From: David Sterba <dsterba@suse.cz>
To: Josef Bacik <josef@toxicpanda.com>
Cc: linux-btrfs@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 0/5] Fix up some stupid delayed ref flushing behaviors
Date: Wed, 25 Mar 2020 14:51:46 +0100 [thread overview]
Message-ID: <20200325135146.GA5920@twin.jikos.cz> (raw)
In-Reply-To: <20200313211220.148772-1-josef@toxicpanda.com>
On Fri, Mar 13, 2020 at 05:12:15PM -0400, Josef Bacik wrote:
> While debugging Zygo's delayed ref problems it was clear there were a bunch of
> cases that we're running delayed refs when we don't need to be, and they result
> in a lot of weird latencies.
>
> Each patch has their individual explanations. But the gist of it is we run
> delayed refs in a lot of arbitrary ways that have just accumulated throughout
> the years, so clean up all of these so we can have more consistent performance.
It would be fine to remove the delayed refs being run from so many
places but I vaguely remember some patches adding them with "we have to
run delayed refs here or we will miss something and that would be a
corruption". The changelogs in patches from 3 on don't point out any
specific problems and I miss some reasoning about correctness, ideally
for each line of btrfs_run_delayed_refs removed.
As a worst case I really don't want to get to a situation where we start
getting reports that something broke because of the missing delayed
refs, followed by series of "oh yeah I forgot we need it here, add it
back".
The branch with this patchset is in for-next but I'm still not
comfortable with adding it to misc-next as I can't convince myself it's
safe, so more reviews are welcome.
next prev parent reply other threads:[~2020-03-25 13:52 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-13 21:12 [PATCH 0/5] Fix up some stupid delayed ref flushing behaviors Josef Bacik
2020-03-13 21:12 ` [PATCH 1/5] btrfs: set delayed_refs.flushing for the first delayed ref flushing Josef Bacik
2020-03-13 21:12 ` [PATCH 2/5] btrfs: delayed refs pre-flushing should only run the heads we have Josef Bacik
2020-04-03 14:31 ` Nikolay Borisov
2020-03-13 21:12 ` [PATCH 3/5] btrfs: only run delayed refs once before committing Josef Bacik
2020-04-03 14:34 ` Nikolay Borisov
2020-03-13 21:12 ` [PATCH 4/5] btrfs: run delayed refs less often in commit_cowonly_roots Josef Bacik
2020-04-03 14:43 ` Nikolay Borisov
2020-03-13 21:12 ` [PATCH 5/5] btrfs: stop running all delayed refs during snapshot Josef Bacik
2020-04-03 14:46 ` Nikolay Borisov
2020-03-25 13:51 ` David Sterba [this message]
2020-03-25 14:12 ` [PATCH 0/5] Fix up some stupid delayed ref flushing behaviors Josef Bacik
2020-03-26 15:36 ` Zygo Blaxell
2020-03-26 19:58 ` Josef Bacik
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