Skip site navigation (1) Skip section navigation (2)

Re: [ADMIN] shared_buffers and shmmax

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, valiouk(at)yahoo(dot)co(dot)uk, pgsql-docs(at)postgresql(dot)org, dx k9 <bitsandbytes88(at)hotmail(dot)com>
Subject: Re: [ADMIN] shared_buffers and shmmax
Date: 2008-12-15 23:43:37
Message-ID: 20081215234337.GP4067@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-adminpgsql-docspgsql-hackers
Bruce Momjian wrote:
> Tom Lane wrote:
> > [ redirecting to pgsql-docs ]
> > 
> > Valentin Bogdanov <valiouk(at)yahoo(dot)co(dot)uk> writes:
> > >> From: dx k9 <bitsandbytes88(at)hotmail(dot)com>
> > >> 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

In response to

Responses

pgsql-docs by date

Next:From: Bruce MomjianDate: 2008-12-15 23:46:00
Subject: Re: [ADMIN] shared_buffers and shmmax
Previous:From: Bruce MomjianDate: 2008-12-15 23:32:36
Subject: Re: [ADMIN] shared_buffers and shmmax

pgsql-hackers by date

Next:From: Bruce MomjianDate: 2008-12-15 23:46:00
Subject: Re: [ADMIN] shared_buffers and shmmax
Previous:From: Bruce MomjianDate: 2008-12-15 23:42:55
Subject: Re: Any reason not to return row_count in cursor of plpgsql?

pgsql-admin by date

Next:From: Bruce MomjianDate: 2008-12-15 23:46:00
Subject: Re: [ADMIN] shared_buffers and shmmax
Previous:From: Bruce MomjianDate: 2008-12-15 23:32:36
Subject: Re: [ADMIN] shared_buffers and shmmax

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group