I have checked the transparent huge pages and zone reclaim mode and those are already disabled. As a trial and error method, I have reduced the shared buffer size from 8500MB to 3000MB. The CPU i/o wait is icreased a little. But the periodical over load has not occurred afterwards. (3 days passed without such situation). I shall report further developments. Thank you all for the great help. -- View this message in context: http://postgresql.nabble.com/Multi-processor-server-overloads-occationally-with-system-process-while-running-postgresql-9-4-tp5868474p5869047.html Sent from the PostgreSQL - performance mailing list archive at Nabble.com. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance