Sometimes, the kernel’s no-regression rule may not have the desired
result. Andrea Arcangeli led a session at the 2019 Linux Storage,
Filesystem, and Memory-Management Summit to make the point that the recent
reversion of a fix after a performance regression was reported has led to
worse performance overall — with, as is his wont, a lot of technical
information to back up that point. With a wider understanding of what is at
stake here, he hopes, the reversion can itself be reverted.

Source: LWN.net – [$] Transparent huge pages, NUMA locality, and performance regressions