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    /* XXX doesn't mean anything anymore (the comment below is obsolete)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?

Yes, we can :)

Here is a patch.

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

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

PyThreadState.tick_counter field was added in 2002 by Armin Rigo: see issue #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?

> 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.

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 :-)

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