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From: David Fetter <david@fetter.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Jeff Janes <jeff.janes@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Cc: Daniel Farina <daniel@heroku.com>
Cc: Craig Ringer <ringerc@ringerc.id.au>
Cc: Harold A. Giménez <harold.gimenez@gmail.com>
Subject: Re: Checkpointer split has broken things dramatically (was Re: DELETE vs TRUNCATE explanation)
Date: Sun, 22 Jul 2012 21:37:33 -0700
Message-ID: <20120723043733.GA13020@fetter.org> (raw)
In-Reply-To: <9247.1342565810@sss.pgh.pa.us>
References: <CA+TgmoaTf=zjP37-oG7fr1VbGfuvHSfpajgLZ65EeSJX2mmquA@mail.gmail.com>
	<9603.1342454919@sss.pgh.pa.us>
	<CA+Tgmoa4ta60Y-rZpEPDRCQKJV8-Uqe0P610Jgj2q7e+fondig@mail.gmail.com>
	<11952.1342456591@sss.pgh.pa.us>
	<CA+TgmoYRXMWQ_DGmmqu3Zp8oW3Lt-9Lc1q3EHaV_ZmjWqaPkuA@mail.gmail.com>
	<13011.1342457859@sss.pgh.pa.us>
	<CA+TgmoaEPLo5fmBX1JSkGK3umAamFVghwY7qDb4_QqzteZgUPA@mail.gmail.com>
	<15955.1342466333@sss.pgh.pa.us>
	<CA+TgmoYnqP!f03rYJo3G6dMrqShQF2iMtfpYBPgWdxtEdacaX-w@mail.gmail.com>
	<9247.1342565810@sss.pgh.pa.us>

On Tue, Jul 17, 2012 at 06:56:50PM -0400, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > On Mon, Jul 16, 2012 at 3:18 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >> BTW, while we are on the subject: hasn't this split completely
> >> broken the statistics about backend-initiated writes?
> 
> > Yes, it seems to have done just that.
> 
> This implies that nobody has done pull-the-plug testing on either
> HEAD or 9.2 since the checkpointer split went in (2011-11-01),
> because even a modicum of such testing would surely have shown that
> we're failing to fsync a significant fraction of our write traffic.
> 
> Furthermore, I would say that any performance testing done since
> then, if it wasn't looking at purely read-only scenarios, isn't
> worth the electrons it's written on.  In particular, any performance
> gain that anybody might have attributed to the checkpointer splitup
> is very probably hogwash.
> 
> This is not giving me a warm feeling about our testing practices.

Is there any part of this that the buildfarm, or some other automation
framework, might be able to handle?

Cheers,
David.
-- 
David Fetter <david@fetter.org> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david.fetter@gmail.com
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