Re: scaling multiple connections

mlw <markw(at)mohawksoft(dot)com> writes:
> I am getting a bit concerned about Postgres 7.1 performance with
> multiple connections. Postgres does not seem to scaling very
> well. Below there is a list of outputs from pgbench with different
> number of clients, you will see that postgres' performance in the
> benchmark drops with each new connection. Shouldn't the tps stay
> fairly constant?

There was quite a long thread about this in pghackers back in Jan/Feb
(or so). You might want to review it. One thing I recall is that
you need a "scaling factor" well above 1 if you want meaningful results
--- at scale factor 1, all of the transactions want to update the same
row, so of course there's no parallelism and a lot of lock contention.

The default WAL tuning parameters (COMMIT_DELAY, WAL_SYNC_METHOD, and
friends) are probably not set optimally in 7.1. We are hoping to hear
about some real-world performance results so that we can tweak them in
future releases. I do not trust benchmarks as simplistic as pgbench for
doing that kind of tweaking, however.

regards, tom lane