This improvement shaves off almost one minute on my machine for one of the longest functional test.
Before:
$ testr.py mempool_updatefr* Starting Bitcoin ABC functional tests mempool_updatefromblock.py started Running jobs: mempool_updatefromblock.py mempool_updatefromblock.py passed, Duration: 277 s
After:
$ testr mempool_updatefr* Starting Bitcoin ABC functional tests mempool_updatefromblock.py started Running jobs: mempool_updatefromblock.py mempool_updatefromblock.py passed, Duration: 219 s
This is a single commit from core#22707. The other commits still have a year worth of unbackported dependencies, and have a lower impact.
https://github.com/bitcoin/bitcoin/pull/22707/commits/86dbd54ae8a8f9c693c0ea67114bbff24a0754df