Machine is a Ryzen 3600 with a Nvidia GT710 installed. Clean install of bullseye using DI RC3. Install proceeded without issue. When prompted by tasksel selected mate-desktop and ssh server options (everything else de-selected).

After reboot, adjusted sources.list to include contrib and non-free. Installed nvidia-driver package. Removed libreoffice and aspell packages. Added an iptables based firewall.

Mate system monitor show all 16 CPU cores using up to 20% CPU usage. I've tried attaching a screenshot. Top shows a number of mate components mostly sleeping, but all using some percentage of CPU. dbus-daemon is always at the top of the list. If user logs out of desktop these go away (ie watch it via ssh).


top - 14:00:15 up 5 min,  2 users,  load average: 1.05, 0.42, 0.16
Tasks: 209 total,   1 running, 208 sleeping,   0 stopped,   0 zombie
%Cpu(s):  8.6 us,  1.5 sy,  0.0 ni, 88.7 id,  0.0 wa,  0.0 hi,  1.2 si,  0.0 st
MiB Mem :  15982.1 total,  15241.1 free,    422.2 used,    318.8 buff/cache
MiB Swap:    976.0 total,    976.0 free,      0.0 used.  15286.3 avail Mem

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
    864 root      20   0    8216   4668   3776 S   8.0   0.0   0:08.46 dbus-daemon
    646 root      20   0  267964  62360  44652 S   2.7   0.4   0:03.97 Xorg
    854 root      20   0  270052  24896  17164 S   2.0   0.2   0:02.49 x-session-manag
    927 root      20   0  236904   9568   6628 S   1.3   0.1   0:01.16 gvfsd
    851 root      20   0  237352   7652   6704 S   1.0   0.0   0:01.01 gnome-keyring-d
    905 root      20   0    7804   4272   3816 S   1.0   0.0   0:01.30 dbus-daemon
    917 root      20   0  839236  58200  40764 S   1.0   0.4   0:01.26 mate-settings-d
    920 root      20   0  165804   6724   6052 S   1.0   0.0   0:01.00 at-spi2-registr
    961 root      20   0  270196  22544  17172 S   1.0   0.1   0:00.57 mate-screensave
    976 root      20   0  348988  11864  10464 S   1.0   0.1   0:01.26 gvfs-udisks2-vo
    991 root      20   0  311684  10020   6792 S   1.0   0.1   0:01.18 gvfs-afc-volume
    996 root      20   0  233000   8428   5460 S   1.0   0.1   0:01.19 gvfs-mtp-volume
   1000 root      20   0  235372   7160   6212 S   1.0   0.0   0:01.18 gvfs-gphoto2-vo
   1004 root      20   0  233072   6268   5636 S   1.0   0.0   0:01.20 gvfs-goa-volume
  13705 root      20   0  379612  27368  21440 S   1.0   0.2   0:00.03 caja
    966 root      20   0  189456  15660  13884 S   0.7   0.1   0:00.48 polkit-mate-aut
    926 root      20   0  320304  38940  28408 S   0.3   0.2   0:00.52 marco
    937 root      20   0  469580  44108  32048 S   0.3   0.3   0:00.76 mate-panel
    950 root      20   0  344692  29372  22564 S   0.3   0.2   0:00.17 wnck-applet
    959 root      20   0  473080  42696  33664 S   0.3   0.3   0:00.17 nm-applet
    978 root      20   0  342720  25308  19744 S   0.3   0.2   0:00.32 mate-power-mana
   1013 root      20   0  343076  27912  22172 S   0.3   0.2   0:00.14 notification-ar
      1 root      20   0  163876  10332   7868 S   0.0   0.1   0:00.79 systemd

I applied the official release ISO. Problem still exists. One has to login as root on the console to see the issue. If you login via ssh or even on the console as a normal user there is no issue.
I noticed that caja seems to start automatically (it’s shown in top) even though I have not attempted to use it. If one clicks on Application -> System tools -> caja the window typically won’t come up. It took me 4 tries before the window appeared. After exiting caja CPU usage dropped to 1% indicating some link to caja auto starting for root.