| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Greg Stark <gsstark(at)mit(dot)edu> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, Greg Smith <greg(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-performance(at)postgresql(dot)org, Michael Clemmons <glassresistor(at)gmail(dot)com>, Hannu Krosing <hannu(at)2ndquadrant(dot)com>, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
| Subject: | Re: [HACKERS] Faster CREATE DATABASE by delaying fsync (was 8.4.1 ubuntu karmic slow createdb) |
| Date: | 2009-12-29 11:13:21 |
| Message-ID: | 200912291213.21721.andres@anarazel.de |
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| Thread: | |
| Lists: | pgsql-hackers pgsql-performance |
On Tuesday 29 December 2009 11:48:10 Greg Stark wrote:
> On Tue, Dec 29, 2009 at 2:05 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > Reads Completed: 2, 8KiB Writes Completed: 2362,
> > 29672KiB New:
> > Reads Completed: 0, 0KiB Writes Completed: 550,
> > 5960KiB
>
> It looks like the new method is only doing 1/6th as much i/o. Do you
> know what's going on there?
While I was surprised by the amount of difference I am not surprised at all
that there is a significant one - currently the fsync will write out a whole
bunch of useless stuff every time its called (all metadata, directory structure
and so on)
This is reproducible...
6MB sounds sensible for the operation btw - the template database is around
5MB.
Will try to analyze later what exactly causes the additional io.
Andres
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