Message-ID: <47cb8d14-7288-945e-19d1-655b8117960e@joeconway.com>
Date: Thu, 6 Jul 2023 13:12:35 -0400
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To: kaido vaikla <kaido.vaikla@gmail.com>, pgsql-admin@postgresql.org
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From: Joe Conway <mail@joeconway.com>
Subject: Re: Invoke OOM killer
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On 7/6/23 12:27, kaido vaikla wrote:
> Hi,
> 
> How to invoke OOM killer for pg process?
> Some easy "hack" for test purpose.
> 
> OS
> Rocky Linux release 9.2 (Blue Onyx)
> pg
> 15.2

If you are running postgres under systemd, you can add a cgroup memory 
limit to the unit file. Something like (depending on cgroup version and 
systemd version the params might be slightly different -- cannot 
remember off the top of my head):
-------
MemoryAccounting=yes
MemoryMax=256M
-------
Don't forget to
-------
systemctl daemon-reload
systemctl restart postgresql@15
#or whatever version
-------


That will cause an OOM killer strike at 256M of total cgroup usage (all 
of the postgres processes combined).

 From there it is pretty easy to trigger by doing something like, e.g.
-------
-- attempt to create a ~500M string
select repeat('X', 500000000);
-------


-- 
Joe Conway
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com