Re: Increasing work_mem and shared_buffers on Postgres 9.2 significantly slows down queries

Two possibilities:

caching.  make sure to run each query several times in a row.

zone reclaim mode. If this has gotten turned on turn it back off.

How to tell:

sysctl -n vm.zone_reclaim_mode

Output should be 0.  If it's not, then add this to /etc/sysctl.conf:

vm.zone_reclaim_mode=0

and run: sudo sysctl -p

and see if that helps.