Re: Direct I/O

On 2023-04-12 We 01:48, Thomas Munro wrote:
> On Wed, Apr 12, 2023 at 3:04 PM Thomas Munro<thomas(dot)munro(at)gmail(dot)com> wrote:
>> On Wed, Apr 12, 2023 at 2:56 PM Christoph Berg<myon(at)debian(dot)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