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From: Andrew Dunstan <andrew@dunslane.net>
To: David Fetter <david@fetter.org>
Cc: 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: Mon, 23 Jul 2012 08:29:16 -0400
Message-ID: <500D439C.50608@dunslane.net> (raw)
In-Reply-To: <20120723043733.GA13020@fetter.org>
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	<20120723043733.GA13020@fetter.org>


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



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