Modification de Shmax

http://www.postgresql.org/docs/9.1/static/runtime-config-resource.html

https://gist.github.com/1285137


 #!/bin/bash
 # http://archives.postgresql.org/pgsql-admin/2010-05/msg00285.php
 # Output lines suitable for sysctl configuration based
 # on total amount of RAM on the system. The output
 # will allow up to 50% of physical memory to be allocated
 # into shared memory.
 # On Linux, you can use it as follows (as root):
 #
 # ./shmsetup >> /etc/sysctl.conf
 # sysctl -p
 # Early FreeBSD versions do not support the sysconf interface
 # used here. The exact version where this works hasn't
 # been confirmed yet.
 
 page_size=`getconf PAGE_SIZE`
 phys_pages=`getconf _PHYS_PAGES`
 
 if [ -z "$page_size" ]; then
 echo Error: cannot determine page size
 exit 1
 fi
 
 if [ -z "$phys_pages" ]; then
 echo Error: cannot determine number of memory pages
 exit 2
 fi
 
 shmall=`expr $phys_pages / 2` 
 shmmax=`expr $shmall \* $page_size`

 echo \# Maximum shared segment size in bytes
 echo kernel.shmmax = $shmmax 
 echo \# Maximum number of shared memory segments in pages
 echo kernel.shmall = $shmall