Re: Synchronous replication

On 14/07/10 09:50, Fujii Masao wrote:
> TODO
> ----
> The patch have no features for performance improvement of synchronous
> replication. I admit that currently the performance overhead in the
> master is terrible. We need to address the following TODO items in the
> subsequent CF.
>
> * Change the poll loop in the walsender
> * Change the poll loop in the backend
> * Change the poll loop in the startup process
> * Change the poll loop in the walreceiver

I was actually hoping to see a patch for these things first, before any 
of the synchronous replication stuff. Eliminating the polling loops is 
important, latency will be laughable otherwise, and it will help the 
synchronous case too.

> * Perform the WAL write and replication concurrently
> * Send WAL from not only disk but also WAL buffers

IMHO these are premature optimizations that we should not spend any 
effort on now. Maybe later, if ever.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com