Feedback-ID: ie3de48e3:Fastmail
Date: Wed, 25 Jun 2025 14:42:49 +0200
From: =?utf-8?Q?=C3=81lvaro?= Herrera <alvherre@kurilemu.de>
To: Tomas Vondra <tomas@vondra.me>
Cc: Jakub Wartak <jakub.wartak@enterprisedb.com>,
	Christoph Berg <myon@debian.org>,
 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>,
	Andres Freund <andres@anarazel.de>,
 Tomas Vondra <tomas.vondra@postgresql.org>,
	pgsql-hackers@lists.postgresql.org
Subject: Re: pgsql: Introduce pg_shmem_allocations_numa view
Message-ID: <202506251242.3xobc3f4rthr@alvherre.pgsql>
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On 2025-Jun-25, Tomas Vondra wrote:

> Not sure. I thought NUMA doesn't matter very much on 32-bit systems too,
> exactly because those systems tend to use small amounts of memory. But
> then while investigating this issue I realized even rpi5 has NUMA, in
> fact it has a whopping 8 nodes:
> 
> debian@raspberry-32:~ $ numactl --hardware
> available: 8 nodes (0-7)

Interesting.  Mine only shows a single node.

alvherre@amras:~ $ uname -a
Linux amras 6.12.25+rpt-rpi-2712 #1 SMP PREEMPT Debian 1:6.12.25-1+rpt1 (2025-04-30) aarch64 GNU/Linux
alvherre@amras:~ $ sudo numactl --hardware
available: 1 nodes (0)
node 0 cpus: 0 1 2 3
node 0 size: 8051 MB
node 0 free: 202 MB
node distances:
node   0 
  0:  10 
alvherre@amras:~ $ sudo lscpu 
Architecture:             aarch64
  CPU op-mode(s):         32-bit, 64-bit
  Byte Order:             Little Endian
CPU(s):                   4
  On-line CPU(s) list:    0-3
Vendor ID:                ARM
  Model name:             Cortex-A76
    Model:                1
    Thread(s) per core:   1
    Core(s) per cluster:  4
    Socket(s):            -
    Cluster(s):           1
    Stepping:             r4p1
    CPU(s) scaling MHz:   62%
    CPU max MHz:          2400.0000
    CPU min MHz:          1500.0000
    BogoMIPS:             108.00
    Flags:                fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp
                           asimdhp cpuid asimdrdm lrcpc dcpop asimddp
[...]
NUMA:                     
  NUMA node(s):           1
  NUMA node0 CPU(s):      0-3


Did you enable something special on it maybe?

... Oh, I found this:
https://www.jeffgeerling.com/blog/2024/numa-emulation-speeds-pi-5-and-other-improvements
Sounds like you have this in your system and I don't in mine.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/