This seems pretty straightforward. The issue mentions other calls in
mmapmodule that we could release the GIL on, but those are in methods
where we'd need to be careful to ensure that something sensible happens
if those are called concurrently. In prior art, note that python#12073
released the GIL for munmap.  In a toy benchmark, I see the speed up
you'd expect from doing this.

This seems pretty straightforward. The issue mentions other calls in mmapmodule that we could release the GIL on, but those are in methods where we'd need to be careful to ensure that something sensible happens if those are called concurrently. In prior art, note that #12073 released the GIL for munmap.  In a toy benchmark, I see the speedup you'd expect from doing this.

Automerge-Triggered-By: GH:gvanrossum