Re: fsync or fdatasync

On Tue, Sep 10, 2002 at 01:17:56PM -0400, Bruce Momjian wrote:
> Ragnar Kjørstad wrote:
> > On Tue, Sep 10, 2002 at 11:40:24AM -0400, Bruce Momjian wrote:
> > > We also use
> > > O_SYNC on open if it is available.
> >
> > Why? That will slow tings down...
>
> Actually, no, we are only O_SYNC'ing the WAL writes and sometimes that
> is faster because you are not writing then fsyncing, you are just
> writing.  The fdatasync only is better than O_SYNC when you are doing
> multiple WAL writes before an fdatasync and we normally don't do that.

OK, if it is a single write it makes sense. (But I doubt it makes much
of a difference - the overhead of a system call is almoust nothing
compared to a write to disk...)


--
Ragnar Kjørstad