Hi, I'm not sure if this is KDE related, so please direct me to the proper channels if possible.

I've noticed recently (probably in the upgrade from Kubuntu 12.10 to Kubuntu 13.04), that the screen occasionally glitches out, perhaps once every few days. The screen freezes for a few seconds, and then resumes. When it resumes, it refreshes extremely slowly. For example, alt-tabbing through Firefox windows looks terrible. Each new window takes a half seconds to appear, and I can see the screen drawing the window from the top down. It looks like it is drawing every alternate line first, flowing from the top, then every remaining line next. If I'm playing a game, I get about 1–2 frames per second. I'm not sure if it's graphics driver related, because I'm using a (dual) optimus Nvidia card with bumblebee. I see this problem in games (i.e. on the Nvidia card) or in Firefox (i.e. on the integrated Intel chip).

I've tried replacing plasma with `kbuildsycoca4 ; kquitapp plasma-desktop ; sleep 2 ; kstart plasma-desktop`, but this does not fix it. However, if I change compositing from OpenGL to XRender (with either Qt graphics system), it fixes it. (This is suboptimal in the long-term, as XRender doesn't perform all effects properly, such as blur.) Alternatively, I can restart or log out and back in. If I remain logged in (with it broken) then log into another account simultaneously, the graphics are fine.

Cheers.

This sounds like something may be causing KWin to trip up somehow - does temporarily disabling Desktop Effects using Ctrl + Alt + F12 help?
Also, can you verify that KWin is using the correct set of libraries for the graphics card it is run against?

bcooksley wrote:This sounds like something may be causing KWin to trip up somehow - does temporarily disabling Desktop Effects using Ctrl + Alt + F12 help?

I'll give this a try when it next occurs.

bcooksley wrote:Also, can you verify that KWin is using the correct set of libraries for the graphics card it is run against?

I'm not sure how to do this. However, the problem is intermittent, so I presume that it is normally okay?

Key things that could cause problems are if you use Bumblebee to switch between Nvidia / Intel during a session.
ie. Does it occur if you stay with the same graphics card and leave the other "inactive" for the entire duration of the session.

bcooksley wrote:Key things that could cause problems are if you use Bumblebee to switch between Nvidia / Intel during a session.
ie. Does it occur if you stay with the same graphics card and leave the other "inactive" for the entire duration of the session.

I'm not 100% sure what you mean. Both can be running at the same time. In that case, when the error occurs, I see it in multiple programs using both cards. I have also seen it occur when the Nvidia card has been inactive. However, in those sessions, I'm not sure if I previously had the Nvidia card running.

Okay. One other thing you might want to check is dmesg (when it is happening) to see if any messages regarding graphics hangs, memory issues, etc are being noted.

bcooksley wrote:Okay. One other thing you might want to check is dmesg (when it is happening) to see if any messages regarding graphics hangs, memory issues, etc are being noted.

Thanks. I'll check that out too when it next occurs.

Okay, it happened again. In /var/log/kern.log, I found:

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May 25 13:32:29 sparhawk-XPS-17 kernel: [13549.869879] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
May 25 13:32:29 sparhawk-XPS-17 kernel: [13549.869885] [drm] capturing error event; look for more information in /debug/dri/0/i915_error_state

There is nothing at /debug/dri/0/i915_error_state, but there is a file at /sys/kernel/debug/dri/0/i915_error_state . I've uploaded it here.

==EDIT==
Sorry, I forgot to say that turning off compositing does make the graphics more responsive. It's certainly usable, but feels slightly less responsive to what I'm used to.

I tried watching a full-HD 50-FPS video in VLC, and it failed. Audio played fine, but the video was stuck on the first frame. I tried with both OpenGL and XRender, with compositing turned both on and off (i.e. four permutations).

Okay, this indicates the Intel graphics unit it hanging, possibly for any number of reasons.
If possible, could you try disabling Bumblebee completely to ensure that only the Intel driver and card are active on the system?

The DRM Prime infrastructure which supports buffer sharing is still very new, and could possibly be triggering the issue somehow.
You could also try upgrading to a newer Intel driver - especially if you are using Ivy Bridge hardware.

bcooksley wrote:Okay, this indicates the Intel graphics unit it hanging, possibly for any number of reasons.
If possible, could you try disabling Bumblebee completely to ensure that only the Intel driver and card are active on the system?

I'm not really sure, but is this unlikely if I get these freezes when the Nvidia card is inactive?

bcooksley wrote:The DRM Prime infrastructure which supports buffer sharing is still very new, and could possibly be triggering the issue somehow.
You could also try upgrading to a newer Intel driver - especially if you are using Ivy Bridge hardware.

Could you please point me in the right direction on how to upgrade my Intel driver? (And also how do I tell if have Ivy Bridge?) I think this is worth a shot, but as mentioned earlier, I think it's a regression, so I'm not sure that immature drivers are to blame. (But who knows!)

Hi, you may want to check into http://www.kubuntuforums.net - a very helpful and knowledgeable bunch last time I was there - and distro specific

toad wrote:Hi, you may want to check into http://www.kubuntuforums.net - a very helpful and knowledgeable bunch last time I was there - and distro specific

Thanks toad. I might try them if this thread cannot help. Do you think this might be a distro-dependent problem?

Hi Sparhawk,

I have no idea to tell you the truth but it is more than likely that the xbuntus do things differently, especially with regard to X. But whether in this forum or another, good info is what people need to help you. What is the output of:

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lspci -k|grep -i -A2 vga

The process of upgrading the Intel driver usually involves upgrading various packages including Mesa and X.
Doing this is definitely a distribution specific procedure.

To determine if your machine is a Ivy Bridge, look for the model name in "/proc/cpuinfo" and perform a search for that. It should lead to a site informing you which generation your system is.

Thanks to both of you. I feel a bit odd double-posting (even if it is another forum), so let me know if this gets beyond your expertise (or too tedious) and I'll post in the kubuntu forum.

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$ lspci -k|grep -i -A2 vga
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
   Subsystem: Dell Device 0571
   Kernel driver in use: i915
--
01:00.0 VGA compatible controller: NVIDIA Corporation GF116M [GeForce GT 555M/635M] (rev ff)
03:00.0 Network controller: Intel Corporation Centrino Advanced-N 6230 [Rainbow Peak] (rev 34)
   Subsystem: Intel Corporation Centrino Advanced-N 6230 AGN


And the model is Sandy Bridge (Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz).