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

On Mon, May 13, 2013 at 08:54:39PM -0500, Jon Nelson 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.

Thanks for hopping in!

Please re-base the patch vs. git master, as new features like this go
there. Please also to send along the tests you're doing so others can
riff. Tests that find any weak points are also good.

Cheers,
David.
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