On 11/14/06, Jim C. Nasby <jim@xxxxxxxxx> wrote:
On Tue, Nov 14, 2006 at 09:17:08AM -0500, Merlin Moncure wrote: > On 11/14/06, Cosimo Streppone <cosimo@xxxxxxxxxxxx> wrote: > >I must say I lowered "shared_buffers" to 8192, as it was before. > >I tried raising it to 16384, but I can't seem to find a relationship > >between shared_buffers and performance level for this server. > > My findings are pretty much the same here. I don't see any link > between shared buffers and performance. I'm still looking for hard > evidence to rebut this point. Lower shared buffers leaves more > memory for what really matters, which is sorting. It depends on your workload. If you're really sort-heavy, then having memory available for that will be hard to beat. Otherwise, having a large shared_buffers setting can really help cut down on switching back and forth between the kernel and PostgreSQL. BTW, shared_buffers of 16384 is pretty low by today's standards, so that could be why you're not seeing much difference between that and 8192. Try upping it to 1/4 - 1/2 of memory and see if that changes things.
Can you think of a good way to construct a test case that would demonstrate the difference? What would be the 'best case' where a high shared buffers would be favored over a low setting? merlin
