Postgres 10.3 On freebsd 10.3 is almost idle, disk i/o about 5-10%,
number running processes about 1-3, cpu about 90% idle, then we run a
i/o heavy job like "refresh materialized view", cpu & disk i/o still not
maxed out, all of a sudden the number of running processes increases to
about 250-300 for a second, which increases load averages that we
periodically poll to see if everything's alright. Why is that? Disk i/o
is far from being maxed out, the actual number of running processes is
really small.