Re: hung backends stuck in spinlock heavy endless loop

On 2015-01-13 17:39:09 -0600, Merlin Moncure wrote:
> On Tue, Jan 13, 2015 at 5:21 PM, Andres Freund <andres@2ndquadrant.com> wrote:
> > On 2015-01-13 15:17:15 -0800, Peter Geoghegan wrote:
> >> I'm inclined to think that this is a livelock, and so the problem
> >> isn't evident from the structure of the B-Tree, but it can't hurt to
> >> check.
> >
> > My guess is rather that it's contention on the freelist lock via
> > StrategyGetBuffer's. I've seen profiles like this due to exactly that
> > before - and it fits to parallel loading quite well.
> 
> I think I've got it to pop again. s_lock is only showing 35%
> (increasing very slowly if at all) but performance is mostly halted.
> Frame pointer is compiled out.  perf report attached.

>  35.82%  postgres                            [.] s_lock
>  23.71%  postgres                            [.] tas
>  14.01%  postgres                            [.] tas
>   6.82%  postgres                            [.] spin_delay
>   5.93%  postgres                            [.] LWLockRelease
>   4.36%  postgres                            [.] LWLockAcquireCommon

Interesting. This profile looks quite different?

What kind of hardware is this on?

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services