From: Sitsofe Wheeler <sitsofe@gmail.com>
To: linux-fsdevel@vger.kernel.org
Cc: drh@sqlite.org
Subject: Questions about filesystems from SQLite author presentation
Date: Mon, 6 Jan 2020 07:24:53 +0000 [thread overview]
Message-ID: <CALjAwxi3ZpRZLS9QaGfAqwAVST0Biyj_p-b22f=iq_ns4ZQyiA@mail.gmail.com> (raw)
At Linux Plumbers 2019 Dr Richard Hipp presented a talk about SQLite
(https://youtu.be/-oP2BOsMpdo?t=5525 ). One of the slides was titled
"Things to discuss"
(https://sqlite.org/lpc2019/doc/trunk/slides/sqlite-intro.html/#6 )
and had a few questions:
1. Reliable ways to discover detailed filesystem properties
2. fbarrier()
3. Notify the OS about unused regions in the database file
For 1. I think Jan Kara said that supporting it was undesirable for
details like just how much additional fsync were needed due to
competing constraints (https://youtu.be/-oP2BOsMpdo?t=6063 ). Someone
mentioned there was a
patch for fsinfo to discover if you were on a network filesystem
(https://www.youtube.com/watch?v=-oP2BOsMpdo&feature=youtu.be&t=5525
)...
For 2. there was a talk by MySQL dev Sergei Golubchik (
https://youtu.be/-oP2BOsMpdo?t=1219 ) talking about how barriers had
been taken out and was there a replacement. In
https://youtu.be/-oP2BOsMpdo?t=1731 Chris Mason(?) seems to suggest
that the desired effect could be achieved with io_uring chaining.
For 3. it sounded like Jan Kara was saying there wasn't anything at
the moment (hypothetically you could introduce a call that marked the
extents as "unwritten" but it doesn't sound like you can do that
today) and even if you wanted to use something like TRIM it wouldn't
be worth it unless you were trimming a large (gigabytes) amount of
data (https://youtu.be/-oP2BOsMpdo?t=6330 ).
However, there were even more questions in the briefing paper
(https://sqlite.org/lpc2019/doc/trunk/briefing.md and search for '?')
that couldn't be asked due to limited time. Does anyone know the
answer to the extended questions and whether the the above is right
deduction for the questions that were asked?
--
Sitsofe | http://sucs.org/~sits/
next reply other threads:[~2020-01-06 7:25 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-06 7:24 Sitsofe Wheeler [this message]
2020-01-06 10:15 ` Questions about filesystems from SQLite author presentation Dave Chinner
2020-01-07 8:40 ` Sitsofe Wheeler
2020-01-07 8:55 ` Jan Kara
2020-01-07 17:18 ` Darrick J. Wong
2020-01-07 8:47 ` Jan Kara
2020-01-06 15:40 ` Amir Goldstein
2020-01-06 16:42 ` Matthew Wilcox
2020-01-07 9:28 ` Sitsofe Wheeler
2020-01-06 18:31 ` Amir Goldstein
2020-01-07 9:16 ` Jan Kara
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