Xscreensaver produces high cpu and fan on 18.04

[lotuspsychje]

Ubuntu 18.04.4 with kernel 5.3.0-28-generic up to date @ 6/2/2020

Xscreensaver makes the system rise in high cpu load and high fan blowing

it always worked fine for years till recently this start to occur

tested both on gnome3 and openbox

tested a few screensavers, glmatrix, phosphor

after Xscreensaver launches getting alot of errors after a few minutes like these:

[ 1599.969906] mce: CPU1: Core temperature above threshold, cpu clock throttled (total events = 40)
[ 1599.969907] mce: CPU3: Core temperature above threshold, cpu clock throttled (total events = 40)
[ 1599.969909] mce: CPU3: Package temperature above threshold, cpu clock throttled (total events = 224)

to rule out its hardware related, i tested booting from grub with break=init
where the cpu stays 26c and no fans rise

disabling Xscreensaver keeps the system normal cpu & fan again

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xscreensaver 5.36-1ubuntu1
ProcVersionSignature: Ubuntu 5.3.0-28.30~18.04.1-generic 5.3.13
Uname: Linux 5.3.0-28-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.9
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Thu Feb 6 11:19:28 2020
InstallationDate: Installed on 2019-05-18 (263 days ago)
InstallationMedia: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
SourcePackage: xscreensaver
UpgradeStatus: No upgrade log present (probably fresh install)

[lotuspsychje (lotuspsychje)]

Still happens on 20.04 all up to date on kernel 5.4.0-70-generic (on the intel NUC)

But on my laptop with intel HD 620 graphics i cannot reproduce this

[Gary van der Merwe (garyvdm)]

I think I'm getting the same bug.

20.04 Linux: 5.8.0-55-generic xscreensaver: 5.42+dfsg1-1ubuntu1

I'm configured to run glslideshow

If I run `xscreensaver & xscreensaver-command -activate` I get high CPU on processes glslideshow and XOrg

If I run `/usr/lib/xscreensaver/glslideshow` directly, the CPU is low.

I've attached log's by running `xscreensaver -verbose` with `glslideshow -debug`

[Gary van der Merwe (garyvdm)]

Please ignore the above comment. It seems what I'm experiencing is a different bug.

If I run the following, I get high CPU

  glslideshow -delay 0 -zoom 100 -pan 1

If I run the following, I get low CPU

  glslideshow -zoom 100

[Tormod Volden (tormodvolden)]

Certain combinations of screensaver hacks, graphic drivers and cards cause unexpectedly high CPU loads. In my PPA at https://launchpad.net/~tormodvolden/+archive/ubuntu/ppa there is xscreensaver 5.45 for focal, with an extra patch that displays a CPU load summary for each hack in the verbose log. I hope this can help to collect more data.