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From: Alvaro Herrera <[email protected]>
To: Bruce Momjian <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: dx k9 <[email protected]>
Subject: Re: [ADMIN] shared_buffers and shmmax
Date: Mon, 15 Dec 2008 20:43:37 -0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

Bruce Momjian wrote:
> Tom Lane wrote:
> > [ redirecting to pgsql-docs ]
> > 
> > Valentin Bogdanov <[email protected]> writes:
> > >> From: dx k9 <[email protected]>
> > >> I'm trying to understand what the documentation means
> > >> by bytes per increment, what is the increment supposed to
> > >> be bytes, MB, or Kb.
> > 
> > > shared_buffers is in disk block size, typically 8K, at least that's what it is on Linux platforms. shmmax is quite simply in bytes.
> > 
> > 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?
> 
> I have updated the table title to be clearer.

I don't find it any clearer ... I think the missing clue is that if you
specify shared_buffers values in MB, you must divide the value by block
size.


> ***************
> *** 1119,1125 ****
>   
>         <row>
>          <entry>Fixed space requirements</>
> !        <entry>770 kB</entry>
>         </row>
>        </tbody>
>       </tgroup>
> --- 1119,1125 ----
>   
>         <row>
>          <entry>Fixed space requirements</>
> !        <entry>770 k</entry>
>         </row>
>        </tbody>
>       </tgroup>

This change is wrong, why did you do it?

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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