular reason not to add those?

I didn't find yet documentation of: CLOCK_BOOTTIME_ALARM, CLOCK_REALTIME_ALARM

For CLOCK_UPTIME_PRECISE, CLOCK_MONOTONIC_PRECISE, CLOCK_REALTIME_PRECISE: I don't know if there are useful. Are they different than the clocks without _PRECISE suffix?

For CLOCK_UPTIME_FAST, it's just that I forgot to add it :-)

[BreamoreBoy]

If nothing else the patch will need updating to show versionadded as 3.4 instead of 3.3.

[ransomedheart08]

I have added descriptions for CLOCK_BOOTTIME_ALARM and CLOCK_REALTIME_ALARM to the patch.

[vstinner]

I'm no more really interested to add these identifiers. So I just close the issue.