i have postgresql version 9.1 and those my configurations:
max_connection=600
shared_buffers=1024M
work_mem=4M
and all others parameters are default as delivered with postgresql.
I installed on Suse Enterprice Linux Server and kernel_shxmem= 2GByte in the sysctl.conf, because if I put 1Gbyte postgresql will never started.
The total RAM of the server is 8GB.
But when the active connections reach 300 then we get out of memory and I checked the system through “top” and I got 7,8GB used from 8GB and started to swap also. At the same time there are no new connection possible.
I have connection pool pgpool II in the front of and the everything with it till now OK. No problem in the system and works fine.