Re: Direct I/O

Andrew Dunstan <andrew@dunslane.net>

From: Andrew Dunstan <andrew@dunslane.net>
To: Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>
Cc: Thomas Munro <thomas.munro@gmail.com>, 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: 2023-04-08T22:08:41Z
Lists: pgsql-hackers
On 2023-04-08 Sa 17:42, Andres Freund wrote:
> Hi,
>
> On 2023-04-08 17:31:02 -0400, Tom Lane wrote:
>> Andres Freund<andres@anarazel.de>  writes:
>>> On 2023-04-08 17:10:19 -0400, Tom Lane wrote:
>>> It's also odd that it's just crake having the issue. It's just a linux host,
>>> afaics.
>> Indeed.  I'm guessing from the compiler version that it's Fedora 37 now
> The 15 branch says:
>
> hostname = neoemma
> uname -m = x86_64
> uname -r = 6.2.8-100.fc36.x86_64
> uname -s = Linux
> uname -v = #1 SMP PREEMPT_DYNAMIC Wed Mar 22 19:14:19 UTC 2023
>
> So at least the kernel claims to be 36...
>
>
>> (the lack of such basic information in the meson configuration output
>> is pretty annoying).
> Yea, I was thinking yesterday that we should add uname output to meson's
> configure (if available). I'm sure we can figure out a reasonably fast windows
> command for the version, too.
>
>
>> I've been trying to repro it here on an F37 box, with no success, suggesting
>> that it's very timing sensitive.  Or maybe it's inside a VM and that
>> matters?
> Could also be filesystem specific?
>

I migrated it in February from a VM to a non-virtual instance. Almost 
nothing else runs on the machine. The personality info shown on the BF 
server is correct.

andrew@neoemma:~ $ cat /etc/fedora-release
Fedora release 36 (Thirty Six)
andrew@neoemma:~ $ uname -a
Linux neoemma 6.2.8-100.fc36.x86_64 #1 SMP PREEMPT_DYNAMIC Wed Mar 22 
19:14:19 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
andrew@neoemma:~ $ gcc --version
gcc (GCC) 12.2.1 20221121 (Red Hat 12.2.1-4)
andrew@neoemma:~ $ mount | grep home
/dev/mapper/luks-xxxxxxx on /home type btrfs 
(rw,relatime,seclabel,compress=zstd:1,ssd,discard=async,space_cache,subvolid=256,subvol=/home)


I guess it could be btrfs-specific. I'll be somewhat annoyed if I have 
to re-init the machine to use something else.


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.