I suggest to post-pone this optimization to Python 3.8. Faster list.sort() is nice to have, but I'm not sure that it's a killer feature that will make everybody move to Python 3.7. It can wait for 3.8.

No core dev took the lead on this non-trivial issue, and IMHO it's getting too late for 3.7.

It see that Serhiy started to review the change and asked for more benchmarks. Serhiy would be a good candidate to drive such work, but sadly he seems to be busy these days...

While such optimization is nice to have, we should be careful to not introduce a performance regressions on some cases. I read quickly the issue, and I'm not sure that it was fully carefully reviewed and tested yet. Sorry, I only read it quickly, ignore me if I'm wrong.

Well, if someone wants to take the responsability of pushing this right now, it's up to you :-)