Heikki Linnakangas wrote: > Jim C. Nasby wrote: > > On Thu, Dec 07, 2006 at 10:30:11AM +0000, Heikki Linnakangas wrote: > >> I've cut a new version of the GIT patch I posted earlier, and collected > >> all my dispersed todo-lists, post-it notes, performance results, > >> supplementary patches etc. I had to a single web-page: > >> > >> http://community.enterprisedb.com/git/ > >> > >> Perhaps the most interesting stuff apart from the patch itself is the > >> performance results. I've run some CPU bound tests to measure the extra > >> CPU overhead it causes. The CPU overhead is significant, the worst case > >> being a select of a single row from a table with just one integer column. > >> > >> However, the I/O savings are also the greatest for that same test case, > >> as the table grows and the test becomes I/O bound. I don't have the > >> numbers now, but earlier runs showed that the duration of the test was > >> roughly halved, which makes sense because the patch reduced the index > >> size so that it fit in memory, reducing the number of physical I/Os > >> required per select from 2 to 1. > >> > >> ISTM that if we want to enable GIT automatically, we need a way to > >> either reduce the CPU overhead, or have a smart heuristic to tune the > >> feature so that it's only enabled when it's beneficial. > > > > The maintain_cluster_order patch is useful by itself, and handles an > > existing TODO regarding pulling pages out of WAL in a specified order to > > maintain clustering. > > Pull pages out of WAL? That must be a typo...
I assume he meant FSM (free space map). -- Bruce Momjian [EMAIL PROTECTED] EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend