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From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Marc Rechté <marc4@rechte.fr>
To: pgsql-performance@lists.postgresql.org
Subject: Re: NUMA settings
Date: Tue, 05 May 2020 10:00:02 +0200
Message-ID: <60b780e9d34ea8a6be80193ec03ab16a160fd1eb.camel@cybertec.at> (raw)
In-Reply-To: <fd8fb5bd-eac6-7491-f1e8-3761387d9d03@rechte.fr>
References: <2d10f8ab-5fc6-a0a5-facf-68f35de95ea9@rechte.fr>
	<e4d2e9c66efebc14e7f13ed2c26171f7cd9f85ac.camel@cybertec.at>
	<20200504162042.3ctwpkg33trpyfdm@alap3.anarazel.de>
	<fd8fb5bd-eac6-7491-f1e8-3761387d9d03@rechte.fr>

On Tue, 2020-05-05 at 07:56 +0200, Marc Rechté wrote:
> Thanks for answers. Further readings make me think that we should *not* 
> start postgres with numactl --interleave=all: this may have counter 
> productive effect on backends anon memory (heap, stack). IMHO, what is 
> important is to use Huge Pages for shared buffers: they are allocated 
> (reserved) by the kernel at boot time and spread evenly on all nodes. On 
> top of that they never swap.
> 
> My (temp) conclusions are following:
>         vm.zone_reclaim_mode = 0
>         kernel.numa_balancing = 0 (still not sure with that choice)
>         wm.swappiness = 60 (default)
>         start postgres as usual (no numactl)

Thanks for sharing your insights.

I think that "vm.swappiness" should be 0.
PostgreSQL does its own memory management, any swapping by the kernel
would go against that.

Yours,
Laurenz Albe
-- 
Cybertec | https://www.cybertec-postgresql.com

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