On Sun, Aug 7, 2016 at 5:33 PM, Ilya Kosmodemiansky
<ilya.kosmodemian...@postgresql-consulting.com> wrote:
> Hi,
> I've summarized Wait events monitoring discussion at Developer unconference
> in Ottawa this year on wiki:
> https://wiki.postgresql.org/wiki/PgCon_2016_Developer_Unconference/Wait_events_monitoring
> (Thanks to Alexander Korotkov for patiently pushing me to make this thing
> finally done)
> If you attended, fill free to point me out if I missed something, I will put
> it on the wiki too.

Thanks for summarization.

> Wait event monitoring looks ones again stuck on the way through community
> approval in spite of huge progress done last year in that direction. The
> importance of the topic is beyond discussion now, if you talk to any
> PostgreSQL person about implementing such a tool in Postgres and if the
> person does not get exited, probably you talk to a full-time PostgreSQL
> developer;-) Obviously it needs a better design, both the user interface and
> implementation, and perhaps this is why full-time developers are still
> sceptical.
> In order to move forward, imho we need at least some steps, whose steps can
> be done in parallel
> 1. Further requirements need to be collected from DBAs.
>    If you are a PostgreSQL DBA with Oracle experience and use perf for
> troubleshooting Postgres - you are an ideal person to share your experience,
> but everyone is welcome.
> 2. Further pg_wait_sampling performance testing needed and in different
> environments.

I think it is better to first go with a knob whose default value will
be off.  We can do the performance testing as well and if by end of
release nobody reported any visible regression, then we can discuss
for changing the default to on.

>    According to developers, overhead is small, but many people have doubts
> that it can be much more significant for intensive workloads. Obviously, it
> is not an easy task to test, because you need to put doubtfully
> non-production ready code into mission-critical production for such tests.
>    As a result it will be clear if this design should be abandoned  and we
> need to think about less-invasive solutions or this design is acceptable.

I think here main objection was that gettimeofday can cause
performance regression which can be taken care by using configurable
knob.  I am not aware if any other part of the design has been
discussed in detail to conclude whether it has any obvious problem.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

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