Remove PyThreadState.tick_counter field

[vstinner]

BPO	19199
Nosy	@tim-one, @arigo, @jcea, @pitrou, @vstinner, @nedbat, @bitdancer, @serhiy-storchaka
Files	remove_tick_counter.patch

^{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 2013-10-09.12:53:18.286>
created_at = <Date 2013-10-08.21:18:41.108>
labels = []
title = 'Remove PyThreadState.tick_counter field'
updated_at = <Date 2013-10-09.23:11:22.534>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2013-10-09.23:11:22.534>
actor = 'jcea'
assignee = 'none'
closed = True
closed_date = <Date 2013-10-09.12:53:18.286>
closer = 'python-dev'
components = []
creation = <Date 2013-10-08.21:18:41.108>
creator = 'vstinner'
dependencies = []
files = ['32007']
hgrepos = []
issue_num = 19199
keywords = ['patch']
message_count = 8.0
messages = ['199256', '199257', '199259', '199261', '199262', '199263', '199279', '199293']
nosy_count = 9.0
nosy_names = ['tim.peters', 'arigo', 'jcea', 'pitrou', 'vstinner', 'nedbat', 'r.david.murray', 'python-dev', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue19199'
versions = ['Python 3.4']

[vstinner]

The C structure "PyThreadState" has a counter which is incremented in the bytecode evaluation loop (ceval.c), but never used.

    /* XXX doesn't mean anything anymore (the comment below is obsolete)
       => deprecate or remove? */
    /* tick_counter is incremented whenever the check_interval ticker
     * reaches zero. The purpose is to give a useful measure of the number
     * of interpreted bytecode instructions in a given thread.  This
     * extremely lightweight statistic collector may be of interest to
     * profilers (like psyco.jit()), although nothing in the core uses it.
     */
    int tick_counter;

Antoine Pitrou added the XXX comment when he merged the "new GIL" of Python 3.2.

Can we now remove it?

[pitrou]

Yes, we can :)

[vstinner]

Here is a patch.

I'm going to commit it in one week if nobody complains.

[bitdancer]

Should there be a mention in whats new in case any external tools are (still) looking at it and thinking it is meaningful?

[vstinner]

PyThreadState.tick_counter field was added in 2002 by Armin Rigo: see issue bpo-617311.
"A very very small statistic-collecting patch. (...) The purpose is to give a useful measure of the number of interpreted bytecode instructions in a given thread."

My patch will probably break the following module :-)
http://packages.ubuntu.com/fr/lucid/python-tickcount
"Python C extension module giving access to the internal tickcounter of python. This is useful for certain forms of profiling or performance analysis."
(But tickcounter was meanless since Python 3.2.)

The PyThreadState.tick_counter field was mentionned in the following question:
"Read how many Python instructions have been interpreted?"
http://stackoverflow.com/questions/16437487/read-how-many-python-instructions-have-been-interpreted

Should we add a new counter to count the number of executed Python instructions per thread? Or fix tick_counter?

Does we really need such counter or other profilers (cProfile) are enough?

[pitrou]

Should we add a new counter to count the number of executed Python
instructions per thread? Or fix tick_counter?

Let's just drop it. It's useless and nobody complained.

[arigo]

Better remove this field if its value is now useless anyway. If someone needs it again for a similar reason, he can contribute a patch like I did in 2002 :-)

[python-dev]

New changeset 3ce0102e4c1f by Victor Stinner in branch 'default':
Close bpo-19199: Remove PyThreadState.tick_counter field
http://hg.python.org/cpython/rev/3ce0102e4c1f