On Fri, May 4, 2018 at 03:25:15PM -0400, Robert Haas wrote:
> On Fri, May 4, 2018 at 11:22 AM, Merlin Moncure <mmoncure@gmail.com> wrote:
> > If we are breaking 1:1 backend:session relationship, what controls
> > would we have to manage resource consumption?
>
> I mean, if you have a large number of sessions open, it's going to
> take more memory in any design. If there are multiple sessions per
> backend, there may be some possibility to save memory by allocating it
> per-backend rather than per-session; it shouldn't be any worse than if
> you didn't have pooling in the first place.
>
> However, I think that's probably worrying about the wrong end of the
> problem first. IMHO, what we ought to start by doing is considering
> what a good architecture for this would be, and how to solve the
> general problem of per-backend session state. If we figure that out,
> then we could worry about optimizing whatever needs optimizing, e.g.
> memory usage.
Yes, I think this matches my previous question --- if we are going to
swap out session state to allow multiple sessions to multiplex in the
same OS process, and that swapping has similar overhead to how the OS
swaps processes, why not just let the OS continue doing the process
swapping.
I think we need to first find out what it is that makes high session
counts slow. For example, if we swap out session state, will we check
the visibility rules for the swapped out session. If not, and that is
what makes swapping session state make Postgres faster, let's just find
a way to skip checking visibility rules for inactive sessions and get
the same benefit more simply.
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
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