Add free threading scaling microbenchmarks

[colesbury]

Feature or enhancement

I've been using a simple script to help identify and track scaling bottlenecks in the free threading build. The benchmarks consists of patterns that ought to scale well, but haven't in the past, typically due to reference count contention or lock contention.

I think this is generally useful for people working on free-threading and would like to include it under Tools, perhaps as Tools/ftscalingbench/ftscalingbench.py.

Note that this is not intended to be a general multithreading benchmark suite, nor are the benchmarks intended to be representative of real-world workloads. The benchmarks are only intended to help identify and track scaling bottlenecks that occur in basic usage.

Here is the original script, I've since made some modifications:
https://github.com/colesbury/nogil-micro-benchmarks

Linked PRs

• gh-125985: Add free threading scaling micro benchmarks #125986
• gh-125985: Fix cmodule_function() scaling benchmark #128460