8.2.1 on FreeBSD 5.4-RELEASE

Hi Guys.

We are running v8.1.2 on FreeBSD 5.4-RELEASE and the server is running
with above averege load.

When i do top i see alot of postmaster processes in "sbwait" state:

# uptime
4:29PM up 23 days, 20:01, 3 users, load averages: 3.73, 1.97, 1.71

# top
82808 pgsql 1 4 0 15580K 12008K sbwait 0 107:06 7.52%
postgres
82804 pgsql 1 4 0 15612K 12028K sbwait 0 106:13 7.08%
postgres
82806 pgsql 1 4 0 15576K 12008K sbwait 0 106:07 6.84%
postgres
82793 pgsql 1 4 0 15576K 12008K sbwait 0 106:05 6.54%
postgres
82801 pgsql 1 4 0 15612K 12032K sbwait 0 106:13 5.57%
postgres
82800 pgsql 1 4 0 15580K 12012K sbwait 0 105:45 4.88%
postgres
6613 pgsql 1 4 0 15612K 12020K sbwait 0 28:47 4.59%
postgres
82798 pgsql 1 4 0 15612K 12036K sbwait 0 106:10 4.49%
postgres
82799 pgsql 1 4 0 15612K 12036K sbwait 0 106:27 4.39%
postgres
82797 pgsql 1 4 0 15612K 12036K sbwait 1 106:23 4.25%
postgres
82748 pgsql 1 4 0 15564K 11864K sbwait 0 48:12 3.08%
postgres
82747 pgsql 1 4 0 15560K 11848K sbwait 0 47:58 3.08%
postgres
82749 pgsql 1 4 0 15564K 11868K sbwait 0 48:27 1.95%
postgres
82751 pgsql 1 4 0 15564K 11864K sbwait 0 48:14 1.66%
postgres
82739 pgsql 1 4 0 15564K 11868K sbwait 1 48:38 1.37%
postgres
82750 pgsql 1 4 0 15564K 11864K sbwait 0 48:07 1.27%
postgres

The server is not very busy, but it has more or less as many writes as
reads.

I have not seen more then 10-15 simultaneous queries.

Any idea why idle postmaster consume 3-5% CPU ?

This is a FreeBSD 5.4-RELEASE server with 2x3G Xeon CPUs, 2G memory,
RAID1 mirrored U320 drives.

Thanx
Paul