Re: fallocate / posix_fallocate for new WAL file creation (etc...)

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Jon Nelson <jnelson+pgsql(at)jamponi(dot)net>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Jim Nasby <jim(at)nasby(dot)net>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Amit Kapila <amit(dot)kapila(at)huawei(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jeff Davis <pgsql(at)j-davis(dot)com>, Florian Pflug <fgp(at)phlo(dot)org>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: fallocate / posix_fallocate for new WAL file creation (etc...)
Date: 2013-05-15 02:43:06
Message-ID: CA+TgmoZUH69T-uDLE7zUfKcP=sUe07zfj8prMWtsGES9h1XTzg@mail.gmail.com
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On Mon, May 13, 2013 at 9:54 PM, Jon Nelson <jnelson+pgsql(at)jamponi(dot)net> wrote:
> Pertinent to another thread titled
> [HACKERS] corrupt pages detected by enabling checksums
> I hope to explore the possibility of using fallocate (or
> posix_fallocate) for new WAL file creation.
>
> Most modern Linux filesystems support fast fallocate/posix_fallocate,
> reducing extent fragmentation (where extents are used) and frequently
> offering a pretty significant speed improvement. In my tests, using
> posix_fallocate (followed by pg_fsync) is at least 28 times quicker
> than using the current method (which writes zeroes followed by
> pg_fsync).
>
> I have written up a patch to use posix_fallocate in new WAL file
> creation, including configuration by way of a GUC variable, but I've
> not contributed to the PostgreSQL project before. Therefore, I'm
> fairly certain the patch is not formatted properly or conforms to the
> appropriate style guides. Currently, the patch is based on 9.2, and is
> quite small in size - 3.6KiB.
>
> Advice on how to proceed is appreciated.

Make sure to list it here:

https://commitfest.postgresql.org/action/commitfest_view/open

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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