From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alvaro Herrera <alvherre@commandprompt.com>
Cc: valiouk@yahoo.co.uk, pgsql-docs@postgresql.org, dx k9 <bitsandbytes88@hotmail.com>
Subject: Re: [ADMIN] shared_buffers and shmmax
Date: Wed, 17 Dec 2008 08:41:40 -0500 (EST)
Message-ID: <200812171341.mBHDfeK11281@momjian.us> (raw)
In-Reply-To: <20538.1229484675@sss.pgh.pa.us>
Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > Tom Lane wrote:
> >> If you're going to give a formula, why not just give a formula, eg
>
> > You mean like this:
> > http://momjian.us/tmp/pgsql/kernel-resources.html
>
> Yeah, more or less. A couple thoughts now that I see it worked out:
>
> * Combining the entries for max_connections and autovacuum_max_workers
> is probably just making it look more complicated than it needs to.
> How about two rows that just happen to have similar formulas, viz
>
> max_connections (1800 + 270 * max_locks_per_transaction) * max_connections
> autovacuum_max_workers (1800 + 270 * max_locks_per_transaction) * autovacuum_max_workers
>
> * The right-hand column header should be something like "Approximate
> shared memory bytes..." to avoid the impression that these formulas
> are meant to be exact.
>
> * If we do it like this then the left-hand column is really redundant,
> not to say wrong because the right-hand formulas depend on more than
> the single variable mentioned. How about something like
>
> Table 17-2 PostgreSQL shared memory usage
>
> Purpose Approximate number of bytes required (as of 8.3)
>
> Per-connection state (1800 + 270 * max_locks_per_transaction) * max_connections
> Autovacuum worker state (1800 + 270 * max_locks_per_transaction) * autovacuum_max_workers
> Prepared transaction state ...
> Shared disk buffers ...
> WAL buffers ...
> Fixed space requirements 770kB
OK, I updated it again:
http://momjian.us/tmp/pgsql/kernel-resources.html
I did change your left column wording because it could be interpreted as
something that changes during server execution, e.g. connections.
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
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-admin@postgresql.org
Cc: bruce@momjian.us, tgl@sss.pgh.pa.us, alvherre@commandprompt.com, bitsandbytes88@hotmail.com
Subject: Re: [ADMIN] shared_buffers and shmmax
In-Reply-To: <200812171341.mBHDfeK11281@momjian.us>
* 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