Horton

Re: Direct I/O

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Andrew Dunstan <andrew@dunslane.net>, Andres Freund <andres@anarazel.de>, Heikki Linnakangas <hlinnaka@iki.fi>, Noah Misch <noah@leadboat.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Justin Pryzby <pryzby@telsasoft.com>, pgsql-hackers@postgresql.org
Date: 2023-04-08T23:05:22Z
Lists: pgsql-hackers 
Thomas Munro <thomas.munro@gmail.com> writes:
> On Sun, Apr 9, 2023 at 10:08 AM Andrew Dunstan <andrew@dunslane.net> wrote:
>> btrfs

> Aha!

Googling finds a lot of suggestions that O_DIRECT doesn't play nice
with btrfs, for example

https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg92824.html

It's not clear to me how much of that lore is still current,
but it's disturbing.

			regards, tom lane

Commits

  1. Rename hook functions for debug_io_direct to match variable name.

  2. Rename io_direct to debug_io_direct.

  3. Skip the 004_io_direct.pl test if a pre-flight check fails.

  4. Use higher wal_level for 004_io_direct.pl.

  5. Skip \password TAP test on old IPC::Run versions

  6. Add io_direct setting (developer-only).

  7. Introduce PG_IO_ALIGN_SIZE and align all I/O buffers.

  8. Add palloc_aligned() to allow aligned memory allocations

  9. initdb: When running CREATE DATABASE, use STRATEGY = WAL_COPY.