> While using huge pages whenever possible is the right solution and this should be enough for PostgreSQL, perhaps there are applications that cannot use huge pages and which are affected by the regression.

It will be more interesting to talk about those applications if and when they are found. And I wouldn't assume the solutions are limited to reverting this change, starting to use the new spinlock time-slice extension mechanism, and enabling huge pages.

It sounds like using 4K pages with 100G of buffer cache was just the thing that made this spinlock's critical section become longer than PostgreSQL's developers had seen before. So when trying to apply the solution to some hypothetical other software that is suddenly benchmarking poorly, I'd generalize from "enable huge pages" to "look for other differences between your benchmark configuration and what the software's authors tested on".