RE: Intermittent aggressive use of SWAP space by PostgreSQL despite availability of HUGE amounts of RAM for a small database.

Zaid … Thanks for your feedback. Pls recommend exact changes so that we can try it out.

Regards.

Mohammed M Siddiqui

From: Zaid Shabbir <zaidshabbir(at)gmail(dot)com>
Sent: Tuesday, July 30, 2024 9:16 AM
To: Mohammed Siddiqui <msiddiqui(at)net32(dot)com>
Cc: Aleksander Alekseev <aleksander(at)timescale(dot)com>; pgsql-bugs(at)lists(dot)postgresql(dot)org; Ken Sollars <Ken(at)net32(dot)com>; Matt Elliott <melliott(at)net32(dot)com>
Subject: Re: Intermittent aggressive use of SWAP space by PostgreSQL despite availability of HUGE amounts of RAM for a small database.

Hello Mohammed,

I reviewed your attached postgresql.conf file and observed some concerning points. As you mentioned you have 256 GB RAM with 100 GB database size. In your configuration file you use higher ranges as compared to your system resources like ..

shared_buffers = 120000MB
...
work_mem = 2048MB
...
maintenance_work_mem = 2048MB
...
effective_cache_size = 120000MB
...

max_connection = 3000

The above configuration looks too much as per your available system resources. It looks like you need some expert review to evaluate your system resources and configure the server accordingly.

Thanks & Regards
Zaid
Bitnine Global Inc.

On Thu, Jul 25, 2024 at 5:01 PM Mohammed Siddiqui <msiddiqui(at)net32(dot)com<mailto:msiddiqui(at)net32(dot)com>> wrote:
Configuration file is attached.

-----Original Message-----
From: Aleksander Alekseev <aleksander(at)timescale(dot)com<mailto:aleksander(at)timescale(dot)com>>
Sent: Tuesday, July 23, 2024 4:33 AM
To: pgsql-bugs(at)lists(dot)postgresql(dot)org<mailto:pgsql-bugs(at)lists(dot)postgresql(dot)org>
Cc: Mohammed Siddiqui <msiddiqui(at)net32(dot)com<mailto:msiddiqui(at)net32(dot)com>>; Ken Sollars <Ken(at)net32(dot)com<mailto:Ken(at)net32(dot)com>>; Matt Elliott <melliott(at)net32(dot)com<mailto:melliott(at)net32(dot)com>>
Subject: Re: Intermittent aggressive use of SWAP space by PostgreSQL despite availability of HUGE amounts of RAM for a small database.

Hi,

> We have been seeing intermittent aggressive use of SWAP space by PostgreSQL despite availability of HUGE amounts of free RAM. We have a 100 GB database with 256 GB RAM on the server so there is no shortage of RAM nor shortage in PostgreSQL buffer cache. Our swappiness setting is set to “1”.
> [...]

Please provide your postgresql.conf.

Also, why do you need a swap on such a setup? I seriously doubt that it serves any purpose.

--
Best regards,
Aleksander Alekseev