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

On Tue, May 14, 2013 at 9:43 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> 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.

I have re-based and reformatted the code, and basic testing shows a
reduction in WAL-file creation time of a fairly significant amount.
I ran 'make test' and did additional local testing without issue.
Therefore, I am attaching the patch. I will try to add it to the
commitfest page.

--
Jon