On Thu, 2006-09-14 at 20:07 -0400, Dave Cramer wrote: > On 14-Sep-06, at 7:50 PM, Francisco Reyes wrote: > > > Dave Cramer writes: > > > >> personally, I'd set this to about 6G. This doesn't actually > >> consume memory it is just a setting to tell postgresql how much > >> memory is being used for cache and kernel buffers > > > > Gotcha. Will increase further. > > > >> regarding shared buffers I'd make this much bigger, like 2GB or more > > > > Will do 2GB on the weekend. From what I read this requires shared > > memory so have to restart my machine (FreeBSD). > > > > if I plan to give shared buffers 2GB, how much more over that > > should I give the total shared memory kern.ipc.shmmax? 2.5GB? > > I generally make it slightly bigger. is shmmax the size of the > maximum chunk allowed or the total ? That's the total on FreeBSD, per process. I think to allow more than 2GB there you may need a special compile option in the kernel. > > Also will shared buffers impact inserts/updates at all? > > I wish the postgresql.org site docs would mention what will be > > impacted. > Yes, it will, however not as dramatically as what you are seeing with > effective_cache > > > > Comments like: This setting must be at least 16, as well as at > > least twice the value of max_connections; however, settings > > significantly higher than the minimum are usually needed for good > > performance. > > > > Are usefull, but could use some improvement.. increase on what? All > > performance? inserts? updates? selects? > > > > For instance, increasing effective_cache_size has made a noticeable > > difference in selects. However as I talk to the developers we are > > still doing marginally in the inserts. About 150/min. > The reason is that with effective_cache the select plans changed (for > the better) ; it's unlikely that the insert plans will change. There aren't multiple INSERT plans (however, there could be a subselect or something, which would be planned separately). INSERT is INSERT. That means effective_cache_size will have zero effect on INSERT. Regards, Jeff Davis
