On Wed, 19 Dec 2007, Ron Mayer wrote:
Benchmarks I see[1] suggest that 8.1.2 scaled pretty reasonably to 16 cores (from the chart on page 9 in the link below). But yeah, 8.0 scaled to maybe 2 cores if you're lucky. :-) [1] http://www.pgcon.org/2007/schedule/attachments/22-Scaling%20PostgreSQL%20on%20SMP%20Architectures%20--%20An%20Update
Thank you, I was looking for that one but couldn't find it again. Note that those results are using a TPC-C variant, which is not the most CPU intensive of tests out there. It's certainly possible that an application that has more processing to do per transaction (I'm thinking something more in the scientific computing database realm) could scale even better.
While I'd expect the bang per buck to go down quite a bit beyond 8 cores, I know I haven't seen any data on what new systems running 8.3 are capable of, and extrapolating performance rules of thumb based on old data is perilous. Bottlenecks shift around in unexpected ways. In that Unisys example, they're running 32-bit single core Xeons circa 2004 with 4MB of *L3* cache and there's evidence that scales >16 processors. Current Xeons are considerably faster and you can get them with 4-8MB of *L2* cache.
What does that do to scalability? Beats me. Maybe since the individual CPUs are faster, you bottleneck on something else way before you can use 16 of them usefully. Maybe the much better CPU cache means there's less reliance on the memory bus and they scale better. It depends a lot on the CPU vs. memory vs. disk requirements of your app, which is what I was suggesting before.
-- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
