[issue44130] GIL Improvement

[Shreyan Avigyan]

Change by Shreyan Avigyan :


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resolution:  -> wont fix

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[issue44130] GIL Improvement

[Shreyan Avigyan]

Shreyan Avigyan  added the comment:

I suspected right. This was just CPU instability. In fact the patch is 1x-2x 
slower as reported by pyperf. Therefore I'm closing this issue. 

Though I'm working on another "yet to be failed attempt" to remove or rewrite 
the GIL to improve performance. Of course, any help would be appreciated there.

Repo - https://github.com/shreyanavigyan/pygilremove

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stage:  -> resolved
status: open -> closed

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[issue44130] GIL Improvement

[STINNER Victor]

STINNER Victor  added the comment:

> Mean +- std dev: 455 ms +- 13 ms

A single benchmark is useless without a reference. Please run the benchmark on 
unpatched python, then run it again on a patched Python, and compare results. 
You can store benchmark results using -o option. Example:

# Unpatched python
python pyperf_benchmark.py -o ref.json
# Patched python
python pyperf_benchmark.py -o new_gil.json
# Compare
python -m pyperf compare_to ref.json new_gil.json

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[issue44130] GIL Improvement

[Shreyan Avigyan]

Shreyan Avigyan  added the comment:

pyperf results -

Mean +- std dev: 455 ms +- 13 ms

Looks a little bit faster than current 3.11, 3.10 and 3.9 versions.

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[issue44130] GIL Improvement

[STINNER Victor]

STINNER Victor  added the comment:

> I attached the pyperf benchmark also.

Can you please provide pyperf_benchmark.py results?

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[issue44130] GIL Improvement

[Shreyan Avigyan]

Shreyan Avigyan  added the comment:

I attached the pyperf benchmark also.

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Added file: https://bugs.python.org/file50041/benchmark.py

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[issue44130] GIL Improvement

[Shreyan Avigyan]

Shreyan Avigyan  added the comment:

Sure

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[issue44130] GIL Improvement

[Christian Heimes]

Christian Heimes  added the comment:

The benchmark code has multiple issues. For example it uses a bad clock 
sources, time.time(). Could you please rewrite the benchmark to use 
https://pypi.org/project/pyperf/ ?

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[issue44130] GIL Improvement

[Shreyan Avigyan]

Shreyan Avigyan  added the comment:

> "That difference is 0.02 seconds, or about 1%, correct?"

I mistook 1.98 as 1.88 in my calculation. Sorry for that.

> The information is not very helpful to understand what you are doing. Please 
> provide your system specs (arch, platform, CPU spec, memory), the commands 
> you used to compile Python and the commands you used to get the numbers

My System is x86_64 Windows with 4 cores and 8 gigs of memory. I also tried it 
with my WSL1.

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[issue44130] GIL Improvement

[Shreyan Avigyan]

Shreyan Avigyan  added the comment:

Test suite passed and also I'm attaching the benchmark I used to measure. (This 
is the benchmark used by David Beazley in one of his famous GIL blog posts and 
talks.)

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Added file: https://bugs.python.org/file50040/benchmark.py

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[issue44130] GIL Improvement

[Eric V. Smith]

Eric V. Smith  added the comment:

"If it ran in 1.98 secs then the new patch would theoretically measure 
1.96 (original - 0.22)"

That difference is 0.02 seconds, or about 1%, correct?

I'm just trying to understand what we're measuring here.

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[issue44130] GIL Improvement

[Christian Heimes]

Christian Heimes  added the comment:

The information is not very helpful to understand what you are doing. Please 
provide your system specs (arch, platform, CPU spec, memory), the commands you 
used to compile Python and the commands you used to get the numbers

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[issue44130] GIL Improvement

[Shreyan Avigyan]

Shreyan Avigyan  added the comment:

I took the measurement like this. If it ran in 1.98 secs then the new patch 
would theoretically measure 1.96 (original - 0.22). The patch isn't very 
useful but it can sometimes be faster than the present code especially in debug 
mode.

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[issue44130] GIL Improvement

[Eric V. Smith]

Eric V. Smith  added the comment:

"there's an increase in speed by 0.22 or something like that"

0.22 what? Seconds? Percent? A factor of 0.22?

What are you measuring, and how are you measuring it?

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nosy: +eric.smith

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[issue44130] GIL Improvement

[Shreyan Avigyan]

Shreyan Avigyan  added the comment:

Forgot to do that. I'll report back with the test suite result.

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[issue44130] GIL Improvement

[Christian Heimes]

Christian Heimes  added the comment:

Does Python's unit test suite pass?

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nosy: +christian.heimes, pitrou, vstinner

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[issue44130] GIL Improvement

[Shreyan Avigyan]

Shreyan Avigyan  added the comment:

Instability is more likely. But I'll run the benchmark once more and see what 
is happening.

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[issue44130] GIL Improvement

[Shreyan Avigyan]

New submission from Shreyan Avigyan :

Today while working on an attempt to improve the GIL (either by modifying it or 
removing it) I noticed that in destroy_gil function first we unlock the mutex 
and then we set the gil->locked to -1 using _Py_atomic_store_explicit. 
Therefore the cycle is, "Unlock -> Atomic_Set_Value" which closely evaluates 
to, "Unlock -> Lock -> Set_Value -> Unlock"


I tweaked around a little and when I changed the cycle to, "Atomic_Set_Value -> 
Unlock" I noticed by running David Beazley's famous benchmarks that there's an 
increase in speed by 0.22 or something like that. I don't know if it's because 
of CPU instability or because of the tweak but it looks like an improvement. 
Should this patch be applied to cpython?

--
components: C API
messages: 393642
nosy: shreyanavigyan
priority: normal
severity: normal
status: open
title: GIL Improvement
type: performance
versions: Python 3.10, Python 3.11, Python 3.9

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