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Date:   Mon, 21 Jun 2021 17:50:07 -0700
From:   Josh Triplett <josh@joshtriplett.org>
To:     Andreas Dilger <adilger@dilger.ca>
Cc:     David Howells <dhowells@redhat.com>, Theodore Ts'o <tytso@mit.edu>,
        "Darrick J. Wong" <djwong@kernel.org>, Chris Mason <clm@fb.com>,
        Ext4 Developers List <linux-ext4@vger.kernel.org>,
        xfs <linux-xfs@vger.kernel.org>,
        linux-btrfs <linux-btrfs@vger.kernel.org>,
        linux-cachefs@redhat.com,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        NeilBrown <neilb@suse.com>
Subject: Re: How capacious and well-indexed are ext4, xfs and btrfs
 directories?
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On Tue, May 25, 2021 at 03:13:52PM -0600, Andreas Dilger wrote:
> There was a patch pushed recently that targets "-o discard" performance:
> https://patchwork.ozlabs.org/project/linux-ext4/list/?series=244091
> that needs a bit more work, but may be worthwhile to test if it improves
> your workload, and help put some weight behind landing it?

I just got a chance to test that patch (using the same storage stack,
with ext4 atop dm-crypt on the same SSD). That patch series makes a
*massive* difference; with that patch series (rebased atop latest
5.13.0-rc7) and the test case from my previous mail, `rm -r testdir`
takes the same amount of time (~17s) whether I have discard enabled or
disabled, and doesn't disrupt the rest of the system.  Without the
patch, that same removal took many minutes, and stalled out the rest of
the system.

Thanks for the reference; I'll follow up to the thread for that patch
with the same information.

- Josh Triplett