14 items tagged “gil”
2024
Supercharge the One Person Framework with SQLite: Rails World 2024 (via) Stephen Margheim shares an annotated transcript of the YouTube video of his recent talk at this year's Rails World conference in Toronto.
The Rails community is leaning hard into SQLite right now. Stephen's talk is some of the most effective evangelism I've seen anywhere for SQLite as a production database for web applications, highlighting several new changes in Rails 8:
... there are two additions coming with Rails 8 that merit closer consideration. Because these changes make Rails 8 the first version of Rails (and, as far as I know, the first version of any web framework) that provides a fully production-ready SQLite experience out-of-the-box.
Those changes: Ensure SQLite transaction default to IMMEDIATE mode to avoid "database is locked" errors when a deferred transaction attempts to upgrade itself with a write lock (discussed here previously, and added to Datasette 1.0a14 in August) and SQLite non-GVL-blocking, fair retry interval busy handler - a lower-level change that ensures SQLite's busy handler doesn't hold Ruby's Global VM Lock (the Ruby version of Python's GIL) while a thread is waiting on a SQLite lock.
The rest of the talk makes a passionate and convincing case for SQLite as an option for production deployments, in line with the Rails goal of being a One Person Framework - "a toolkit so powerful that it allows a single individual to create modern applications upon which they might build a competitive business".
Back in April Stephen published SQLite on Rails: The how and why of optimal performance describing some of these challenges in more detail (including the best explanation I've seen anywhere of BEGIN IMMEDIATE TRANSACTION) and promising:
Unfortunately, running SQLite on Rails out-of-the-box isn’t viable today. But, with a bit of tweaking and fine-tuning, you can ship a very performant, resilient Rails application with SQLite. And my personal goal for Rails 8 is to make the out-of-the-box experience fully production-ready.
It looks like he achieved that goal!
Free Threaded Python With Asyncio.
Jamie Chang expanded my free-threaded Python experiment from a few months ago to explore the interaction between Python's asyncio and the new GIL-free build of Python 3.13.
The results look really promising. Jamie says:
Generally when it comes to Asyncio, the discussion around it is always about the performance or lack there of. Whilst peroformance is certain important, the ability to reason about concurrency is the biggest benefit. [...]
Depending on your familiarity with AsyncIO, it might actually be the simplest way to start a thread.
This code for running a Python function in a thread really is very pleasant to look at:
result = await asyncio.to_thread(some_function, *args, **kwargs)
Jamie also demonstrates asyncio.TaskGroup, which makes it easy to execute a whole bunch of threads and wait for them all to finish:
async with TaskGroup() as tg:
for _ in range(args.tasks):
tg.create_task(to_thread(cpu_bound_task, args.size))
Free-threaded CPython is ready to experiment with! The Python 3.13 beta releases that include a "free-threaded" version that removes the GIL are now available to test! A team from Quansight Labs, home of the PyData core team, just launched py-free-threading.github.io to help document the new builds and track compatibility with Python's larger ecosystem.
Free-threading mode will not be enabled in Python installations by default. You can install special builds that have the option enabled today - I used the macOS installer and, after enabling the new build in the "Customize" panel in the installer, ended up with a /usr/local/bin/python3.13t binary which shows "Python 3.13.0b3 experimental free-threading build" when I run it.
Here's my TIL describing my experiments so far installing and running the 3.13 beta on macOS, which also includes a correction to an embarrassing bug that Claude introduced but I failed to catch!
gh-116167: Allow disabling the GIL with PYTHON_GIL=0 or -X gil=0. Merged into python:main 14 hours ago. Looks like the first phase of Sam Gross’s phenomenal effort to provide a GIL free Python (here via an explicit opt-in) will ship in Python 3.13.
2023
A Steering Council notice about PEP 703 (Making the Global Interpreter Lock Optional in CPython) (via) Huge news concerning the nogil research fork of Python: “It’s clear that the overall sentiment is positive, both for the general idea and for PEP 703 specifically. The Steering Council is also largely positive on both. We intend to accept PEP 703, although we’re still working on the acceptance details.”
The Python Language Summit 2023: Making the Global Interpreter Lock Optional. Extremely informative update covering Sam Gross’s python-nogil proposal from this year’s language summit at PyCon.
Sam has been working hard on his fork for the past year, and now has it rebased for Python 3.12. If his PEP is accepted it could end up as an optional compile-time build in time for Python 3.13.
“The plan for nogil remains that it would be enabled via a compile-time flag, named --disable-gil. Third-party C extensions would need to provide separate wheels for GIL-disabled Python.”
Real Multithreading is Coming to Python—Learn How You Can Use It Now (via) Martin Heinz provides a detailed tutorial on trying out the new Per-Interpreter GIL feature that’s landing in Python 3.12, which allows Python code to run concurrently in multiple threads by spawning separate sub-interpreters, each with their own dedicated GIL.
It’s not an easy feature to play with yet! First you need to compile Python yourself, and then use APIs that are generally only available to C code (but should hopefully become available to Python code itself in Python 3.13).
Martin’s workaround for this is ingenious: it turns out the Python test.support package provides utility functions to help write tests against interpreters, and Martin shows how to abuse this module to launch, run and cleanup interpreters using regular Python code.
He also demonstrates test.support.interpreters.create_channel(), which can be used to create channels with receiver and sender ends, somewhat similar to Go.
My strong hunch is that the GIL does not need removing, if a) subinterpreters have their own GILs and b) an efficient way is provided to pass (some) data between subinterpreters lock free and c) we find good patterns to make working with subinterpreters work.
2022
Weeknotes: Datasette Lite, nogil Python, HYTRADBOI
My big project this week was Datasette Lite, a new way to run Datasette directly in a browser, powered by WebAssembly and Pyodide. I also continued my research into running SQL queries in parallel, described last week. Plus I spoke at HYTRADBOI.
[... 1,434 words]Testing Datasette parallel SQL queries in the nogil/python fork. As part of my ongoing research into whether Datasette can be sped up by running SQL queries in parallel I’ve been growing increasingly suspicious that the GIL is holding me back. I know the sqlite3 module releases the GIL and was hoping that would give me parallel queries, but it looks like there’s still a ton of work going on in Python GIL land creating Python objects representing the results of the query.
Sam Gross has been working on a nogil fork of Python and I decided to give it a go. It’s published as a Docker image and it turns out trying it out really did just take a few commands... and it produced the desired results, my parallel code started beating my serial code where previously the two had produced effectively the same performance numbers.
I’m pretty stunned by this. I had no idea how far along the nogil fork was. It’s amazing to see it in action.
[history] When I tried this in 1996 (via) “I removed the GIL back in 1996 from Python 1.4...” is the start of a fascinating (supportive) comment by Greg Stein on the promising nogil Python fork that Sam Gross has been putting together. Greg provides some historical context that I’d never heard before, relating to an embedded Python for Microsoft IIS.
2021
The GIL and its effects on Python multithreading (via) Victor Skvortsov presents the most in-depth explanation of the Python Global Interpreter Lock I’ve seen anywhere. I learned a ton from reading this.
2009
jessenoller.com—python magazine. Jesse Noller has been sharing his articles originally published in Python Magazine. Topics include SSH programming with Paramiko, context managers and the with statement and an excellent explanation of Python’s threading support and the global interpreter lock.
2008
What’s New in Python 2.6. The new multiprocessing package looks pretty useful, especially as it provides a way to work around Python’s GIL.