[radeon] Xorg high CPU usage and stuttering in XFCE on Ubuntu 20.04

[David Santinoli]

After upgrading Xubuntu from 19.10 to 20.04, some window operations (e.g. bringing one to foreground) can take an unusually long time (tenths of second, enough to compromise the general responsiveness of the system).
Even switching from one terminal window to another causes a 80-90% CPU spike due to Xorg. (Tested with xfce4-terminal as well as rxvt.)

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: xorg 1:7.7+19ubuntu14
ProcVersionSignature: Ubuntu 5.4.0-29.33-generic 5.4.30
Uname: Linux 5.4.0-29-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
BootLog:

CasperMD5CheckResult: skip
CompositorRunning: None
CurrentDesktop: XFCE
Date: Sat May 16 11:12:32 2020
DistUpgraded: 2020-05-09 17:20:01,127 DEBUG Running PostInstallScript: './xorg_fix_proprietary.py'
DistroCodename: focal
DistroVariant: ubuntu
EcryptfsInUse: Yes
ExtraDebuggingInterest: Yes
GraphicsCard:
 Advanced Micro Devices, Inc. [AMD/ATI] RS880 [Radeon HD 4290] [1002:9714] (prog-if 00 [VGA controller])
   Subsystem: ASUSTeK Computer Inc. RS880 [Radeon HD 4290] [1043:8454]
MachineType: System manufacturer System Product Name
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.4.0-29-generic root=UUID=7ac7906b-f137-4adf-9de3-2ec128242354 ro
SourcePackage: xorg
Symptom: display
UpgradeStatus: Upgraded to focal on 2020-05-09 (6 days ago)
dmi.bios.date: 04/13/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 1301
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: M4A89GTD-PRO
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: Rev 1.xx
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr1301:bd04/13/2010:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnM4A89GTD-PRO:rvrRev1.xx:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.family: To Be Filled By O.E.M.
dmi.product.name: System Product Name
dmi.product.sku: To Be Filled By O.E.M.
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer
modified.conffile..etc.default.apport: [modified]
mtime.conffile..etc.default.apport: 2017-10-10T22:39:42.917279
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.101-2
version.libgl1-mesa-dri: libgl1-mesa-dri 20.0.4-2ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx 20.0.4-2ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.20.8-2ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.6-1
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:19.1.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20200226-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.16-1

[Daniel van Vugt (vanvugt)]

Please run 'top' in a terminal to confirm it is the 'Xorg' process using the most CPU.

[David Santinoli (dav9o)]

Did that before filing the bug report, Xorg is the top CPU user.

[Daniel van Vugt (vanvugt)]

1. Is the high CPU usage sustained when you're not doing anything?

2. Is the CPU usage only when using a mouse, or does it also occur when using a keyboard?

[David Santinoli (dav9o)]

> 1. Is the high CPU usage sustained when you're not doing anything?

No.

> 2. Is the CPU usage only when using a mouse, or does it also occur when using a keyboard?

In both cases. For example, Xorg's CPU usage jumps to 85% on my machine when I continuously switch once per second from one terminal window to another, regardless of the means (mouse or ALT+TAB).

On the other hand, merely typing (albeit fast) into a terminal window leads to a much lesser usage by Xorg (around 10%).

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.