Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to 3.6-rc5 on AMD chipsets - bisected

Alan Cox
2012-09-15T21:28:17Z

> Yes, postgress performs loads better with it's spinlocks, but due to
> that, it necessarily _hates_ preemption. How the is the scheduler
> supposed to know that any specific userland task _really_ shouldn't be
> preempted at any specific time, else bad things follow?

You provide a shared page for a process group so it can write hints to
which is kernel mapped so the scheduler can peek..

Alan