Re: Increasing RAM for more than 4 Gb. using postgresql - Mailing list pgsql-performance

From amrit@health2.moph.go.th
Subject Re: Increasing RAM for more than 4 Gb. using postgresql
Date
Msg-id 1105837366.41e9bd36c7de9@webmail.moph.go.th
Whole thread Raw
In response to Re: Increasing RAM for more than 4 Gb. using postgresql  (William Yu <wyu@talisys.com>)
Responses Re: Increasing RAM for more than 4 Gb. using postgresql  (William Yu <wyu@talisys.com>)
List pgsql-performance
> 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@data3 /]# cat < /proc/sys/kernel/shmmax
4000000000
shmall =
[root@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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