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From: Nikolay Samokhvalov <nik@postgres.ai>
Date: Fri, 9 Jan 2026 14:29:20 -0800
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Subject: Re: Troubleshooting a brief spike in active sessions
To: "Dirschel, Steve-CW" <Steve.Dirschel@bestbuy.com>
Cc: "pgsql-performance@lists.postgresql.org"
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BTW, what are you logging settings for slow queries?
(log_min_duration_statement, auto_explain.log_min_duration)

On Fri, Jan 9, 2026 at 2:27=E2=80=AFPM Nikolay Samokhvalov <nik@postgres.ai=
> wrote:

> On Fri, Jan 9, 2026 at 1:41=E2=80=AFPM Dirschel, Steve-CW <
> Steve.Dirschel@bestbuy.com> wrote:
> >
> > Aurora Postgres version 17.4
> >
> > ...
> >
> > The app sessions will show as wait_event_type and wait_event as null
> which I understand means they are on CPU
> >
> > ...
>
>
> Not necessarily. It also might be an uninstrumented wait event.
>
> Do the spikes of "CPU" AAS (I prefer to call them "CPU*") correspond well
> to the spikes of high usage?
>
> If you have N active sessions marked as CPU in ASH, does it match to the
> CPU load of similar scale?
>
> If the VM has much less than 400 vCPUs and you see overall CPU load far
> from 100%, then we should suspect some missing wait event.
>
> Nik
>

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<div dir=3D"ltr"><div>BTW, what are you logging settings for slow queries?<=
/div><div>(log_min_duration_statement, auto_explain.log_min_duration)</div>=
</div><br><div class=3D"gmail_quote gmail_quote_container"><div dir=3D"ltr"=
 class=3D"gmail_attr">On Fri, Jan 9, 2026 at 2:27=E2=80=AFPM Nikolay Samokh=
valov &lt;<a href=3D"mailto:nik@postgres.ai">nik@postgres.ai</a>&gt; wrote:=
<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8=
ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr=
">On Fri, Jan 9, 2026 at 1:41=E2=80=AFPM Dirschel, Steve-CW &lt;<a href=3D"=
mailto:Steve.Dirschel@bestbuy.com" target=3D"_blank">Steve.Dirschel@bestbuy=
.com</a>&gt; wrote:<br>&gt;<br>&gt; Aurora Postgres version 17.4<br>&gt;<br=
>&gt; ...<br>&gt;<br>&gt; The app sessions will show as wait_event_type and=
 wait_event as null which I understand means they are on CPU<br>&gt;<br>&gt=
; ...<br><br><br>Not necessarily. It also might be an uninstrumented wait e=
vent.<br><br>Do the spikes of &quot;CPU&quot; AAS (I prefer to call them &q=
uot;CPU*&quot;) correspond well to the spikes of high usage?<br><br>If you =
have N active sessions marked as CPU in ASH, does it match to the CPU load =
of similar scale?<br><br>If the VM has much less than 400 vCPUs and you see=
 overall CPU load far from 100%, then we should suspect some missing wait e=
vent.<br><br>Nik</div>
</blockquote></div>

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