From: Lennart Poettering <lennart@poettering.net>
To: Russell Coker <russell@coker.com.au>
Cc: kreijack@inwind.it, Duncan <1i5t5.duncan@cox.net>,
linux-btrfs@vger.kernel.org, systemd-devel@lists.freedesktop.org
Subject: Re: [systemd-devel] Slow startup of systemd-journal on BTRFS
Date: Mon, 16 Jun 2014 12:14:49 +0200 [thread overview]
Message-ID: <20140616101448.GB18016@tango.0pointer.de> (raw)
In-Reply-To: <1709025.rRUgx5gMp1@xev>
On Mon, 16.06.14 10:17, Russell Coker (russell@coker.com.au) wrote:
> > I am not really following though why this trips up btrfs though. I am
> > not sure I understand why this breaks btrfs COW behaviour. I mean,
> > fallocate() isn't necessarily supposed to write anything really, it's
> > mostly about allocating disk space in advance. I would claim that
> > journald's usage of it is very much within the entire reason why it
> > exists...
>
> I don't believe that fallocate() makes any difference to fragmentation on
> BTRFS. Blocks will be allocated when writes occur so regardless of an
> fallocate() call the usage pattern in systemd-journald will cause
> fragmentation.
journald's write pattern looks something like this: append something to
the end, make sure it is written, then update a few offsets stored at
the beginning of the file to point to the newly appended data. This is
of course not easy to handle for COW file systems. But then again, it's
probably not too different from access patterns of other database or
database-like engines...
Lennart
--
Lennart Poettering, Red Hat
next prev parent reply other threads:[~2014-06-16 10:14 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-12 11:13 R: Re: Slow startup of systemd-journal on BTRFS Goffredo Baroncelli <kreijack@libero.it>
2014-06-12 12:37 ` Duncan
2014-06-12 23:24 ` Dave Chinner
2014-06-13 22:19 ` Goffredo Baroncelli
2014-06-14 2:53 ` Duncan
2014-06-14 7:52 ` Goffredo Baroncelli
2014-06-15 5:43 ` Duncan
2014-06-15 22:39 ` [systemd-devel] " Lennart Poettering
2014-06-15 22:13 ` Lennart Poettering
2014-06-16 0:17 ` Russell Coker
2014-06-16 1:06 ` John Williams
2014-06-16 2:19 ` Russell Coker
2014-06-16 10:14 ` Lennart Poettering [this message]
2014-06-16 10:35 ` Russell Coker
2014-06-16 11:16 ` Austin S Hemmelgarn
2014-06-16 11:56 ` Andrey Borzenkov
2014-06-16 16:05 ` Josef Bacik
2014-06-16 19:52 ` Martin
2014-06-16 20:20 ` Josef Bacik
2014-06-17 0:15 ` Austin S Hemmelgarn
2014-06-17 1:13 ` cwillu
2014-06-17 12:24 ` Martin
2014-06-17 17:56 ` Chris Murphy
2014-06-17 18:46 ` Filipe Brandenburger
2014-06-17 19:42 ` Goffredo Baroncelli
2014-06-17 21:12 ` Lennart Poettering
2014-06-16 16:32 ` Goffredo Baroncelli
2014-06-16 18:47 ` Goffredo Baroncelli
2014-06-19 1:13 ` Dave Chinner
2014-06-14 10:59 ` Kai Krakow
2014-06-15 5:02 ` Duncan
2014-06-15 11:18 ` Kai Krakow
2014-06-15 21:45 ` Martin Steigerwald
2014-06-15 21:51 ` Hugo Mills
2014-06-15 22:43 ` [systemd-devel] " Lennart Poettering
2014-06-15 21:31 ` Martin Steigerwald
2014-06-15 21:37 ` Hugo Mills
2014-06-17 8:22 ` Duncan
-- strict thread matches above, loose matches on Subject: below --
2014-06-11 21:28 Goffredo Baroncelli
2014-06-12 1:21 ` Dave Chinner
2014-06-12 1:37 ` Dave Chinner
2014-06-12 2:32 ` Chris Murphy
2014-06-15 22:34 ` [systemd-devel] " Lennart Poettering
2014-06-16 4:01 ` Chris Murphy
2014-06-16 4:38 ` cwillu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140616101448.GB18016@tango.0pointer.de \
--to=lennart@poettering.net \
--cc=1i5t5.duncan@cox.net \
--cc=kreijack@inwind.it \
--cc=linux-btrfs@vger.kernel.org \
--cc=russell@coker.com.au \
--cc=systemd-devel@lists.freedesktop.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).