From: Andres Freund <andres@anarazel.de>
To: pgsql-performance@postgresql.org
To: pgsql-hackers@postgresql.org
Cc: Michael Clemmons <glassresistor@gmail.com>
Cc: Hannu Krosing <hannu@2ndquadrant.com>
Cc: Scott Marlowe <scott.marlowe@gmail.com>
Subject: Faster CREATE DATABASE by delaying fsync (was 8.4.1 ubuntu karmic slow createdb)
Date: Mon, 28 Dec 2009 23:54:51 +0100
Message-ID: <200912282354.51892.andres@anarazel.de> (raw)
In-Reply-To: <200912122138.42404.andres@anarazel.de>
References: <4427a97a0912101235x3ade510blcc00d5ce9883c6b6@mail.gmail.com>
<4427a97a0912121236g4c06c562u221d638810ed2b6e@mail.gmail.com>
<200912122138.42404.andres@anarazel.de>
On Saturday 12 December 2009 21:38:41 Andres Freund wrote:
> On Saturday 12 December 2009 21:36:27 Michael Clemmons wrote:
> > If ppl think its worth it I'll create a ticket
> Thanks, no need. I will post a patch tomorrow or so.
Well. It was a long day...
Anyway.
In this patch I delay the fsync done in copy_file and simply do a second pass
over the directory in copy_dir and fsync everything in that pass.
Including the directory - which was not done before and actually might be
necessary in some cases.
I added a posix_fadvise(..., FADV_DONTNEED) to make it more likely that the
copied file reaches storage before the fsync. Without the speed benefits were
quite a bit smaller and essentially random (which seems sensible).
This speeds up CREATE DATABASE from ~9 seconds to something around 0.8s on my
laptop. Still slower than with fsync off (~0.25) but quite a worthy
improvement.
The benefits are obviously bigger if the template database includes anything
added.
Andres
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To: pgsql-hackers@postgresql.org
Cc: andres@anarazel.de, pgsql-performance@postgresql.org, glassresistor@gmail.com, hannu@2ndquadrant.com, scott.marlowe@gmail.com
Subject: Re: Faster CREATE DATABASE by delaying fsync (was 8.4.1 ubuntu karmic slow createdb)
In-Reply-To: <200912282354.51892.andres@anarazel.de>
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