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

richard -rw- weinberger
2012-09-15T17:09:37Z

On Sat, Sep 15, 2012 at 6:36 PM, Mike Galbraith <efault@gmx.de> wrote:
>> Just using futex is unfortunately not the answer either.
>
> 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?

Why perform custom userspace spinlocks better than futex() based ones?
I thought we have futex() to get rid of the custom ones...
Makes futex() only sense when things like priority inheritance are needed?

--
Thanks,
//richard