Very slow Xorg performace when drawing Qt5's QPainter
Submitted by mad..@..las.cz
Assigned to xf86-video-ati maintainers
Description
Created attachment 113671
MWE
My Qt5 based application updates contents of a widget as the mouse moves over it. Unfortunately the drawing operation causes inexplicably high load and everything slows down to a crawl. During that time I observe Xorg fully loading one CPU core, the application itself does not seem to consume much CPU. My entire desktop is almost unusable until Xorg sorts itself out after a few seconds.
As of now I found two possible workarounds:
- Use Qt4 toolkit instead of Qt5
- Set "Option" "NoAccel" to "true" in Xorg.conf
I believe that this issue has to do with either GLAMOR or xf86-ati drivers because the application behaves normally on a machine with nVidia card or in Windows.
I attached a small MWE which demonstrates the problem. Build the MWE with Qt5 toolkit, maximize the window and move mouse over the green area.
Up-to-date Fedora 21
xorg-x11-server 1.16.3
mesa 10.4.3
xorg-x11-drv-ati 7.5.0
**Attachment 113671**, "MWE":
QPSlowMWE.tar.xz