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@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + It's impossible for everything to be true. +