[regression] Ubuntu boots very slowly after kernel upgrading

[Gannet]

My Ubuntu VM started to boot very slowly immediately after it has been upgraded to linux 4.15.0-24. So it seems it is a regression. With 4.15.0-23 it boots normally.

~$ uname -a
Linux 1C-Q35 4.15.0-24-generic #26-Ubuntu SMP Wed Jun 13 08:44:47 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

~$ cat /proc/version_signature
Ubuntu 4.15.0-24.26-generic 4.15.18

~$ systemd-analyze blame
   11min 41.457s plymouth-quit-wait.service
          5.684s srv1cv83.service
          1.601s networkd-dispatcher.service
          1.491s NetworkManager.service
          1.336s udisks2.service
          1.295s ModemManager.service
          1.255s accounts-daemon.service
          1.121s thermald.service
          1.082s grub-common.service

~$ systemd-analyze critical-chain
The time after the unit is active or started is printed after the "@" character.
The time the unit takes to start is printed after the "+" character.

graphical.target @11min 43.954s
└─multi-user.target @11min 43.954s
  └─anacron.service @8min 58.982s
    └─basic.target @912ms
      └─paths.target @912ms
        └─cups.path @912ms
          └─sysinit.target @909ms
            └─apparmor.service @471ms +438ms
              └─local-fs.target @462ms
                └─run-user-1001-gvfs.mount @11min 24.915s
                  └─run-user-1001.mount @3.021s
                    └─swap.target @395ms
                      └─dev-disk-by\x2duuid-82c9d942\x2d61f4\x2d42fc\x2dbddc\x2dfdb02217509d.swap @378ms +16ms
                        └─dev-disk-by\x2duuid-82c9d942\x2d61f4\x2d42fc\x2dbddc\x2dfdb02217509d.device @378ms

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-24-generic 4.15.0-24.26
ProcVersionSignature: Ubuntu 4.15.0-24.26-generic 4.15.18
Uname: Linux 4.15.0-24-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: accountant 1136 F.... pulseaudio
CurrentDesktop: ubuntu:GNOME
Date: Wed Jul 4 23:17:49 2018
HibernationDevice: RESUME=UUID=82c9d942-61f4-42fc-bddc-fdb02217509d
InstallationDate: Installed on 2018-06-05 (29 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
IwConfig:
 lo no wireless extensions.

 enp1s0 no wireless extensions.
Lsusb:
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: QEMU Standard PC (Q35 + ICH9, 2009)
ProcFB: 0 qxldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-4.15.0-24-generic root=UUID=959b7c8f-048c-4d32-b999-f00713e22153 ro rootflags=subvol=@ quiet splash vt.handoff=1
RelatedPackageVersions:
 linux-restricted-modules-4.15.0-24-generic N/A
 linux-backports-modules-4.15.0-24-generic N/A
 linux-firmware 1.173.1
RfKill:

SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
WifiSyslog:

dmi.bios.date: 02/06/2015
dmi.bios.vendor: EFI Development Kit II / OVMF
dmi.bios.version: 0.0.0
dmi.chassis.type: 1
dmi.chassis.vendor: QEMU
dmi.chassis.version: pc-q35-2.11
dmi.modalias: dmi:bvnEFIDevelopmentKitII/OVMF:bvr0.0.0:bd02/06/2015:svnQEMU:pnStandardPC(Q35+ICH9,2009):pvrpc-q35-2.11:cvnQEMU:ct1:cvrpc-q35-2.11:
dmi.product.name: Standard PC (Q35 + ICH9, 2009)
dmi.product.version: pc-q35-2.11
dmi.sys.vendor: QEMU

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.