pgsql: Doc: document possible need to raise kernel's somaxconn limit.

Doc: document possible need to raise kernel's somaxconn limit.

On fast machines, it's possible for applications such as pgbench
to issue connection requests so quickly that the postmaster's
listen queue overflows in the kernel, resulting in unexpected
failures (with not-very-helpful error messages).  Most modern OSes
allow the queue size to be increased, so document how to do that.

Per report from Kevin McKibbin.

Discussion: https://postgr.es/m/CADc_NKg2d+oZY9mg4DdQdoUcGzN2kOYXBu-3--RW_hEe0tUV=g@mail.gmail.com

Branch
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REL_10_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/1a9c3ffd64284041fed6e29b5c96d2cb3e0493a1

Modified Files
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doc/src/sgml/runtime.sgml | 16 ++++++++++++++++
1 file changed, 16 insertions(+)