Re: fsync or fdatasync

On Tue, Sep 10, 2002 at 05:07:30PM -0400, Bruce Momjian wrote:
> > Anyway - I'm sure this is not enough to convince you, so I'll have to
> > set up a test instead. But not tonight.
>
> Again, that is a test case for only one OS.  It is helpful if we are
> going to start doing per-OS defaults, which is something we have talked
> about.

Oh; I assumed that was already the case.

> What would be great is a test program we can run on different
> OS's to find out which is more efficient.

Yes. Bare in mind though, that this is as much a filesystem issue as a
kernel issue. Two different filesystems on the same kernel may behave
very differently.

Of course one can't distribute seperate postgresql in different versions
optimized for differet filesystems, so perhaps it's just as good to
leave the default as it is and rather put some info (e.g. benchmarks for
different setting on different filesystems on different operating
systems, and the benchmark-script itself so people can do their own
tests). This way the default is allright, and users that need to tweek a
little extra have the info they need.


> Remember, in most cases, we are fsync'ing only one block so there is no
> _gathering_ to do.

Yes, I know you said so. But if that's the case for only most cases
there are some cases were it's not - so there is still some potential.



--
Ragnar Kjørstad