From: Bruce Momjian <bruce@momjian.us>
Message-Id: <200812152332.mBFNWaa26314@momjian.us>
Subject: Re: [ADMIN] shared_buffers and shmmax
In-Reply-To: <3bd4182ebf79bc4a171f08d03d2edb2f@biglumber.com>
To: Greg Sabino Mullane <greg@turnstep.com>
Date: Mon, 15 Dec 2008 18:32:36 -0500 (EST)
CC: pgsql-docs@postgresql.org, pgsql-hackers@postgresql.org
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I have added this TODO item:

	Rationalize the discrepancy between settings that use values in bytes
	and SHOW that returns the object count
	
        * http://archives.postgresql.org/pgsql-docs/2008-07/msg00007.php 

---------------------------------------------------------------------------

Greg Sabino Mullane wrote:
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> >> shared_buffers is in disk block size, typically 8K
> 
> > The table the OP is looking at (table 17.2 in the 8.3 docs) predates
> > the ability to specify shared_buffers in KB or MB instead of
> > number-of-buffers.  I agree it's not entirely obvious that what it
> > means is "multiply your setting in KB/MB by 8400/8192".  Anybody have
> > an idea how to clarify things?
> 
> Bite the bullet and start showing the buffer settings as a pure number of bytes
> everywhere, and get rid of the confusing '8kB' unit in pg_settings? Things like
> this don't help our cause:
> 
> test=# show shared_buffers;
>  shared_buffers
> ----------------
>  24MB
> (1 row)
> 
> test=# set temp_buffers = '24MB';
> SET
> 
> test=# show temp_buffers;
>  temp_buffers
> --------------
>  3072
> 
> test=# select name, setting from pg_settings where name ~ 'buffers';
>       name      | setting
> ----------------+---------
>  shared_buffers | 3072
>  temp_buffers   | 3072
>  wal_buffers    | 8
> 
> test=# show wal_buffers;
>  wal_buffers
> -------------
>  64kB
> 
> 
> --
> Greg Sabino Mullane greg@turnstep.com
> End Point Corporation
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-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +