Horton

Re: Direct I/O

Andrew Dunstan <andrew@dunslane.net>

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From: Andrew Dunstan <andrew@dunslane.net>
To: Thomas Munro <thomas.munro@gmail.com>, Christoph Berg <myon@debian.org>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2023-04-12T13:08:42Z
Lists: pgsql-hackers 
On 2023-04-12 We 01:48, Thomas Munro wrote:
> On Wed, Apr 12, 2023 at 3:04 PM Thomas Munro<thomas.munro@gmail.com>  wrote:
>> On Wed, Apr 12, 2023 at 2:56 PM Christoph Berg<myon@debian.org>  wrote:
>>> I'm hitting a panic in t_004_io_direct. The build is running on
>>> overlayfs on tmpfs/ext4 (upper/lower) which is probably a weird
>>> combination but has worked well for building everything over the last
>>> decade. On Debian unstable:
>>>
>>> PANIC:  could not open file "pg_wal/000000010000000000000001": Invalid argument
>> ... I have a new idea:  perhaps it is possible to try
>> to open a file with O_DIRECT from perl, and if it fails like that,
>> skip the test.  Looking into that now.
> I think I have that working OK.  Any Perl hackers want to comment on
> my use of IO::File (copied from examples on the internet that showed
> how to use O_DIRECT)?  I am not much of a perl hacker but according to
> my package manager, IO/File.pm came with perl itself.  And the Fcntl
> eval trick that I copied from File::stat, and the perl-critic
> suppression that requires?


I think you can probably replace a lot of the magic here by simply saying


if (Fcntl->can("O_DIRECT")) ...


cheers


andrew

--
Andrew Dunstan
EDB:https://www.enterprisedb.com

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.