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From: Andres Freund <andres@anarazel.de>
To: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Re: Faster CREATE DATABASE by delaying fsync (was 8.4.1
	ubuntu karmic slow createdb)
Date: Tue, 19 Jan 2010 16:03:16 +0100
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Cc: Greg Stark <gsstark@mit.edu>, pgsql-performance@postgresql.org,
	Michael Clemmons <glassresistor@gmail.com>,
	Hannu Krosing <hannu@2ndquadrant.com>,
	Scott Marlowe <scott.marlowe@gmail.com>
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On Tuesday 19 January 2010 15:52:25 Greg Stark wrote:
> On Mon, Jan 18, 2010 at 4:35 PM, Greg Stark <gsstark@mit.edu> wrote:
> > Looking at this patch for the commitfest I have a few questions.
> 
> So I've touched this patch up a bit:
> 
> 1) moved the posix_fadvise call to a new fd.c function
> pg_fsync_start(fd,offset,nbytes) which initiates an fsync without
> waiting on it. Currently it's only implemented with
> posix_fadvise(DONT_NEED) but I want to look into using sync_file_range
> in the future -- it looks like this call might be good enough for our
> checkpoints.
> 
> 2) advised each 64k chunk as we write it which should avoid poisoning
> the cache if you do a large create database on an active system.
> 
> 3) added the promised but afaict missing fsync of the directory -- i
> think we should actually backpatch this.
Yes, that was a bit stupid from me - I added the fsync for directories which 
get recursed into (by not checking if its a file) but not for the uppermost 
level.
So all directories should get fsynced right now but the topmost one.

I will review the patch later when I finally will have some time off again... 
~4h.

Thanks!

Andres