Re: Setting Shared-Buffers

Hi Rafael,

On Thu, Jul 09, 2009 at 07:18:55PM -0300, Rafael Domiciano wrote:

> Today, I've upgraded a dedicated postgres server, from 2 Gb to 10 Gb.
> Everything gone well.
>
> But, I would like shared buffers to use at least 5 Gb of the total memory.
> Setting kernel.shmmax with 6291456000 (6000 Mb) is not working properly, the
> server is changing the value to a small one.
> So I can't set the shared buffers to the value that I want.
>
> Now, just momently, the server is running with only 2 Gb of shared buffers,
> but I want to use all the capacity of the server/memory.
>
> Can anyone help you,
>
> Linux Fedora Core 9
> postgres=# select version();
> version
> ---------------------------------------------------------------------------------------------------
> PostgreSQL 8.3.5 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 4.3.0
> 20080428 (Red Hat 4.3.0-8)

You cannot use more than 3.something GB of memory on a 32 bit system. A
single process is limited to IIRC 3.5 GB of address space on such
systems and shared memory is part of it's address space. If the server
supports such amounts of memory, it is likely that you may run a 64 bit
OS on it. (Note: You need a full dump/restore of the whole PostgreSQL DB
space if you switch to 64 bit.)

HTH,

Tino.

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