Desktop repeatedly unresponsive for 10 to 30 seconds


I have just upgraded to Ozymandias and am now facing a show stopper problem:
Very often (every 1/2 to 4 minutes, seems to depend on what I do)
the screen does not react anymore, for about 8 to 30 seconds.
My inputs during such a period will be recorded (e.g. keys entered into
a text field will appear after the freeze is over).

I have a second installation of Ozymandias (upgraded last week)
which behaves a little different.
There the lags occur much rarer (after one or several hours),
but last much longer (minutes).
This may be an unrelated phenomenon.

Are other people experiencing similar things?

Any ideas what may cause this?


Update on my experiences with the strange screen freeze:

Quite often the freeze endend, when I pressed Alt+Tab.
This cannot always have been a coincidence.


It seems to be this bug:

Seems to be a driver issue or kwin issue. We have already some intel fixes in place on Netrunner 16 to avoid intel/kwin bugs. Though that might not help with every effect activated.
I’ll keep watching this bug to see if there is any fix for that coming up.

For the time being I would suggest trying disabling some effects (one after another) to see if it makes it better.
I personally would start with disabling the blur effect (as in my experience thats the most problematic effect when it comes to driver issues)
The fast workaround would be disabling effects alltogether and running a non composite desktop.

Yes, disabling compositing altogether is what I did now, and that seems to avoid this issue completely
on one machine. We can live with that quite well, so I won’t investigate this setup any further.

On my other machine, I cannot test this, because it is stuck in the “black screen” problem (i.e.
immediately after session start the screen turns black and stays black except for the pointer arrow,
which can be moved)


Because the freeze of the whole desktop (except mouse arrow) does not occur anymore,
I can now say that the freeze of the control bar must be a separate problem, because, for example,
right at this moment the control bar has been staying in a frozen state for over twenty minutes.
I guess, I should open another thread for that.


Now the control panel came back to life again. After 32 minutes!!
And it has executed all the actions that I had tried within the last half hour (activating windows,
clicking the clock, opening applications…).