Received: from maia.hub.org (unknown [200.46.208.211])
	by mail.postgresql.org (Postfix) with ESMTP id 864EE63540D;
	Tue,  2 Feb 2010 14:55:23 -0400 (AST)
Received: from mail.postgresql.org ([200.46.204.86])
	by maia.hub.org (mx1.hub.org [200.46.208.211]) (amavisd-maia,
	port 10024)
	with ESMTP id 61191-09-2; Tue,  2 Feb 2010 18:55:01 +0000 (UTC)
X-Greylist: from auto-whitelisted by SQLgrey-1.7.6
X-Greylist: from auto-whitelisted by SQLgrey-1.7.6
Received: from mail.anarazel.de (mail.anarazel.de [217.115.131.40])
	by mail.postgresql.org (Postfix) with ESMTP id 5B56E636F2A;
	Tue,  2 Feb 2010 14:34:21 -0400 (AST)
Received: from alap2.localnet (p579FAFE6.dip.t-dialin.net [87.159.175.230])
	by mail.anarazel.de (Postfix) with ESMTPSA id 8CCDD448005;
	Tue,  2 Feb 2010 19:34:19 +0100 (CET)
From: Andres Freund <andres@anarazel.de>
To: Robert Haas <robertmhaas@gmail.com>
Subject: Re: [HACKERS] Re: Faster CREATE DATABASE by delaying fsync (was 8.4.1
	ubuntu karmic slow createdb)
Date: Tue, 2 Feb 2010 19:34:07 +0100
User-Agent: KMail/1.13.0 (Linux/2.6.33-rc5-andres-00243-g6ea299e; KDE/4.3.95;
	x86_64; ; )
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Greg Stark <gsstark@mit.edu>,
	pgsql-hackers@postgresql.org, pgsql-performance@postgresql.org,
	Michael Clemmons <glassresistor@gmail.com>,
	Hannu Krosing <hannu@2ndquadrant.com>,
	Scott Marlowe <scott.marlowe@gmail.com>
References: <4427a97a0912101235x3ade510blcc00d5ce9883c6b6@mail.gmail.com>
	<23321.1265133015@sss.pgh.pa.us>
	<603c8f071002021014h4b489f44s9014377e1b38dbc7@mail.gmail.com>
In-Reply-To: <603c8f071002021014h4b489f44s9014377e1b38dbc7@mail.gmail.com>
MIME-Version: 1.0
Content-Type: Text/Plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Message-Id: <201002021934.18444.andres@anarazel.de>
X-Virus-Scanned: Maia Mailguard 1.0.1
X-Spam-Status: No, hits=-2.421 tagged_above=-10 required=5 tests=AWL=0.178,
	BAYES_00=-2.599
X-Spam-Level: 
X-Archive-Number: 201002/20
X-Sequence-Number: 37441

On Tuesday 02 February 2010 19:14:40 Robert Haas wrote:
> On Tue, Feb 2, 2010 at 12:50 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > Andres Freund <andres@anarazel.de> writes:
> >> On Tuesday 02 February 2010 18:36:12 Robert Haas wrote:
> >>> I took a look at this patch today and I agree with Tom that
> >>> pg_fsync_start() is a very confusing name.  I don't know what the
> >>> right name is, but this doesn't fsync so I don't think it shuld have
> >>> fsync in the name.  Maybe something like pg_advise_abandon() or
> >>> pg_abandon_cache().  The current name is really wishful thinking:
> >>> you're hoping that it will make the kernel start the fsync, but it
> >>> might not.  I think pg_start_data_flush() is similarly optimistic.
> >> 
> >> What about: pg_fsync_prepare().
> > 
> > prepare_for_fsync()?
> 
> It still seems mis-descriptive to me.  Couldn't the same routine be
> used simply to abandon undirtied data that we no longer care about
> caching?
For now it could - but it very well might be converted to sync_file_range or 
similar, which would have different "sideeffects".

As the potential code duplication is rather small I would prefer to describe 
the prime effect not the sideeffects...

Andres