Received: from maia.hub.org (unknown [200.46.204.183])
	by mail.postgresql.org (Postfix) with ESMTP id D8F79632DBC;
	Sat,  6 Feb 2010 08:04:19 -0400 (AST)
Received: from mail.postgresql.org ([200.46.204.86])
	by maia.hub.org (mx1.hub.org [200.46.204.183]) (amavisd-maia,
	port 10024)
	with ESMTP id 71736-04; Sat,  6 Feb 2010 12:04:09 +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 5A9E0632B43;
	Sat,  6 Feb 2010 08:04:09 -0400 (AST)
Received: from alap2.localnet (e178227112.adsl.alicedsl.de [85.178.227.112])
	by mail.anarazel.de (Postfix) with ESMTPSA id 30404448007;
	Sat,  6 Feb 2010 13:04:05 +0100 (CET)
From: Andres Freund <andres@anarazel.de>
To: Greg Smith <greg@2ndquadrant.com>
Subject: Re: [HACKERS] Re: Faster CREATE DATABASE by delaying fsync (was 8.4.1
	ubuntu karmic slow createdb)
Date: Sat, 6 Feb 2010 13:03:50 +0100
User-Agent: KMail/1.13.0 (Linux/2.6.33-rc5-andres-00243-g6ea299e; KDE/4.3.95;
	x86_64; ; )
Cc: Robert Haas <robertmhaas@gmail.com>, Greg Stark <gsstark@mit.edu>,
	Tom Lane <tgl@sss.pgh.pa.us>, 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>
	<4B698605.50506@anarazel.de> <4B6CF822.9010608@2ndquadrant.com>
In-Reply-To: <4B6CF822.9010608@2ndquadrant.com>
MIME-Version: 1.0
Content-Type: Text/Plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Message-Id: <201002061304.01682.andres@anarazel.de>
X-Virus-Scanned: Maia Mailguard 1.0.1
X-Spam-Status: No, hits=-2.599 tagged_above=-10 required=5
	tests=BAYES_00=-2.599
X-Spam-Level: 
X-Archive-Number: 201002/107
X-Sequence-Number: 37528

On Saturday 06 February 2010 06:03:30 Greg Smith wrote:
> Andres Freund wrote:
> > On 02/03/10 14:42, Robert Haas wrote:
> >> Well, maybe we should start with a discussion of what kernel calls
> >> you're aware of on different platforms and then we could try to put an
> >> API around it.
> > 
> > In linux there is sync_file_range. On newer Posixish systems one can
> > emulate that with mmap() and msync() (in batches obviously).
> > 
> > No idea about windows.
> The effective_io_concurrency feature had proof of concept test programs
> that worked using AIO, but actually following through on that
> implementation would require a major restructuring of how the database
> interacts with the OS in terms of reads and writes of blocks.  It looks
> to me like doing something similar to sync_file_range on Windows would
> be similarly difficult.
Looking a bit arround it seems one could achieve something approximediately 
similar to pg_prepare_fsync() by using
CreateFileMapping && MapViewOfFile && FlushViewOfFile 

If I understand it correctly that will flush, but not wait. Unfortunately you 
cant event make it wait, so its not possible to implement sync_file_range or 
similar fully.

Andres