Received: from localhost (unknown [200.46.204.183])
	by postgresql.org (Postfix) with ESMTP id 418502E0030
	for <pgsql-hackers-postgresql.org@postgresql.org>;
	Fri, 28 Mar 2008 15:49:24 -0300 (ADT)
Received: from postgresql.org ([200.46.204.71])
	by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024)
	with ESMTP id 61099-10 for
	<pgsql-hackers-postgresql.org@postgresql.org>;
	Fri, 28 Mar 2008 15:49:15 -0300 (ADT)
X-Greylist: from auto-whitelisted by SQLgrey-1.7.5
Received: from svana.org (svana.org [203.190.233.187])
	by postgresql.org (Postfix) with ESMTP id 607222E004F
	for <pgsql-hackers@postgresql.org>;
	Fri, 28 Mar 2008 15:49:15 -0300 (ADT)
Received: from kleptog by svana.org with local (Exim 4.50)
	id 1JfJd9-0005oY-Fd; Sat, 29 Mar 2008 05:48:47 +1100
Date: Fri, 28 Mar 2008 19:48:47 +0100
From: Martijn van Oosterhout <kleptog@svana.org>
To: Gregory Stark <stark@enterprisedb.com>
Cc: Bruce Momjian <bruce@momjian.us>,
 Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Commitfest patches
Message-ID: <20080328184847.GE9150@svana.org>
Reply-To: Martijn van Oosterhout <kleptog@svana.org>
References: <200803281545.m2SFjpL18390@momjian.us>
	<87r6duycpl.fsf@oxford.xeocode.com>
Mime-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha1;
	protocol="application/pgp-signature"; boundary="x4pBfXISqBoDm8sr"
Content-Disposition: inline
In-Reply-To: <87r6duycpl.fsf@oxford.xeocode.com>
X-PGP-Key-ID: Length=1024; ID=0x6F0B424C
X-PGP-Key-Fingerprint: 34A8 8EAC F902 8C8D CA72  DCC7 201E DB34 6F0B 424C
User-Agent: Mutt/1.5.9i
X-SA-Exim-Connect-IP: <locally generated>
X-SA-Exim-Mail-From: kleptog@svana.org
X-SA-Exim-Scanned: No (on svana.org); SAEximRunCond expanded to false
X-Virus-Scanned: Maia Mailguard 1.0.1
X-Archive-Number: 200803/1200
X-Sequence-Number: 116001


--x4pBfXISqBoDm8sr
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Fri, Mar 28, 2008 at 05:34:30PM +0000, Gregory Stark wrote:
> But what I really need is someone to read the patch and say "looks good" =
or
> point out things they don't like. In particular, what I really, really wa=
nt is
> some guidance on the singular key question I asked.

I was going to write all sorts of stuff, till I noticed Heikki said
basically everything I was going to say:

- I think normal index scans could benefit from this (it was measurable
when I was playing with AIO in postgres a few years back).
- The integration with the bitmap scan is good, neat even
- I think the number of preread_count is far too small, given you get a
benefit even if you only have one spindle.
- I don't understand the ramp-up method either.

People spend a lot of time worrying about hundreds of posix_fadvise()
calls but you don't need anywhere near that much to be effective. With
AIO I limited the number of outstanding requests to a dozen and it was
still useful. You lose nothing by capping the number of requests at any
point.

> I want to know if we're interested in the more invasive patch restructuri=
ng
> the buffer manager. My feeling is that we probably are eventually. But I
> wonder if people wouldn't feel more comfortable taking baby steps at first
> which will have less impact in cases where it's not being heavily used.

I think the way it is now is neat and simple and enough for now.

Have a nice day,
--=20
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> Please line up in a tree and maintain the heap invariant while=20
> boarding. Thank you for flying nlogn airlines.

--x4pBfXISqBoDm8sr
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: Digital signature
Content-Disposition: inline

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.1 (GNU/Linux)

iD8DBQFH7T2PIB7bNG8LQkwRAmYLAJ9pTRg8eOIJQJnxMuzHg/KuK9BlgwCeJh9t
6sO/3yPgEu/L0v+Jxwbe/Q8=
=aBBA
-----END PGP SIGNATURE-----

--x4pBfXISqBoDm8sr--