slow "select count(*) from information_schema.tables;" in some cases

This happens typically when we are running many functions in parallel creating many temp tables and unlogged tables I think.

Here is a slow one:  

https://explain.depesz.com/s/tUt5 

and here is fast one :

https://explain.depesz.com/s/yYG4 

Here are my settings (the server has around 256 GB og memory) :

max_connections = 500

work_mem = 20MB

effective_cache_size = 96GB 

effective_io_concurrency = 256 

shared_buffers = 96GB

temp_buffers = 80MB

Any hints ?

Thanks .

Lars