Re: performance regression with Linux 2.6.33 and glibc 2.12

The Friday 04 June 2010 15:59:05, Tom Lane wrote :
> Marc Cousin <cousinmarc@gmail.com> writes:
> > I hope I'm not going to expose an already known problem, but I couldn't
> > find it mailing list archives (I only found
> > http://archives.postgresql.org/pgsql- hackers/2009-12/msg01543.php).
>
> You sure this isn't the well-known "ext4 actually implements fsync
> where ext3 didn't" issue?
>
>             regards, tom lane

Everything is ext4. So I should have fsync working with write barriers on all
the tests.

I don't think this problem is of the same kind: I think it is really because
of O_DSYNC appearing on 2.6.33, and PostgreSQL using it by default now. If my
filesystem was lying to me about barriers, I should take no more performance
hit with open_datasync than with fdatasync, should I ?