Optimize pg_dump schema-only

Hi All,

I'm looking for advice for optimizing the pg_dump portion of "pg_upgrade
--link". Since this schema only dump can't take advantage of parallel
processing with jobs I'm looking for any preparation or configuration
settings that can improve speed.

9.2 to 9.6
CentOS 6/64bit
512GB

I see only one CPU of 32 doing anything and it's often at 100%. Disk IO
is minimal. Memory use varies but always plenty to spare.

During upgrade I'm running:
Only the upgrade - no other services
work_mem = 50MB
maintenance_work_mem = 2048MB
shared_buffers = 30GB
max_locks_per_transaction = 4096
autovacuum = off
autovacuum_freeze_max_age = 1500000000 #Had previous issues with
vacuum (to prevent wrap)

Truthfully, I thought I had increased work_mem until starting this
email. But increasing it is just a guess unless I get advice to do so
here. I'm at a knowledge level where I can only guess at the relevance
of vacuum, analyze or any other preparatory actions I can complete
before taking postgres offline for upgrade. My feeling is that the
bottleneck is the backend and not pg_dump. School me on that if needed
please.

Any advice and explanation is appreciated.

- Senor