Re: Performance tuning on FreeBSD

On Tue, 4 Mar 2008, Ivan Voras wrote:

> I'm curious about the math behind this - is ~4000 burst or sustained
> rate?

Average, which is not quite burst or sustained.  No math behind it, just
looking at a few samples of pgbench data on similar hardware.  A system
like this one is profiled at
http://www.kaltenbrunner.cc/blog/index.php?/archives/21-8.3-vs.-8.2-a-simple-benchmark.html
for example.

> For common BBU cache sizes (256M, 512M), filling that amount with data
> is pretty trivial.

I don't have any good numbers handy but I think the burst is >6000, you
only get that for a few seconds before all the caches fill and the rate
drops considerably.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD