Horton

Re: hung backends stuck in spinlock heavy endless loop

Andres Freund <andres@2ndquadrant.com>

View thread View on postgr.es
From: Andres Freund <andres@2ndquadrant.com>
To: Peter Geoghegan <pg@heroku.com>
Cc: Merlin Moncure <mmoncure@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2015-01-13T23:54:04Z
Lists: pgsql-hackers 
On 2015-01-13 15:49:33 -0800, Peter Geoghegan wrote:
> On Tue, Jan 13, 2015 at 3:21 PM, Andres Freund <andres@2ndquadrant.com> wrote:
> > 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'm not saying you're wrong, but the breakdown of _bt_moveright()
> relative to _bt_relandgetbuf() calls seems a bit fishy to me.

The hierarchical profile definitely doesn't look like my guess was
right.

> I don't remember seeing _bt_moveright()  or _bt_compare() figuring so
> prominently, where _bt_binsrch() is nowhere to be seen. I can't see a
> reference to _bt_binsrch() in either profile.

Well, we do a _bt_moveright pretty early on, so that actually might be
cache misses we're primarily seing.

Greetings,

Andres Freund

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

Commits

  1. Improve hash_create's API for selecting simple-binary-key hash functions.

  2. Fix WAL-logging of B-tree "unlink halfdead page" operation.

  3. Fix backup-block numbering in redo of b-tree split.

  4. Cleanup of new b-tree page deletion code.

  5. Fix bug in the new B-tree incomplete-split code.

  6. Fix bug in new B-tree page deletion code.

  7. Fix rm_desc routine of b-tree page delete records.

  8. Make the handling of interrupted B-tree page splits more robust.

  9. Fix race condition in B-tree page deletion.