Re: Waiting on ExclusiveLock on extension

From: Andomar <andomar(at)aule(dot)net>
To: Qingqing Zhou <zhouqq(dot)postgres(at)gmail(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Waiting on ExclusiveLock on extension
Date: 2015-04-17 08:01:05
Message-ID: 5530BDC1.1050205@aule.net
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> Are you able to take some 'perf top' during high CPU spike and see
> what's burning CPU there? Though the issue is related to blocking, but
> high CPU spikes may hint some spinning to acquire behavior.

Will do, although hopefully the spikes were only growing pains after the
upgrade.

> If your previous relation size is smaller than after upgrade, that's a
> signal that you do have holes in relation, thus extension can be
> avoided sometimes for new tuples.

The relation between high CPU and page splits is not immediately obvious
to me.

We run with synchronous_commit off, but there does seem to be a peak in
I/O requests around the CPU spikes.

Is a page split by nature a synchronous I/O activity? And do the other
connections wait in some kind of CPU intensive form (like a spinlock?)

Kind regards,
Andomar

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