Re: What happened to open_sync_without_odirect?

Josh Berkus wrote:
> On 1/15/11 4:30 PM, Bruce Momjian wrote:
> > Josh Berkus wrote:
> >> Last I remember, we were going to add this as an option. But I don't
> >> see a patch in the queue. Am I missing it? Was I supposed to write it?
> >
> > I don't know, but let me add that I am confused how this would look to
> > users. In many cases, kernels don't even support O_DIRECT, so what
> > would we do to specify this? What about just auto-disabling O_DIRECT if
> > the filesystem does not support it; maybe issue a log message about it.
>
> Yes, you *are* confused. The problem isn't auto-disabling, we already
> do that. The problem is *auto-enabling*; ages ago we made the
> assumption that if o_sync was supported, so was o_direct. We've now
> found out that's not true on all platforms.
>
> Also, test results show that even when supported, o_direct isn't
> necessarily a win. Hence, the additional fsync_method options.

I think it would be clear if we did not use o_direct for open_*sync, but
only for open_*sync_direct, so there was no auto-direct anything --- you
had to ask for it, and if we don't support it, you get an error. Right
now people aren't sure what they are getting.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +