Re: Problem with Out of Memory and no more connecction possible

Zitat von "AL-Temimi, Muthana" <muthana.al-temimi@tu-harburg.hamburg.de>:

> Hello admins,
>
> i have postgresql version  9.1 and those my configurations:
>
> max_connection=600
> shared_buffers=1024M
> work_mem=4M
> and all others parameters are default as delivered with postgresql.
>
> I installed on Suse Enterprice Linux Server and kernel_shxmem=
> 2GByte in the sysctl.conf, because if I put 1Gbyte postgresql will
> never started.
> The total RAM of the server is 8GB.
>
> But when the active connections reach 300 then we get out of memory
> and I checked the system through "top" and I got 7,8GB used from 8GB
> and started to swap also. At the same time there are no new
> connection possible.
>
> I have connection pool pgpool II in the front of and the everything
> with it till now OK. No problem in the system and works fine.
>
> Any help will be grateful
>
> Best Regards
>
> Muthana AL-Temimi
> M.Sc. Informations- und Kommunikations-Systeme

Hello,

have you check what is actually using the memory, eg. which percentage
for which processes? A typical postgresql process on my systems use ~
4M of non-shared memory, so with ~300 connections without pooling you
will have ~1,2G just for the processes running. Furthermore work_mem
is the limit of memory per sort which you can have many per connection
and query. Depending on your workload you can try reducing
shared_buffers and work_mem because Postgresql does not need much
shared_buffers but relies on the OS cache for most of the time and if
your sorts are rare or not that big/critical work_mem at 2M might also
be sufficient.

This is explained here in detail and there are also hints how to get
around if you really need a massive number of concurrent connections:

https://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server

Regards

Andreas