###############
Tuning Postgres
###############

Shared buffers
--------------

La dimensione degli sharedbuffers influenza notevolmente alcune operazioni di postgres. Si rimanda alla documentazione ufficiale
per come configurare opportunamente il sistema:

::
	
	http://www.postgresql.org/docs/9.1/static/kernel-resources.html


Estratto della documentazione: 

::
	
	
	The default maximum segment size is 32 MB, which is only adequate for very small PostgreSQL installations. 
	The default maximum total size is 2097152 pages. A page is almost always 4096 bytes except in unusual kernel 
	configurations with "huge pages" (use getconf PAGE_SIZE to verify). That makes a default limit of 8 GB, 
	which is often enough, but not always.
	
	The shared memory size settings can be changed via the sysctl interface. For example, to allow 16 GB:
	
		$ sysctl -w kernel.shmmax=17179869184
		$ sysctl -w kernel.shmall=4194304
	
	In addition these settings can be preserved between reboots in the file /etc/sysctl.conf. 
	Doing that is highly recommended.
	
	Ancient distributions might not have the sysctl program, but equivalent changes can be made by manipulating 
	the /proc file system:
	
		$ echo 17179869184 >/proc/sys/kernel/shmmax
		$ echo 4194304 >/proc/sys/kernel/shmall
	
	The remaining defaults are quite generously sized, and usually do not require changes.