Bug#893717: gnome-shell: Poor performance with wayland after upgrading to 3.28

[Sam Morris]

Package: gnome-shell
Version: 3.28.0-1
Severity: normal

Since upgrading to 3.28, performance of gnome-shell as a wayland
compositor is very bad. It seems that drawing to the screen causes a
brief stutter that is easy to observe by moving the mouse cursor over
regions that react to being hovered over.

Compare how smoothly the mouse cursor moves in the following two videos:

https://youtu.be/KJbrkJsqcSk
https://youtu.be/O-rR6u9ukN8

The first video is using wayland, the second Xorg. This is on a Lenovo
P50 with (regretably) an NVIDIA card:

	01:00.0 VGA compatible controller: NVIDIA Corporation GM107GLM [Quadro M2000M] (rev a2)

I've tried to reproduce this with Xwayland running under weston, and
performance seems fine, so I'm suspecting gnome-shell/mutter or a
dependency at this stage.

-- System Information:
Debian Release: buster/sid
  APT prefers testing-debug
  APT policy: (570, 'testing-debug'), (570, 'testing'), (540, 'unstable-debug'), (540, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.15.0-1-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages gnome-shell depends on:
ii  dconf-gsettings-backend [gsettings-backend]  0.26.1-3
ii  evolution-data-server                        3.26.5-2
ii  gir1.2-accountsservice-1.0                   0.6.45-1
ii  gir1.2-atspi-2.0                             2.28.0-1
ii  gir1.2-freedesktop                           1.54.1-4
ii  gir1.2-gcr-3                                 3.28.0-1
ii  gir1.2-gdesktopenums-3.0                     3.28.0-1
ii  gir1.2-gdm-1.0                               3.28.0-1
ii  gir1.2-geoclue-2.0                           2.4.7-1
ii  gir1.2-glib-2.0                              1.54.1-4
ii  gir1.2-gnomebluetooth-1.0                    3.28.0-2
ii  gir1.2-gnomedesktop-3.0                      3.27.92-1
ii  gir1.2-gtk-3.0                               3.22.29-1
ii  gir1.2-gweather-3.0                          3.28.0-2
ii  gir1.2-ibus-1.0                              1.5.17-3
ii  gir1.2-mutter-2                              3.28.0-1
ii  gir1.2-nm-1.0                                1.10.6-2
ii  gir1.2-nma-1.0                               1.8.10-2
ii  gir1.2-pango-1.0                             1.40.14-1
ii  gir1.2-polkit-1.0                            0.105-18
ii  gir1.2-rsvg-2.0                              2.40.20-2
ii  gir1.2-soup-2.4                              2.62.0-1
ii  gir1.2-upowerglib-1.0                        0.99.7-2
ii  gjs                                          1.50.3-2
ii  gnome-backgrounds                            3.28.0-1
ii  gnome-settings-daemon                        3.26.2-1+b1
ii  gnome-shell-common                           3.28.0-1
ii  gsettings-desktop-schemas                    3.28.0-1
ii  libatk-bridge2.0-0                           2.26.2-1
ii  libatk1.0-0                                  2.28.1-1
ii  libc6                                        2.27-2
ii  libcairo2                                    1.15.10-1
ii  libcanberra-gtk3-0                           0.30-6
ii  libcanberra0                                 0.30-6
ii  libcroco3                                    0.6.12-2
ii  libecal-1.2-19                               3.26.5-2
ii  libedataserver-1.2-22                        3.26.5-2
ii  libgcr-base-3-1                              3.28.0-1
ii  libgdk-pixbuf2.0-0                           2.36.11-1
ii  libgirepository-1.0-1                        1.54.1-4
ii  libgjs0g [libgjs0-libmozjs-52-0]             1.52.0-2
ii  libglib2.0-0                                 2.54.3-2
ii  libglib2.0-bin                               2.54.3-2
ii  libgstreamer1.0-0                            1.12.4-1
ii  libgtk-3-0                                   3.22.29-1
ii  libical3                                     3.0.1-5
ii  libjson-glib-1.0-0                           1.4.2-3
ii  libmutter-2-0                                3.28.0-1
ii  libnm0                                       1.10.6-2
ii  libpango-1.0-0                               1.40.14-1
ii  libpangocairo-1.0-0                          1.40.14-1
ii  libpolkit-agent-1-0                          0.105-18
ii  libpolkit-gobject-1-0                        0.105-18
ii  libpulse-mainloop-glib0                      11.1-4
ii  libpulse0                                    11.1-4
ii  libsecret-1-0                                0.18.5-6
ii  libstartup-notification0                     0.12-5
ii  libsystemd0                                  238-3
ii  libx11-6                                     2:1.6.4-3
ii  libxfixes3                                   1:5.0.3-1
ii  mutter                                       3.28.0-1
ii  python3                                      3.6.4-1

Versions of packages gnome-shell recommends:
ii  chrome-gnome-shell    9-1
ii  gdm3                  3.28.0-1
ii  gkbd-capplet          3.26.0-3
ii  gnome-control-center  1:3.28.0-1
ii  gnome-user-docs       3.28.0-1
ii  iio-sensor-proxy      2.4-2
ii  switcheroo-control    1.2-1
ii  unzip                 6.0-21

Versions of packages gnome-shell suggests:
ii  gir1.2-telepathyglib-0.12   0.24.1-2
ii  gir1.2-telepathylogger-0.2  0.8.2-3

-- no debconf information