Connections "Startup"

Hi.

I've noticed huge decrease in performance.
During this in htop i see a lot (200 - 300) of connections in state
"startup", each of them eats 3-3% of CPU time. This processes are not
visible in pg_stat_activity so i cant understand what they are doing, and i
cant kill them. I cant see the bottleneck in Disk IO to. The logs of
postgres says nothing to. I am confused.....
What can be the cause of huge amount of "startup" connections....
Maybe its better to start use connection pooler such as pgbouncer?
Thanks a lot.

PS.
Server config is:
2 * Intel Xeon 2660 CPU with 64 gigs of RAM.
Hardware RAID10.
Centos 6.6, PostgreSQL 9.1.2