From: Guillaume Cottenceau <gc@mnc.ch>
To: Dave Cramer <pg@fastcrypt.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: increasing shared buffers: how much should be removed from OS filesystem cache?
Date: 04 Sep 2006 14:07:37 +0200
Message-ID: <87fyf7hm2e.fsf@meuh.mnc.lan> (raw)
In-Reply-To: <3743D7B4-2749-41C3-ADE1-39B86F7C98D4@fastcrypt.com>
References: <87veo7a5dn.fsf@meuh.mnc.lan>
<3743D7B4-2749-41C3-ADE1-39B86F7C98D4@fastcrypt.com>
Dave Cramer <pg 'at' fastcrypt.com> writes:
> Guillaume
>
> 1G is really not a significant amount of memory these days,
Yeah though we have 2G or 4G of RAM in our servers (and not only
postgres running on it).
> That said 6-10% of available memory should be given to an 8.0 or
> older version of postgresql
>
> Newer versions work better around 25%
>
> I'm not sure what you mean by mechanically removed from effective_cache
I mean that when you allocate more memory to applications, the
consequence is less memory the OS will be able to use for disk
cache.
> effective cache is really a representation of shared buffers plus OS
> cache
Are you sure the shared buffers should be counted in? As I
understand the documentation, they should not (as shared buffers
is allocated memory for the OS, not part of "kernel's disk
cache"):
Sets the planner's assumption about the effective size of the
disk cache (that is, the portion of the kernel's disk cache
that will be used for PostgreSQL data files). This is
measured in disk pages, which are normally 8192 bytes each.
The default is 1000.
--
Guillaume Cottenceau
Create your personal SMS or WAP Service - visit http://mobilefriends.ch/
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: gc@mnc.ch, pg@fastcrypt.com
Subject: Re: increasing shared buffers: how much should be removed from OS filesystem cache?
In-Reply-To: <87fyf7hm2e.fsf@meuh.mnc.lan>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox