Re: BUG #14714: long running sessions from remote instance seems to hang some times

If there are no queries on database I see number of context switches from
~900 to ~1500.

I checked our monitoring based on node_exporter, Prometheus and Grafana and
when this "drowsiness" of sessions happens I see number of context switches
from ~10 000 to ~25 000 with a few peeks ~28 000.

But similar numbers or even slightly higher I see also in other cases of
high load on the database and they did not caused any "drowsy" sessions. In
fact monitoring does not show any significant differences between cases
with "drowsy" sessions and without them...If you have some advices about
what else to monitor I will add.

On 23 June 2017 at 16:14, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Josef Machytka <josef(dot)machytka(at)gmail(dot)com> writes:
> > sorry, here is file with sample - basically several group by aggregations
> > over different partitioned tables have been locked in this "drowsy" state
>
> The amount of time being spent in the kernel is strikingly high. I wonder
> if you're seeing some variant of the old "context swap storm" problem.
> Try watching the output of "vmstat 1" for awhile to see if the cs rate
> is high.
>
> regards, tom lane
>