Message-ID: <500D439C.50608@dunslane.net>
Date: Mon, 23 Jul 2012 08:29:16 -0400
From: Andrew Dunstan <andrew@dunslane.net>
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To: David Fetter <david@fetter.org>
CC: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>,
	Jeff Janes <jeff.janes@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>,
	Daniel Farina <daniel@heroku.com>,
	Craig Ringer <ringerc@ringerc.id.au>, =?ISO-8859-1?Q?=22Harold_A=2E_?=
	=?ISO-8859-1?Q?Gim=E9nez=22?= <harold.gimenez@gmail.com>
Subject: Re: Checkpointer split has broken things dramatically (was
	Re: DELETE vs TRUNCATE explanation)
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> <20120723043733.GA13020@fetter.org>
In-Reply-To: <20120723043733.GA13020@fetter.org>
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On 07/23/2012 12:37 AM, David Fetter wrote:
> 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?
>

I'm not sure how you automate testing a pull-the-plug scenario.

The buildfarm is not at all designed to test performance. That's why we 
want a performance farm.

cheers

andrew