Hi Nicolas,

Here is the tunning I apply on my (5) servers  (Debian Wheezy)

1. create an empty file pg_memory.sh in /root directory and copy/paste the code below :

page_size=`getconf PAGE_SIZE`
phys_pages=`getconf _PHYS_PAGES`
shmall=`expr $phys_pages / 2`
shmmax=`expr $shmall \* $page_size`
echo kernel.shmmax = $shmmax
echo kernel.shmall = $shmall
echo 'Edit /etc/sysctl.conf and apply with : sysctl -p'

1. as root execute command :

bash pg_memory.sh

1. As notified in the script, copy/paste the result of  the script in /etc/sysctl.conf and execute command :

sysctl -p

1. You should now have these  parameters at the end of  sysctl.conf (this is an example):

kernel.shmmax = 2107961344
kernel.shmall = 514639

1. now install pgtune (apt-get install pgtune)
2. as root, execute command :

pgtune -i /etc/postgresql/9.1/main/postgresql.conf  -o pgsql.conf

1. This will duplicate the postgresql.conf and add some parameters at the end of the file.
2. Just open the new file (/root/pgsql.conf)
3. Copy/past the end of the file (lines with pgtune wizard as comment) in the real one ( /etc/postgresql/9.1/main/postgresql.conf ) . Backup it first!
4. Restart the server

Note : change path to postgresql.conf according to your OS/Server

PgTune will set parameters according to your system (OS, HD, Memory, etc).

I always trust pgtune and copy/paste "as is" in postgresql.conf. For now, all my servers are running well.

Hope this helps