From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
---|---|
To: | Peter Geoghegan <pg(at)heroku(dot)com> |
Cc: | Merlin Moncure <mmoncure(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: hung backends stuck in spinlock heavy endless loop |
Date: | 2015-01-13 23:54:04 |
Message-ID: | 20150113235404.GB22986@alap3.anarazel.de |
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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(at)2ndquadrant(dot)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
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