Re: How many threads/cores Postgres can utilise?

On Wed, Apr 28, 2010 at 3:15 AM, Piotr Kublicki <Piotr(dot)Kublicki(at)iop(dot)org> wrote:
>
> Dears,
>
> Sorry to be a royal pain, but I cannot find it anywhere in the
> documentation: how many threads/CPU cores Postgres v. 8.4 can utilise?
> We're thinking about installing Postgres on a virtual machine (RedHat 5
> 64-bits), however not sure how many CPUs can be wisely assigned, without
> wasting of resources. Can Postgres utilise multi-core/multi-threaded
> architecture in a reasonably extent?

Like Craig mentioned, each connection uses one core basically, and the
OS can use one or maybe two. But that means that on even moderately
busy servers 4 to 8 cores is very reasonable. On modern hardware it's
easy to get 6 or 8 cores pretty cheaply. 2P machines can have 12 or
16 cores for pretty cheap too.

Pgsql will get faster quickly as you increase parallel load to the
number of cores you have (assuming enough memory bw to keep up) and
slowly trail off as you add concurrent connections. If you're likely
to have hundreds of concurrent connections then adding more cores past
8 or 16 makes a lot of sense. AMD's magny cours look promising for
that role. You can build a 4P machine with 48 cores for a pretty
reasonable price.