Date: Thu, 21 Jul 2022 15:21:46 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: bruno da silva <brunogiovs@gmail.com>
Cc: pgsql-performance@lists.postgresql.org
Subject: Re: PostgresSQL 9.5.21 very slow to connect and perform basic queries
Message-ID: <20220721202146.GR12702@telsasoft.com>
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On Thu, Jul 21, 2022 at 03:59:30PM -0400, bruno da silva wrote:
>   OS/version: CentOS release 6.9 (Final)

How are these set ?

tail /sys/kernel/mm/ksm/run /sys/kernel/mm/transparent_hugepage/{defrag,enabled,khugepaged/defrag} /proc/sys/vm/zone_reclaim_mode

I suspect you may be suffering from issues with transparent huge pages.

I suggest to disable KSM and THP, or upgrade to a newer OS.

I've written before about these:
https://www.postgresql.org/message-id/20170524155855.GH31097@telsasoft.com
https://www.postgresql.org/message-id/20190625162338.GF18602@telsasoft.com
https://www.postgresql.org/message-id/20170718180152.GE17566@telsasoft.com
https://www.postgresql.org/message-id/20191004060300.GA11241@telsasoft.com
https://www.postgresql.org/message-id/20200413144254.GS2228@telsasoft.com
https://www.postgresql.org/message-id/20220329182453.GA28503@telsasoft.com

On Thu, Jul 21, 2022 at 04:01:10PM -0400, bruno da silva wrote:
> The issue started a month ago.

Ok .. but how long has the DB been running under this environment ?

-- 
Justin