glamor causes stuttering on a specific KDE UI component - Kirigami ScrollBar

[arrowd]

Describe the bug

1. Install the minimal KDE software required to reproduce the issue: pkg install plasma5-kde-cli-tools plasma5-plasma-desktop.
2. Run kcmshell5 kcm_plasmasearch.
3. Maximize the window for better reproducibility.
4. Move mouse cursor to the rightmost scrollbar.
5. Click and hold the scrollbar handle.
6. Without releasing the button move the cursor to the bottom of the scrollbar lane.

The scrolling animation is extremely stuttering. It takes only 2-3 frames for handle to reach the bottom. On some of our machines it is even worse - if you move the handle slowly but steady (without micro-stops) the window content isn't updated at all until you either release the button or stop the movement.

This behavior reproduces on 14-CURRENT, i915kms and drm-515-kmod as well as 13.2-RC6, amdgpu and drm-510-kmod.

Now, starting X server with the following config makes the problem go away:

Section "Device"
  Driver     "modesetting"
  Identifier "asdasd"
  Option "AccelMethod" "none"
EndSection

FreeBSD version

FreeBSD sbreeze 14.0-CURRENT FreeBSD 14.0-CURRENT #21 main-n261572-3451ed888e75: Tue Mar 21 20:33:52 +03 2023
root@sbreeze:/usr/obj/usr/src/amd64.amd64/sys/AMENITY amd64

PCI Info

pciconf -lv

``` hostb0@pci0:0:0:0: class=0x060000 rev=0x05 hdr=0x00 vendor=0x8086 device=0x5910 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = 'Xeon E3-1200 v6/7th Gen Core Processor Host Bridge/DRAM Registers' class = bridge subclass = HOST-PCI pcib1@pci0:0:1:0: class=0x060400 rev=0x05 hdr=0x01 vendor=0x8086 device=0x1901 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = '6th-10th Gen Core Processor PCIe Controller (x16)' class = bridge subclass = PCI-PCI vgapci1@pci0:0:2:0: class=0x030000 rev=0x04 hdr=0x00 vendor=0x8086 device=0x591b subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = 'HD Graphics 630' class = display subclass = VGA none0@pci0:0:8:0: class=0x088000 rev=0x00 hdr=0x00 vendor=0x8086 device=0x1911 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = 'Xeon E3-1200 v5/v6 / E3-1500 v5 / 6th/7th/8th Gen Core Processor Gaussian Mixture Model' class = base peripheral xhci0@pci0:0:20:0: class=0x0c0330 rev=0x31 hdr=0x00 vendor=0x8086 device=0xa12f subvendor=0x1043 subdevice=0x201f vendor = 'Intel Corporation' device = '100 Series/C230 Series Chipset Family USB 3.0 xHCI Controller' class = serial bus subclass = USB pchtherm0@pci0:0:20:2: class=0x118000 rev=0x31 hdr=0x00 vendor=0x8086 device=0xa131 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = '100 Series/C230 Series Chipset Family Thermal Subsystem' class = dasp ig4iic0@pci0:0:21:0: class=0x118000 rev=0x31 hdr=0x00 vendor=0x8086 device=0xa160 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = '100 Series/C230 Series Chipset Family Serial IO I2C Controller' class = dasp none1@pci0:0:22:0: class=0x078000 rev=0x31 hdr=0x00 vendor=0x8086 device=0xa13a subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = '100 Series/C230 Series Chipset Family MEI Controller' class = simple comms ahci0@pci0:0:23:0: class=0x010601 rev=0x31 hdr=0x00 vendor=0x8086 device=0xa103 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = 'HM170/QM170 Chipset SATA Controller [AHCI Mode]' class = mass storage subclass = SATA pcib2@pci0:0:28:0: class=0x060400 rev=0xf1 hdr=0x01 vendor=0x8086 device=0xa112 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = '100 Series/C230 Series Chipset Family PCI Express Root Port' class = bridge subclass = PCI-PCI pcib3@pci0:0:28:3: class=0x060400 rev=0xf1 hdr=0x01 vendor=0x8086 device=0xa113 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = '100 Series/C230 Series Chipset Family PCI Express Root Port' class = bridge subclass = PCI-PCI pcib4@pci0:0:28:6: class=0x060400 rev=0xf1 hdr=0x01 vendor=0x8086 device=0xa116 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = '100 Series/C230 Series Chipset Family PCI Express Root Port' class = bridge subclass = PCI-PCI isab0@pci0:0:31:0: class=0x060100 rev=0x31 hdr=0x00 vendor=0x8086 device=0xa152 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = 'HM175 Chipset LPC/eSPI Controller' class = bridge subclass = PCI-ISA none2@pci0:0:31:2: class=0x058000 rev=0x31 hdr=0x00 vendor=0x8086 device=0xa121 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = '100 Series/C230 Series Chipset Family Power Management Controller' class = memory hdac0@pci0:0:31:3: class=0x040380 rev=0x31 hdr=0x00 vendor=0x8086 device=0xa171 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = 'CM238 HD Audio Controller' class = multimedia subclass = HDA ichsmb0@pci0:0:31:4: class=0x0c0500 rev=0x31 hdr=0x00 vendor=0x8086 device=0xa123 subvendor=0x1043 subdevice=0x15e0 vendor = 'Intel Corporation' device = '100 Series/C230 Series Chipset Family SMBus' class = serial bus subclass = SMBus vgapci0@pci0:1:0:0: class=0x030200 rev=0xa1 hdr=0x00 vendor=0x10de device=0x1c8c subvendor=0x1043 subdevice=0x15e0 vendor = 'NVIDIA Corporation' device = 'GP107M [GeForce GTX 1050 Ti Mobile]' class = display subclass = 3D iwm0@pci0:2:0:0: class=0x028000 rev=0x59 hdr=0x00 vendor=0x8086 device=0x095a subvendor=0x8086 subdevice=0x5010 vendor = 'Intel Corporation' device = 'Wireless 7265' class = network re0@pci0:3:0:0: class=0x020000 rev=0x15 hdr=0x00 vendor=0x10ec device=0x8168 subvendor=0x1043 subdevice=0x200f vendor = 'Realtek Semiconductor Co., Ltd.' device = 'RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller' class = network subclass = ethernet rtsx0@pci0:4:0:0: class=0xff0000 rev=0x01 hdr=0x00 vendor=0x10ec device=0x5229 subvendor=0x1043 subdevice=0x202f vendor = 'Realtek Semiconductor Co., Ltd.' device = 'RTS5229 PCI Express Card Reader' ```

DRM KMOD version drm-515-kmod 5.15.25_2

Screenshots Another window that has this problem is kcmshell5 kcm_kwin_effects. Here is a video of the debugging session for that window. We added a textbox that reacts on mouse event and displays its current position. It shows that stuttering is happening even without mouse clicks, just hovering over the scrollbar is enough. Note the cursor movements on 0:06-0:10 - this is the same freeze that prevents scrolling animation if the button is pressed.

Additional context I have reports that it also works fine with NVIDIA proprietary driver.

[arrowd]

I'll be happy do research/debug this on my own, but I need some starting point at least.

[evadot]

I can't seem to reproduce this here on a valleyview machine with 5.10 (5.15 doesn't work yet on this one), will try on some other systems.

[arrowd]

Hi @evadot , thanks for checking this out. Were you able to conduct testing on 5.15?

[evadot]

Not yet, will try to find time.

[kblc]

Hi there! ) any update?

[arrowd]

I wonder if this has something to do with "complex shaders". I stumbled upon this MR https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1171 which talks about it.