Tiny profiling info (Psyco #2)

[arigo]

BPO	617311
Nosy	@mwhudson, @gvanrossum, @arigo
Files	diff-2.2: context diff against the 2.2 branch diff-2.3: context diff for the cvs trunk diff: updated context diff for 2.3

^{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 = 'https://github.com/mwhudson'
closed_at = <Date 2002-11-08.12:56:53.000>
created_at = <Date 2002-10-01.23:20:54.000>
labels = ['interpreter-core']
title = 'Tiny profiling info (Psyco #2)'
updated_at = <Date 2002-11-08.12:56:53.000>
user = 'https://github.com/arigo'

bugs.python.org fields:

activity = <Date 2002-11-08.12:56:53.000>
actor = 'mwh'
assignee = 'mwh'
closed = True
closed_date = None
closer = None
components = ['Interpreter Core']
creation = <Date 2002-10-01.23:20:54.000>
creator = 'arigo'
dependencies = []
files = ['4606', '4607', '4608']
hgrepos = []
issue_num = 617311
keywords = ['patch']
message_count = 8.0
messages = ['41287', '41288', '41289', '41290', '41291', '41292', '41293', '41294']
nosy_count = 3.0
nosy_names = ['mwh', 'gvanrossum', 'arigo']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue617311'
versions = ['Python 2.3']

[arigo]

Psyco-friendly patch #2.

A very very small statistic-collecting patch.

pystate.h: added a field at the end of the
PyThreadStruct:

    int tick_counter;

ceval.c: eval_frame():

tstate->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 can be of interest to profilers
(like psyco.jit()).

We can safely guess that a single integer increment
every 100
interpreted bytecode instructions will go entierely
unnoticed
in any performance measure. [This is true for
pystone.py.]

[mwhudson]

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I see no harm in this.

Are you sure it's actually going to be useful, though?

[arigo]

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It is the only way I could work out so far that can
"predict" how much a function will be accelerated when run
under Psyco. This is a very precious indication for an
automatic Psyco-binder. The following table shows the
results with the various test functions of the
distribution's "test.py" file:

(fn name) (speed-up) (bytecode insns per second)
f1 106.00
2310545
f4 11.33
2819100
f5 12.08
2992445
f6 1.35
412022
f7 2.24
1331353
f7bis 10.29
1632296

The third column is '(tick_counter * check_interval) /
execution_time'. The correlation between the two columns is
admittedly not perfect, but still we can see that it was not
worthy to try and accelerate f6 because it didn't spend a
lot of time actually interpreting bytecodes.

Note that similar information could be obtained by setting a
line-tracing hook, counting not instructions but lines
(which is less precise but still a good approximation).
However, line tracing is *much* too slow for anything but
debugging usage.

[gvanrossum]

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I'd like to get this into 2.2.2. MWH, can you check it in?

[mwhudson]

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Done in

Include/pystate.h revision 2.18.16.1
Python/ceval.c revision 2.301.4.7

Armin, I don't know how you generated this patch, but it
would have been easier to apply if it had been rooted in the
"src" directory, like e.g.:

$ cvs diff Include/pystate.h Python/ceval.c > ~/diff

[arigo]

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Uploaded the 2.3 patch (this one cleanly generated -- for the
other one I just cat'ed two patches in one).

[arigo]

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Attached an updated diff for 2.3. This one doesn't have
Windows line endings and includes the initialization of
tick_counter to 0 that was added by Guido in the latest
2.2.2. (I thought it was unnecessary to initialize it to
anything because profilers would only be interested in
differences.)

[mwhudson]

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I got lazy and checked in all the psyco patches at once:

Include/pystate.h revision 2.21
Modules/pyexpat.c revision 2.76
Python/ceval.c revision 2.340
Python/pystate.c revision 2.22