Re: Increasing RAM for more than 4 Gb. using postgresql

From: amrit(at)health2(dot)moph(dot)go(dot)th
To: William Yu <wyu(at)talisys(dot)com>
Cc: PGsql-performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Increasing RAM for more than 4 Gb. using postgresql
Date: 2005-01-16 01:02:46
Message-ID: 1105837366.41e9bd36c7de9@webmail.moph.go.th
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> The theshold for using PAE is actually far lower than 4GB. 4GB is the
> total memory address space -- split that in half for 2GB for userspace,
> 2GB for kernel. The OS cache resides in kernel space -- after you take
> alway the memory allocation for devices, you're left with a window of
> roughly 900MB.

I set shammax =
[root(at)data3 /]# cat < /proc/sys/kernel/shmmax
4000000000
shmall =
[root(at)data3 /]# cat < /proc/sys/kernel/shmall
134217728
Is that ok for 4 Gb. mechine?

> Since the optimal state is to allocate a small amount of memory to
> Postgres and leave a huge chunk to the OS cache, this means you are
> already hitting the PAE penalty at 1.5GB of memory.
>
How could I chang this hitting?
Thanks
Amrit
Thailand

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