Postgres constant 30% CPU usage

Question

I recently migrated my Postgres database from Windows to CentOS 6.7. On Windows the database never used much CPU, but on Linux I see it using a constant ~30% CPU (using top). (4 core on machine)

Anyone know if this is normally, or why it would be doing this? The application seems to run fine, and as fast or faster than Windows.

Note, it is a big database, 100gb+ data, 1000+ databases.

I tried using Pgadmin to monitor the server status, but the server status hangs, and fails to run, error "the log_filename parameter must be equal"

Answer 1

With 1000 databases I expect vacuum workers and stats collector to spend a lot of time checking about what needs maintenance.

I suggest you to do two things

• raise the autovacuum_naptime parameter to reduce the frequency of checks
• put the stats_temp_directory on a ramdisk

You probably also set a high max_connections limit to allow your clients to use those high number of databases and this is another probable source of CPU load, due to the high number of 'slots' to be checked every time a backend has to synchronize with the others.