KDE screensaver process keeps running in the background, eating graphics card resources

[Roman]

After upgrading to KUbuntu Saucy, I noticed that graphics performance may drop essentially after launching a screensaver.

In the system monitor I found that even if the screensaver is no longer shown on the visible screen, its process still runs in the background, taking about 10% of CPU resources and causing heavy load at the graphics card. The problem is solved by killing the screensaver process manually.

The system is KUbuntu 13.10 with all updates.
I am using Intel GM965/GL960 chipset (onboard GMA X3100 graphics).
The bug is not 100% reproducible, but the chance of leaving the screensaver in the background is high.
The GPU load can be tested with intel_gpu_top. Before launching the screensaver it only shows 3 counts that reach 100% load level, while the remaining counts show almost zero usage. After launching the screensaver, and getting out of it, the screensaver process may be left in the background, and then intel_gpu_top shows lots of GPU modules being 100% busy, even if the system is standby. The performance of KWin effects and other OpenGL applications remarkably degrades in this case.

I've seen this behaviour only with the intel card. I could not test the NVidia card in the same manner, because with these cards the screensaver just does not show up and does not look launched (that might be another bug).

I expect the screensaver to be correctly terminated after unlocking the screen, and it should not eat the resources of the GPU when it is not actually shown on the screen.

[Roman (m01brv)]

Same things remain after upgrading the graphics acceleration stack from "oibaf/graphics-drivers" ppa. No visible differences between using AccelMethod=uxa or sna, and no difference with DRI=ilo

[Harald Sitter (apachelogger)]

Hi there!

Thanks for reporting this bug! Your bug seems to be a problem with the KDE program itself, and not with our KDE packages. While we appreciate your issue, it would be better if it was tracked at https://bugs.kde.org, so that the KDE developers can deal with this speedily and have direct communication with you as the reporter for more effective debugging.

Thanks!

[Roman (m01brv)]

Just discovered that this bug also affects NVidia cards. The screensaver itself never shows up, but its process silently runs in the background, even after the screen is ulocked.

[Roman (m01brv)]

Just a notice for anyone getting here: I found this bug at bugs.kde.org under the id of 323064