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From:   Neal Gompa <neal@gompa.dev>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     David Sterba <dsterba@suse.com>, David Sterba <dsterba@suse.cz>,
        linux-kernel@vger.kernel.org, Rafael Wysocki <rafael@kernel.org>,
        Chris Mason <clm@meta.com>, Boris Burkov <boris@bur.io>,
        regressions@leemhuis.info, regressions@lists.linux.dev,
        Neal Gompa <neal@gompa.dev>
Subject: Re: Linux regressions report for mainline [2023-04-16]
Date:   Tue, 18 Apr 2023 17:32:28 -0400
Message-Id: <20230418213228.1273218-1-neal@gompa.dev>
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References: <CAHk-=wjL7GG9s9Y2+u2725M+Ru=bUXnzOnXRwoSktY0fVdhhzw@mail.gmail.com>
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Hi Linus and David,

I'm the guy that sort of kickstarted this whole thing a year ago.
From my perspective in Fedora-land, we've been running automatic
weekly fstrim on every Fedora system for three years now[1] and
have not received any complaints about SSDs pushing daises from
that.

When we started discussing btrfs discard=async within Fedora
two years ago[2], I started soliciting feedback and information
from the Btrfs developers I was regularly working with at the time.

Last year, I had a face-to-face with Chris Mason and we discussed
the idea in depth and decided to go for this, based on both Fedora's
data with consumer disks and Facebook's data with their datacenters.

The only real surprise we had was the so-called "discard storm",
which Boris Burkov made adjustments to resolve a couple weeks ago[3].

With all that context in mind, I'm not sure we really should be panicking
about having async discard enabled, since it's the same operation
that the fstrim timer was doing before, just queued by btrfs itself instead.

So personally, I would prefer *not* to revert the new default.

Thanks in advance and best regards,
Neal

[1]: https://fedoraproject.org/wiki/Changes/EnableFSTrimTimer
[2]: https://pagure.io/fedora-btrfs/project/issue/6
[3]: https://lore.kernel.org/linux-btrfs/cover.1680723651.git.boris@bur.io/T/#t


-- 
真実はいつも一つ！/ Always, there's only one truth!