linux-ext4 - [Bug 203247] jbd2 gets stuck at jbd2_journal_commit

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Message-ID: <bug-203247-13602-N2POZJJl9p@https.bugzilla.kernel.org/>
Date:   Mon, 15 Apr 2019 21:09:49 +0000
From:   bugzilla-daemon@...zilla.kernel.org
To:     linux-ext4@...r.kernel.org
Subject: [Bug 203247] jbd2 gets stuck at jbd2_journal_commit_transaction
 frequently

https://bugzilla.kernel.org/show_bug.cgi?id=203247

Theodore Tso (tytso@....edu) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |INVALID

--- Comment #11 from Theodore Tso (tytso@....edu) ---
Looking at your iostat -x output, /dev/sda is completely utilized:

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s 
sda               0.00  1154.00   47.00  836.00   864.00 10076.00    

avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
24.78    136.46     116.05  331.72  103.93   1.13 100.00

Note the 100% utilization and the average queue size of 136.46 I/O requests.  
So as I said, this sounds like I/O overload.   Your workload is simply issuing
more I/O than the disk can handle.   Why is going to be a userspace issue.

If you don't care about stale data (e.g., belonging to deleted files, which may
have privacy issues if you care about GDPR, HIPPA, PCI, etc. mandates) you
could try mounting with the mount option "data=writeback".  It could be that
updating to a newer version of the kernel (4.9.86 is quite antique, and you're
probably missing all sorts of security and otehr bug fixes) and a newer
userspace, and then setting up a new set of file systems formatted with ext4
will also help performance.   Or there might be something going on with
userspace writes to /dev/sda that shouldn't be happening or which could be
optimized away.

But I don't see anything here which is a kernel bug.

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