Comment by nas

If you are using "httpx", it's likely caused by a reference cycle. I made a PR to fix it but the maintainers haven't applied it. :-( https://github.com/encode/httpx/pull/3733

The reference cycle httpx creates is kind of a worst-case scenario for the incremental GC issue. Both the generational (3.13 and older) and incremental GC are triggered by the net new "container" objects (objects that have references to others, like lists and not like ints and floats). The short summary is that you need to create more container objects before the incremental GC triggers. In the case of the httpx reference cycle, you have a relatively small number of container objects hanging on to a lot of memory, due the SSL context data (which is a big memory hog).

Reverting back to the generational GC was the wise thing to do, even though it's a bit scary to do in a bugfix release. The incremental GC works for most people but in the minority of cases it doesn't, it uses quite a lot more memory. I'm pretty sure with some additional tuning, the incremental GC would be fine too but it just didn't get that tuning. The generational GC has literal decades of real-world use (Guido merged my patch on Jun 2000, Tim Peters did a bunch of tuning after that to optimize it).