Différence entre PG 8.4 et 9.3 sur la configuration

Hello les amateurs d'éléphants !

Je cherche à vérifier les performances de PG 9.3 par rapport à notre
actuel 8.4 (intégration de CSV identiques, requêtes identiques, etc).
Pareil pour la conf. Mais les perfs en 9,3beta1 ne sont pas trés
bonnes. On suspecte la conf ou la VM.

Savez vous si la conf à changer pour la 9 sur la gestion des perfs ?
Si oui, avez vous des pointeurs intéressants ?

Merci d'avance.

Voici cette conf :

## Basic
fsync = on
autovacuum = off
synchronous_commit = off
lc_messages = 'C'
lc_monetary = 'C'
lc_numeric = 'C'
lc_time = 'C'
data_directory = '/srv/postgresql/9.3/main'
hba_file = '/opt/conf/postgresql/9.3/main/pg_hba.conf'
ident_file = '/opt/conf/postgresql/9.3/main/pg_ident.conf'
external_pid_file = '/var/run/postgresql/9.3-main.pid'
unix_socket_directories = '/var/run/postgresql/'

## Advance
shared_buffers = {{20|percent_of_ram}}MB
effective_cache_size = {{60|percent_of_ram}}MB
wal_buffers = {{0.1|percent_of_ram}}kB
temp_buffers = {{0.5|percent_of_ram}}MB
work_mem = {{4|percent_of_ram}MB
maintenance_work_mem = {{not_below(8, to_M(percent_of_ram(0.25)))}}MB
wal_writer_delay = 2000ms
max_stack_depth = 6MB
max_connections = 64
max_prepared_transactions = 0
max_locks_per_transaction = 2048
checkpoint_segments = 64
checkpoint_timeout = 3600
default_statistics_target = 300

## Advance (exemple avec 8Go de RAM)
shared_buffers = 1601MB
effective_cache_size = 4803MB
wal_buffers = 8005kB
temp_buffers = 40MB
work_mem = 320MB
maintenance_work_mem = 20MB
wal_writer_delay = 2000ms
max_stack_depth = 6MB
max_connections = 64
max_prepared_transactions = 0
max_locks_per_transaction = 2048
checkpoint_segments = 64
checkpoint_timeout = 3600
default_statistics_target = 300

## Profiling
logging_collector = on
log_min_duration_statement = 0
log_line_prefix = '%t [%p]: [%l-1] '
log_checkpoints = on
log_connections = on
log_disconnections = on
log_lock_waits = on
log_temp_files = 0
log_directory = '/var/log/postgresql'
log_filename = 'postgresql-9.3-main-full.log'
log_truncate_on_rotation = off

--
Sebastien Douche <sdouche(at)gmail(dot)com>
Twitter: @sdouche / G+: +sdouche