Date: Fri, 22 Aug 2025 17:19:33 +0200
From: hubert depesz lubaczewski <depesz@depesz.com>
Sender: depesz@depesz.com
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Adrian Klaver <adrian.klaver@aklaver.com>,
	PostgreSQL General <pgsql-general@lists.postgresql.org>,
	Chris Wilson <chris+google@qwirx.com>
Subject: Re: Streaming replica hangs periodically for ~ 1 second - how to
 diagnose/debug
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On Fri, Aug 22, 2025 at 05:07:09PM +0200, Pavel Stehule wrote:
> > Any idea on what could it be?
> Few years ago I had a similar experience - some sec mystic lags - the
> problem was in virtualization.

While I can't discount this idea, after all it is aws ec2, so virtual
boxes, what makes me wonder is:

in case of this slow situation there is futex call, which takes
a second. But there are no futex calls in any other query processing
logs.

So, while it is obvious that futex "wasted" this time, the question is:
why would pg run futex() for this one query at all?

Best regards,

depesz