Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1uo2YV-00FXY9-KP for pgsql-performance@arkaria.postgresql.org; Mon, 18 Aug 2025 16:17:57 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.94.2) (envelope-from ) id 1uo2YV-000Q1h-2C for pgsql-performance@arkaria.postgresql.org; Mon, 18 Aug 2025 16:17:55 +0000 Received: from makus.postgresql.org ([2001:4800:3e1:1::229]) by malur.postgresql.org with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1uo2YU-000Q1Z-OL for pgsql-performance@lists.postgresql.org; Mon, 18 Aug 2025 16:17:55 +0000 Received: from mail1.dalibo.net ([51.159.93.128] helo=mail.dalibo.com) by makus.postgresql.org with smtp (Exim 4.96) (envelope-from ) id 1uo2YS-000Ur0-32 for pgsql-performance@lists.postgresql.org; Mon, 18 Aug 2025 16:17:54 +0000 Received: from [192.168.0.7] (5-49-10-71.hfc.dyn.abo.bbox.fr [5.49.10.71]) by mail.dalibo.com (Postfix) with ESMTPSA id 3335726307; Mon, 18 Aug 2025 18:17:51 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=dalibo.com; s=a; t=1755533871; bh=7vJrOEPgvnjofU2xe5K5FI8np4wsl9OymNLT8a+YECs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=H+YiWlRPYLmqce1mkwvB1aL1gAPP4iV40suBjLV/2jLTyMVyE4cFUFHqc1NkTPMFw BeVY2aur65ZS+8CBcs1L/jK5IKVFEvYOySQvkDfdwKKy7nGYrHqLElPcUYLfpdEbEC M3J3gH2r7vyZVANoc6QvUY4djO3osD50TYxUmLEE= Message-ID: <6e36e010-c93c-4d9b-a7ed-db6da1416716@dalibo.com> Date: Mon, 18 Aug 2025 18:17:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Safe vm.overcommit_ratio for Large Multi-Instance PostgreSQL Fleet To: Frits Hoogland , Joe Conway Cc: Priya V , pgsql-performance@lists.postgresql.org References: <3A250F65-F5DE-4E24-ADE7-BEFF4A18A8B9@gmail.com> <7fd9f434-e0d9-414b-b396-841ad3c00040@joeconway.com> <1A770E71-8F3C-4D92-816A-44C63AC1AFA7@gmail.com> From: =?UTF-8?Q?Fr=C3=A9d=C3=A9ric_Yhuel?= Content-Language: fr, en-US Autocrypt: addr=frederic.yhuel@dalibo.com; keydata= xjMEXn3bgxYJKwYBBAHaRw8BAQdA6tX5FT/n5ztMWIoBdl6k5avvu65fv6ryfVzIx/aH3V3N JEYuIFlodWVsIDxmcmVkZXJpYy55aHVlbEBkYWxpYm8uY29tPsKWBBMWCAA+FiEEi7OTyf6H ePS+C6n11XGWhN8zGNUFAmZDVJ8CGwMFCQtfi90FCwkIBwIGFQoJCAsCBBYCAwECHgECF4AA CgkQ1XGWhN8zGNV65gEA6o+UrebFjn2CIAOYwP3CiiJugiM5TMH9yJyehQua5ZoA/2ChxiVn 8OUaAw/ErxJmQi1mSN0tNZBL/KhkUPBDUDQNzjgEXn3bgxIKKwYBBAGXVQEFAQEHQCuh5cLQ AtEBXHa2Fmtp0kduBu7msM7qO/gaEcdjFUdiAwEIB8J+BBgWCAAmAhsMFiEEi7OTyf6HePS+ C6n11XGWhN8zGNUFAmZDVJ8FCQtfi90ACgkQ1XGWhN8zGNWOOAEArSqePBqfd4Kx4ulACaWO 6fM+XSDfUlBAQXx9rU6DR4MBALwozl9g91tRysim6lKxggvBfp/PvbpTZNrxYLWB2fYP In-Reply-To: <1A770E71-8F3C-4D92-816A-44C63AC1AFA7@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Archived-At: Precedence: bulk On 8/8/25 10:21, Frits Hoogland wrote: > If swappiness is set to 0, but swap is available, some documentation > suggests it will never use anonymous memory, however I found this not to > be true, linux might still choose anonymous memory to reclaim. A bug in RHEL8 meant that swappiness was not taken into account unless cgroupv2 was configured or vm.force_cgroup_v2_swappiness was set to 1. See references [1] and [2]. Could this be the cause of your observation? [1] https://access.redhat.com/solutions/6785021 [2] https://github.com/systemd/systemd/issues/9276