Re: hung backends stuck in spinlock heavy endless loop

Merlin Moncure <mmoncure@gmail.com> writes:
> On Tue, Jan 13, 2015 at 5:54 PM, Peter Geoghegan <pg@heroku.com> wrote:
>> In case it isn't clear, I think that the proximate cause here may well
>> be either one (or both) of commits
>> efada2b8e920adfdf7418862e939925d2acd1b89 and/or
>> 40dae7ec537c5619fc93ad602c62f37be786d161. Probably the latter. I think
>> that the profile is roughly consistent with that, although I may well
>> be wrong.

> I'm out of time for the day, but I'm fairly confident I can reproduce.
> I'll see if I can reverse those commits tomorrow and retest (I'm on
> development box).

I'm not convinced that Peter is barking up the right tree.  I'm noticing
that the profiles seem rather skewed towards parser/planner work; so I
suspect the contention is probably on access to system catalogs.  No
idea exactly why though.

It would be good to collect a few stack traces from the hung backends,
rather than relying on perf statistics.
        regards, tom lane