Fresh RCs for 18.04.3 -- Please Test

Paul Richards paul.richards at
Tue Aug 6 14:26:00 UTC 2019

I had a look at the same image as Ian:

72491db7ef6f3cd4b085b9fe1f232345 *bionic-desktop-amd64.iso

I was mostly curious about single queue devices now defaulting to the
multi queue IO scheduler framework (previously they used the legacy IO
schedulers - ).  I was also
interested to see how the udev rules might work to select an
appropriate multiqueue scheduler for nvme / ssd / hdd.

What I found:

1. There are no udev rules for different devices, but my ssd and hdd
defaulted to a sensible multiqueue scheduler anyway (both using

2. With 18.04.2 my SATA disks used the legacy "cfq" scheduler by
default, and with 18.04.3 they use "mq-deadline" by default.

So my quesions are:

1. Will the transition to a multi-queue IO scheduler default be called
out in the release notes for 18.04.3?  There are two possible
surprises for users.  First, as I understand it the spiritual
successor to "cfq" should be "bfq", not "mq-deadline".  Second, any
18.04.2 users who have set grub boot parameters to select which legacy
IO scheduler to use will find their parameter no longer working as
they now need to configure multi-queue parameters instead.

2. Will the Ubuntu "IOSchedulers" wiki page be updated wrt 18.04.3?  ( )  It says
things like "Prior to Ubuntu 19.10..", which will need updated.  (I
think this wiki page was already uncorrect, surely it should have said
"Prior to Ubuntu 19.04" ?)

3. Just for my own curiosity, how does Ubuntu 18.04.3 select a default
mq scheduler without udev rules like other distros do (e.g. Arch -
) ?

On Mon, 5 Aug 2019 at 21:12, Adam Conrad <adconrad at> wrote:
> Fresh RCs for 18.04.3 have been spun up and posted to the ISO tracker
> today, and these ones are the Real Deal.  The volume labels are set
> and base-files is updated, and barring any showstoppers, these are
> what I expect to release on Thursday.
> So, please, pick your favourite flavour and get testing.  Do keep in
> mind that any bug that was also present in 18.04.2 isn't considered
> a blocker, and minor regressions can be dealt with post-release, but
> if you find something dire and boot/install critical, we need to hear
> about it yesterday so we can get it sorted by release.
> Thanks in advance, and happy testing,
> ... Adam
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