Thanks to Mr. Gruber for linking to this really interesting article about performance policies in the WebKit project:
We have a zero-tolerance policy for performance regressions. If a patch lands that regresses performance according to our benchmarks, then the person responsible must either back the patch out of the tree or drop everything immediately and fix the regression.
As we've been working towards Catalyst 5.8, I think this is a test we need to get in place to ensure that 5.8 can handle the same volume of request processing as the previous version.