crcastleAWS engineer reports PostgreSQL perf halved by Linux 7.0, fix may not be easy
https://lore.kernel.org/lkml/yr3inlzesdb45n6i6lpbimwr7b25kqk...
Its worth reading this follow-up LKML post by Andres Freund (who works on Postgres): https://lore.kernel.org/lkml/yr3inlzesdb45n6i6lpbimwr7b25kqk...
AIUI in that thread they're saying "0.51x" the perf on a 96-core arm64 machine and they're also saying they cannot reproduce it on a 96-core amd64 machine.
So it's not going to affect everybody both running PostgreSQL and upgrading to the latest kernel. Conditions seems to be: arm64, shitloads of core, kernel 7.0, current version of PostgreSQL.
That is not going to be 100% of the installed PostgreSQL DBs out there in the wild when 7.0 lands in a few weeks.
So perhaps this is a regression specifically in the arm64 code, or said differently maybe it’s a performance bug that has been there for a long time but covered up by the scheduler part that was removed?