On Tue, 28 Jul 2009, Matthew Wakeling wrote:
Unlikely. Different threads on the same CPU core share their resources, so they don't need an explicit communication channel at all (I'm simplifying massively here). A real interconnect is only needed between CPUs and between different cores on a CPU, and of course to the outside world.
The question was "why are the new CPUs benchmarking so much faster than the old ones", and I believe that's mainly because the interconnection both between CPUs and between CPUs and memory are dramatically faster. The SMT improvements stack on top of that, but are in my opinion secondary. I base that on also seeing a dramatic improvement in memory transfer speeds on the new platform, which alone might even be sufficient to explain the performance boost. I'll break the two factors apart later to be sure though--all the regulars on this list know where I stand on measuring performance compared with theorizing about it.
-- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
