Re: wal_buffers

On Thu, Oct 06, 2005 at 08:56:31AM -0400, Ian Westmacott wrote:
> On Thu, 2005-10-06 at 02:39, Thomas F. O'Connell wrote:
> > The WAL Configuration chapter (25.2) has a pretty good discussion of
> > how wal_buffers is used:
> >
> > http://www.postgresql.org/docs/8.0/static/wal-configuration.html
> >
> > You might also take a look at Josh Berkus' recent testing on this
> > setting:
> >
> > http://www.powerpostgresql.com/
>
> Thanks; I'd seen the documentation, but not Josh Berkus'
> testing.
>
> For my part, I don't have a large number of concurrent
> connections, only one. But it is doing large writes,
> and XLogInsert is number 2 on the profile (with
> LWLockAcquire and LWLockRelease close behind). I suppose
> that is expected, but lead by the documentation I wanted
> to make sure XLogInsert always had some buffer space to
> play with.

If you are using a single connection, you are wasting lots of cycles
just waiting for the disk to spin. Were you to use multiple
connections, some transactions could be doing some useful work while
others are waiting for their transaction to be committed.

--
Alvaro Herrera http://www.amazon.com/gp/registry/5ZYLFMCVHXC
"I suspect most samba developers are already technically insane...
Of course, since many of them are Australians, you can't tell." (L. Torvalds)