Re: Wait events monitoring future development

2016/08/10 23:22 "Bruce Momjian" <bruce(at)momjian(dot)us>:
>
> On Wed, Aug 10, 2016 at 05:14:52PM +0300, Alexander Korotkov wrote:
> > On Tue, Aug 9, 2016 at 5:37 AM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> >
> > On Tue, Aug 9, 2016 at 02:06:40AM +0000, Tsunakawa, Takayuki wrote:
> > > I hope wait event monitoring will be on by default even if the
overhead
> > is not
> > > almost zero, because the data needs to be readily available for
faster
> > > troubleshooting. IMO, the benefit would be worth even 10%
overhead. If
> > you
> > > disable it by default because of overhead, how can we convince
users to
> > enable
> > > it in production systems to solve some performance problem? I’m
afraid
> > severe
> > > users would say “we can’t change any setting that might cause more
> > trouble, so
> > > investigate the cause with existing information.”
> >
> > If you want to know why people are against enabling this monitoring
by
> > default, above is the reason. What percentage of people do you
think
> > would be willing to take a 10% performance penalty for monitoring
like
> > this? I would bet very few, but the argument above doesn't seem to
> > address the fact it is a small percentage.
> >
> >
> > Just two notes from me:
> >
> > 1) 10% overhead from monitoring wait events is just an idea without any
proof
> > so soon.
> > 2) We already have functionality which trades insight into database
with way
> > more huge overhead. auto_explain.log_analyze = true can slowdown
queries *in
> > times*. Do you think we should remove it?
>
> The point is not removing it, the point is whether
> auto_explain.log_analyze = true should be enabled by default, and I
> think no one wants to do that.

Agreed.

If people are facing with some difficult situation in terms of performance,
they may accept some (one-time) overhead to resolve the issue.
But if they don't have (recognize) any issue, they may not.

That's one of the realities according to my experiences.

Regards,