| From: | Dimitrios Apostolou <jimis(at)gmx(dot)net> |
|---|---|
| To: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
| Cc: | Tomas Vondra <tomas(at)vondra(dot)me>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Andres Freund <andres(at)anarazel(dot)de>, Melanie Plageman <melanieplageman(at)gmail(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com> |
| Subject: | Re: [PING] fallocate() causes btrfs to never compress postgresql files |
| Date: | 2025-06-12 12:41:18 |
| Message-ID: | 4e46b377-cae1-09a8-49fa-634cfeb8bd20@gmx.net |
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| Lists: | pgsql-hackers |
On Mon, 9 Jun 2025, Thomas Munro wrote:
> On Tue, Jun 3, 2025 at 1:58 AM Dimitrios Apostolou <jimis(at)gmx(dot)net> wrote:
>> This sounds like the best solution IMO. People can then experiment with
>> different settings and filesystems, and that way we also learn in the
>> process. Thank you for the effort and patches so far.
>
> OK, here's a basic patch to experiment with. You can set:
>
> file_extend_method = fallocate,ftruncate,write
> file_extend_method_threshold = 8 # (below 8 always write, 0 means never write)
>
I applied the patch on PostgreSQL v17 and am testing it now. I chose
ftruncate method and I see ftruncate in action using strace while doing
pg_restore of a big database. Nothing unexpected has happened so far. I
also verified that files are being compressed, obeying Btrfs's mount
option compress=zstd.
Thanks for the patch! What are the odds of commiting it to v17?
Dimitris
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