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Re: 8.4 open item: copy performance regression?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Greg Smith <gsmith(at)gregsmith(dot)com>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Alan Li <ali(at)truviso(dot)com>
Subject: Re: 8.4 open item: copy performance regression?
Date: 2009-06-21 15:31:54
Message-ID: 12404.1245598314@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> It would be interesting to see some gprof or oprofile output from that
> test.   I went back and dug up the results that I got when I profiled
> this patch during initial development, and my version of the patch
> applied, the profile looked like this on my system:

Were you testing with a temp table?  The lack of XLogInsert in your
profile is striking.  Stefan's results upthread had it at the top,
and I got more or less the same thing here (didn't keep my numbers
unfortunately).

> Simon had the idea of further improving performance by keeping the
> current buffer locked (this patch just kept it pinned, but not
> locked), but I didn't see an obvious clean design for that.

The potential for deadlock seems sufficient reason not to do that.

			regards, tom lane

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