Craig James <cjames(at)emolecules(dot)com> writes:
> ... This would result in a thousand
> or so Postgres connections on a machine with 32 CPUs.
> So the question is: do idle connections impact performance?
Yes. Those connections have to be examined when gathering snapshot
information, since you don't know that they're idle until you look.
So the cost of taking a snapshot is proportional to the total number
of connections, even when most are idle. This sort of situation
is known to aggravate contention for the ProcArrayLock, which is a
performance bottleneck if you've got lots of CPUs.
You'd be a lot better off with a pooler.
(There has been, and continues to be, interest in getting rid of this
bottleneck ... but it's a problem in all existing Postgres versions.)
regards, tom lane
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