Postgresql performance on Solaris

Hi,

I am getting poor performance from my postgresql (version 7.3.2 compiled
with gcc 2.95.2) database when running load tests on my web application.
The database works great until I get above 200 concurrent users. The
following query runtime will vary from:

explain analyze select TIMESTAMP, SPM_CONVSRCADDR,

SPM_CONVDSTADDR, SPM_CONVSRCPORT, SPM_CONVDSTPORT,

SPM_CONVPROTO, ACTION from FirewallLogs where TimeStamp>=1044939600000

and TimeStamp<=1047391020000 and spm_subid='462' and fqdn ='bs2(at)pcp' order
by

timestamp desc;

QUERY
PLAN

----------------------------------------------------------------------------
-----------------------------------------------------------------------

Sort (cost=3525.27..3527.49 rows=888 width=47) (actual time=55.65..56.16
rows=913 loops=1)

Sort Key: "timestamp"

-> Index Scan using firewalllogsindex on firewalllogs
(cost=0.00..3481.77 rows=888 width=47) (actual time=0.40..50.33 rows=913
loops=1)

Index Cond: ((fqdn = 'bs2(at)pcp'::character varying) AND ("timestamp"
>= 1044939600000::bigint) AND ("timestamp" <= 1047391020000::bigint))

Filter: (spm_subid = 462)

Total runtime: 57.36 msec

(6 rows)

to

QUERY
PLAN

----------------------------------------------------------------------------
-----------------------------------------------------------------------

Sort (cost=3525.27..3527.49 rows=888 width=47) (actual
time=2323.79..2324.31 rows=913 loops=1)

Sort Key: "timestamp"

-> Index Scan using firewalllogsindex on firewalllogs
(cost=0.00..3481.77 rows=888 width=47) (actual time=0.26..2318.11 rows=913
loops=1)

Index Cond: ((fqdn = 'bs2(at)pcp'::character varying) AND ("timestamp"
>= 1044939600000::bigint) AND ("timestamp" <= 1047391020000::bigint))

Filter: (spm_subid = 462)

Total runtime: 2325.62 msec

(6 rows)

NOTE: I am only performing select queries - no inserts, deletes or updates.

I am running postgresql on a SunFire v880 with 4 750MHz sparcv9 processors
with 8 Gig of RAM running solaris 8. I have 2 tables with 500,000 records
in each and both tables are indexed. I am connecting to the database
through JDBC using a pool of connections (tried pools of 50, 100, and 200
with similar results). When running the load tests, the cpu of the box is
always above 60% idle. I have run iostat and I am not seeing any problems
with io.

I have tried different size shared_buffers from 4100 to 64000, and I have
added the following to the /etc/system file:

set shmsys:shminfo_shmmax=0xffffffff

set shmsys:shminfo_shmmin=1

set shmsys:shminfo_shmmni=256

set shmsys:shminfo_shmseg=256

set semsys:seminfo_semmap=256

set semsys:seminfo_semmni=512

set semsys:seminfo_semmns=512

set semsys:seminfo_semmsl=32

I understand that this could be a problem with the kernel and not postgresql
but I am at a loss at what to change to get better performance out of the
database or the kernel.

Any help would be appreciated.