In response to "Khalid Baheyeldin" <kb@2bits.com>:

> On Nov 26, 2007 1:52 PM, Bill Moran < wmoran@potentialtech.com> wrote:
>
> > My point is:
> > a) Let me send you a tweaked postgresql.conf file and well find
> > out whether the performance difference is simply a matter of
> > untuned configuration and ...
>
> I will post them for all to see, maybe someone will point out something
> else.
>
> These are the non comment lines in postgresql.conf
>
> hba_file = '/etc/postgresql/8.2/main/pg_hba.conf'
> ident_file = '/etc/postgresql/8.2/main/pg_ident.conf'
> external_pid_file = '/var/run/postgresql/8.2-main.pid'
> listen_addresses = 'localhost'
> port = 5432
> max_connections = 100
> unix_socket_directory = '/var/run/postgresql'
> shared_buffers = 24MB
> max_fsm_pages = 153600
> log_line_prefix = '%t '
> stats_row_level = on
> autovacuum = on
> datestyle = 'iso, dmy'
> lc_messages = 'en_CA.UTF-8'
> lc_monetary = 'en_CA.UTF-8'
> lc_numeric = 'en_CA.UTF-8'
> lc_time = 'en_CA.UTF-8'

Oh yeah ... there's lots of room for improvement here.

How much RAM does this system have, and how much of it is "free"
memory during the test?

2GB of RAM.

Here is the output from free:

             total       used       free     shared    buffers     cached
Mem:       2060032    1813748     246284          0     576896     439828
-/+ buffers/cache:     797024    1263008
Swap:      3903712        260    3903452

And here is /proc/meminfo

MemTotal:      2060032 kB
MemFree:        245736 kB
Buffers:        577000 kB
Cached:         439912 kB
SwapCached:         16 kB
Active:         777476 kB
Inactive:       550212 kB
SwapTotal:     3903712 kB
SwapFree:      3903452 kB
Dirty:              96 kB
Writeback:           0 kB
AnonPages:      310812 kB
Mapped:          32764 kB
Slab:           457012 kB
SReclaimable:   425856 kB
SUnreclaim:      31156 kB
PageTables:       9352 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:   4933728 kB
Committed_AS:   526896 kB
VmallocTotal: 34359738367 kB
VmallocUsed:      2724 kB
VmallocChunk: 34359735611 kB

We can carve off some memory from cache and buffers (1016 MB combined).

Khalid ... are you willing to work with me to investigate this?
If not, I'll try to get my own test rig set up, but it probably
won't happen until the new year.

I am willing to, time permitting of course.

Off the top of my head, I'd start out with 2 things:
*) Bump shared_buffers to 1/4 the total memory on the system
*) "vacuum analyze" the database after the load but before
the perf test.

What do you mean after the load? You mean after loading data into the database but before running ab?

I'll look this over a bit and send you a recommended config file
later this evening.