Compiz lag and high cpu usage with 15.x kernel including Spectre + Meltdown patches.

[John Boero]

I've been running Fedora smoothly with KDE Plasma 5 + Compiz for years. Currently latest F27 fully updated. I'm on Westmere Xeons and AMD Radeon RX 470 using the kernel's built-in amdgpu driver.

I recently noticed with the 4.15 kernels that my whole screen lags occasionally (1-2 seconds for mouse/key input to start showing up). I see Xorg varying wildly between 20-80% CPU usage. If I reboot to kernel 4.13.9 it all returns to normal performance. Furthermore in 4.15.x if I switch WM from Compiz to Marco it also returns to normal stability (0-3% Xorg CPU).

I can verify no changes to settings - VSync off, hardware renderer, etc. Performance will be smooth for a few seconds at a time but suddenly get choppy and lag for up to 2 seconds. I will continue to try to profile Xorg to see what's happening.

Anybody else having this?

[Alex ARNAUD (alexarnaud)]

What version of Compiz are you using? If you're using the one in the Fedora repository, it's compiz-reloaded, a fork of Compiz 0.8. Here we're talking only about Compiz 0.9 branch get from launchpad.

Best regards,
Alex.

[John Boero (boeroboy)]

Installed Packages
Name : compiz
Epoch : 1
Version : 0.8.14
Release : 3.fc27
Arch : x86_64
Size : 6.3 M
Source : compiz-0.8.14-3.fc27.src.rpm
Repo : @System
From repo : fedora

[John Boero (boeroboy)]

OK interesting is there a better place to post this?

I'll try to reproduce with 0.9 somehow.

[Alex ARNAUD (alexarnaud)]

The right place is https://github.com/compiz-reloaded

Could you close this bug as it is not relevant because we're not Compiz reloaded team.

Best regards,
Alex.

[John Boero (boeroboy)]

Closed as this is a downstream issue of 0.8.x reloaded

[KRopa (ubuntu-59m)]

FWIW, I have noticed similar behavior also. I am using Compiz 0.9 on my Arch Linux box with 4.15 kernel, NVidia card and drivers.

Besides the occasional 1-2 second lag to "wake up" the screen after LightDM unlock, I have encountered a total freeze of video response, where even CTRL+ALT+F3 switching to an alternate terminal just ends up with a blank screen.

I assumed it could be due to the Spectre + Meltdown patches, updates to the NVidia driver, kernel update, or Compiz... lots of potential causes.

I found that the problem was significantly reduced by simply re-installing Compiz 0.9 following the NVidia driver update. Also I disabled WebGL in Chromium.

[John Boero (boeroboy)]

Thanks @KRopa for confirming. I'm starting to notice this behavior in anything that is full-screen OpenGL intensive. Must be a general regression in Xorg or drivers. Only way I've found to remediate it is to disable page table isolation (pti=off kernel param) but that effectively leaves you vulnerable.