gil-demo

Demo code for "It’s not the GIL it’s the Skill" talk at TechGym 2025

Preparation

Install python3.14 including the free-threaded version, as explained here.

Next, install the requirements for both version:

python3.14 -m pip install -r requirements.txt
python3.14t -m pip install -r requirements.txt

Examples

example-1

This example demonstrates a simple CPU-bound task (counting by incrementing a variable).

• This can be run single/mt/pool for n times.
• mt creates threads in the classic way, pool uses ThreadPoolExecutor (which will be used in next examples).
• Here we see significant improvement in mt comparing GIL to NOGIL.

python3.14 1-count.py mt 40
python3.14t 1-count.py mt 40

example-2

This example demonstrates a simple IO-bound task (crawling 3 URLs).

• This can be run single/mt/async for n times on n threads.
• Here we see the improvement in mt and async, with GIL.

python3.14 2-crawler.py single
python3.14 2-crawler.py mt
python3.14 2-crawler.py async

example-3

This example demonstrates the same simple CPU-bound task (counting by incrementing a variable).

• This can be run mt/mp for t times, using n threads/processes.
• mt for multithreading, mp for multiprocessing.
• Here we see significant improvement in mt (NOGIL) compared to mp in terms of memory.

python3.14t 3-count.py mp 60 200
python3.14 3-count.py mt 60 200
python3.14t 3-count.py mt 60 200

example-4

This example demonstrates CPU-bound and IO-bound tasks using a simple web server.

• There is a sync version using Flask and an async one using FastAPI.
• To run a controlled experiment both server apps are run using Granian.
• To run the client there are implementation for sync/async accordingly.
• Here we see clear advantage in IO-bound tasks for async over sync.

Flask App:

python3.14 -m granian --interface wsgi --workers 1 servers.sync_flask:app --port 8001
python3.14t -m granian --interface wsgi --workers 1 servers.sync_flask:app --port 8001
python3.14 4-api.py sync cpu
python3.14 4-api.py sync io

FastAPI App:

python3.14 -m granian --interface asgi --loop asyncio --workers 1 servers.async_fastapi:app --port 8002
python3.14t -m granian --interface asgi --loop asyncio --workers 1 servers.async_fastapi:app --port 8002
python3.14 4-api.py async cpu
python3.14 4-api.py async io