Date: Thu, 21 Jul 2022 14:33:27 -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: <20220721193327.GP12702@telsasoft.com>
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On Thu, Jul 21, 2022 at 02:37:35PM -0400, bruno da silva wrote:
> I'm investigating an issue on a PostgresSql 9.5.21 installation that
> becomes unusable in an intermittent way. Simple queries like "select
> now();" could take 20s. commits take 2s. and all gets fixed after an engine
> restart.
> 
> I look into the pg logs and no signs of errors. and checkpoints are
> always timed. The machine is well provisioned, load isn't too high, and cpu
> io wait is under 1%.
> 
> any suggestions on what I should check more?

What OS/version is it ?

What GUCs have you changed ?

Is it a new issue ?

https://wiki.postgresql.org/wiki/Slow_Query_Questions

Operating system+version
What OS / version ? At least for linux, you can get the distribution by running: tail /etc/*release 

GUC Settings
What database configuration settings have you changed? What are their values? (These are things like "shared_buffers", "work_mem", "enable_seq_scan", "effective_io_concurrency", "effective_cache_size", etc). See Server Configuration for a useful query that will show all of your non-default database settings, in an easier to read format than posting pieces of your postgresql.conf file. 

-- 
Justin