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Comment by celeritascelery | Hacker News Reader

> That's the trade-off. Personally I think a single digit percentage slow-down of single-threaded code worth it.

Maybe. I would expect that 99% of python code going forward will still be single threaded. You just don’t need that extra complexity for most code. So I would expect that python code as a whole will have worse performance, even though a handful of applications will get faster.

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That's the mindset that leads to the funny result that `uv pip` is like 10x faster than `pip`.

Is it because Rust is just fast? Nope. For anything after resolving dependency versions raw CPU performance doesn't matter at all. It's writing concurrent PLUS parallel code in Rust is easier, doesn't need to spawn a few processes and wait for the interpreter to start in each, doesn't need to serialize whatever shit you want to run constantly. So, someone did it!

Yet, there's a pip maintainer who actively sabotages free-threading work. Nice.

> Yet, there's a pip maintainer who actively sabotages free-threading work.

Wow. Could you elaborate?

For anyone who hasn't used uv, I feel like 10x faster is an understatement. For cases where packages are already downloaded it's basically instant for any use case I have run into.

But the bar to parallelizing code gets much lower, in theory. Your serial code got 5% slower but has a direct path to being 50% faster.

And if there's a good free-threaded HTTP server implementation, the RPS of "Python code as a whole" could increase dramatically.

Is there any news from FastAPI folks and/or Gunicorn on their support?

You can do multiple processes with SO_REUSEPORT.

free-threaded makes sense if you need shared state.

Any webserver that wants to cache and reuse content cares about shared state, but usually has to outsource that to a shared in-memory database because the language can't support it.

And most web servers already need in memory databases for other things. And it’s a great design principle - use sharp focused tools.

As I recall, CPython has also been getting speed-ups lately, which ought to make up for the minor single-threaded performance loss introduced by free threading. With that in mind, the recent changes seem like an overall win to me.

It’s not either/or. The CPython speedups would be even better with the single threaded interpreter.

Nobody has suggested otherwise.

Sure but of those 99%, how many are performance-sensitive, CPU-bound (in Python not in C) applications? It's clearly some, not saying it's an easy tradeoff, but I assume the large majority of Python programs out there won't notice a slowdown.

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