Re: BUG #17269: Why is virtual memory usage of PostgreSQL growing constantly?

At Tue, 9 Nov 2021 15:52:51 +0900, 菊池祐 <y.kikuchi0714@gmail.com> wrote in 
> Thank you for the useful information.
> I checked the number of connections, and I found there are about 3,000
> connections from clients now.
> I try to reduce it.
> 
> Let me check additionally.
> 1. This event that the virtual memory usage of PostgreSQL grows is due to a
> large number of connections.

I suspect so.  Since shared_buffers is 32GB, I suppose the remaining
96GB is consumed by backend processes.  By a quite-coarse estimation,
96GB per 3000 clients is 32MB per client. It looks like a bit large
but it depends on workload.  We could investigate the memory usage by
the clients but I'm not sure how to examine the memory usage of as
many as 3000 processes on Windows..

> 2. I didn't know that the moderate setting of max_connection is 100 to 200
> or 300 on
> a 128GB box. Where is it written in the PostgreSQL manual?

You can read a report from PGECons.  It is an annual report on a
benchmarking of PostgreSQL. It is not about Windows, but Linux on
128GB box. And not memory usage but performance against the number of
clients. But I expect it informative for you.

https://www.pgecons.org/wp-content/uploads/2021/05/1d9c4e24e6906bcf785905f243a62608.pdf

For example, with a simple workload made by pgbench, a server is
saturaged with 192 clients or 8000 tps of referenceing workload.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center