Bug 344175 - While switched from an X KDE session to an alternate virtual terminal, kwin uses 100% CPU, usually.
Summary: While switched from an X KDE session to an alternate virtual terminal, kwin u...
Status: RESOLVED DUPLICATE of bug 330954
Alias: None
Product: kwin
Classification: Plasma
Component: general (show other bugs)
Version: unspecified
Platform: Arch Linux Linux
: NOR normal
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2015-02-14 20:10 UTC by James
Modified: 2015-02-15 04:25 UTC (History)
0 users

See Also:
Latest Commit:
Version Fixed In:

Attachments
Add an attachment

Note You need to log in before you can comment on or make changes to this bug.
Description James 2015-02-14 20:10:52 UTC 
Arch Linux
kdebase-workspace 4.11.16-1

$ kwin -v
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbehave.
Qt: 4.8.6
KDE Development Platform: 4.14.5
KWin: 4.11.16

AMD Phenom 8400 Triple-Core Processor
AMD/ATI Redwood PRO Radeon HD 5570
running two displays

When and while switched to another Virtual Terminal - where in Arch Linux, Xorg runs in the same VT where it is started - and whether logged into the VT or not, kwin will often, but not always, use 100% CPU on one core.  Switching back to X KDE seems to always return CPU usage to normal.

Reproducible: Sometimes

Steps to Reproduce:
1.Ctrl-Alt-F2
2.
3.

Actual Results:  
kwin uses 100% CPU on one core.

Expected Results:  
kwin CPU usage decreases.
Comment 1 Thomas Lübking 2015-02-14 20:32:38 UTC 
please attach the output of
qdbus org.kde.KWin /KWin supportInformation

This is (likely) due to vertical sync, the driver will perform a busy wait for a retrace that does never occur.
As workaround, suspend compositing before switching VT.

Pre-emptive duping.

*** This bug has been marked as a duplicate of bug 330954 ***
Comment 2 James 2015-02-15 04:25:01 UTC 
I am posting to Bug 330954.