KWin Compositing GPU usage - Running hot while idling

[Guest]

I am replicating my post from http://forum.kde.org/viewtopic.php?f=111&t=95330 here, seeing as the userbases have some overlap and probably also the expertise.

KWin runs my GPU hot even while doing little or nothing. Simply enabling compositing is often enough to bring the GPU up to 65 degrees Celcius. Minor use of fairly load-friendly functions like minimizing or using the alt+tab switcher guarantees it. This may seem trivial, but the constant, high-pitched squeal of the cooling fan renders enabled compositing a fairly unbearable experience (I find compositing very useful in and of itself). Hopefully, the information below will explain why I suspect it's a bug with KWin when using NVidia binary drivers.

Short hardware/system info (more details at end of post):

Graphics card: NVidia GeForce G105M 512mb
Distribution: Kubuntu 11.04
(current) KDE version: 4.6.2 (seemingly irrelevant)

Time/persistence: This problem has been with me since KDE 4.4.2, very probably even before that (it's been a while, I lose track), but at least for a year now, in every version and update I've tried for the past 12 months.

What I've tried:

1) Changing NVidia binary driver versions. I've gone through just about every version from the currently newest to as far back from NVidia's archives as my kernel would successfully support. Please note: I can not use, or even test, the nouveau drivers on this, because they frequently freeze my system completely shortly after loading (and seem to have done so for a few versions). As I do some gaming and need the performance and stability of the binary drivers, nouveau is unfortunately not an alternative for me.

2) Reinstalling the OS from scratch, taking no settings with me from the old installation. I have done this over several versions of Kubuntu/KDE, also.

3) Starting KWin with both 'KWIN_NVIDIA_HACK=0 kwin --replace' and 'KWIN_NVIDIA_HACK=1 kwin --replace', ie. explicitly enabled and explicitly disabled. Not sure if that hack even does anything any more, but it was worth a try.

4) Tweaking settings left and right in the NVidia control panel.

5) Disabling one effect after the other in system settings, restarting kwin after each change, while keeping compositing active.

This is not:

1) CPU usage. NVidia control panel shows the GPU jumping to ~65C on very simple operations while 'sudo top' shows Xorg and kwin using 1-2% CPU, and at that, they are the heaviest loaders. 'acpi -t' furthermore shows no noticable increase in CPU temperature (1-2 degrees Celcius, tops)

2) Dust accumulation on the heatsink. The problem came literally overnight, after a system upgrade. Furthermore, this is a laptop, so the CPU and GPU share the fan and heatsink, but the CPU's response to load is the same as it has always been.

3) Specific to some particular desktop effect, driver version, KDE version, or driver/KDE misconfiguration. I say this with fair confidence, considering the list of things I've tried so far.

I recall things working just fine in Kubuntu 9.04, which used KDE 4.2.2, so it seems clear that the problem has emerged sometime after KDE 4.2.2 and remained since.

So my question is simply this: Can anyone tell me what's going, how I can fix this, or how I can find the cause?

Some more system information follows, replicating a few bits for your reading convenience.

Laptop make/model: Acer Aspire 5738ZG
Graphics card: NVidia GeForce G105M 512mb
Driver version: NVidia official binary driver 270.41.6
CPU: Intel Pentium T4200 2Ghz Dual-Core
RAM: 4gb DDR3, not shared with the graphics card

KDE version: 4.6.2 (this probably isn't relevant, as the problem has been with me for several versions now.)

* Output from 'kwin --replace':

OpenGL vendor string: NVIDIA Corporation
OpenGL renderer string: GeForce G 105M/PCI/SSE2
OpenGL version string: 3.3.0 NVIDIA 270.41.06
OpenGL shading language version string: 3.30 NVIDIA via Cg compiler
Driver: NVIDIA
Driver version: 270.41.6
GPU class: G80/G90
OpenGL version: 3.3
GLSL version: 3.30
X server version: 1.10.1
Linux kernel version: 2.6.38
Direct rendering: yes
Requires strict binding: no
GLSL shaders: yes
Texture NPOT support: yes

[dibl]

Re: KWin Compositing GPU usage - Running hot while idling

I don't know that GPU. A quick check on Nvidia's forums indicates there are other folks with that Acer laptop having thermal problems with it.

It sounds like you're a KDE user, but have you done any experiments with other DEs? I've got a suspicion that it's a flaw in the driver itself, which probably means that Gnome or Xfce would not be dramatically better in terms of heating it up. But it would be interesting to find out whether the problem is on any Linux DE, or is limited to KDE. Probably you could work with a Live CD and figure out whether it is behaving the same, or differently.

[Guest]

Re: KWin Compositing GPU usage - Running hot while idling

I don't know that GPU. A quick check on Nvidia's forums indicates there are other folks with that Acer laptop having thermal problems with it.

It sounds like you're a KDE user, but have you done any experiments with other DEs? I've got a suspicion that it's a flaw in the driver itself, which probably means that Gnome or Xfce would not be dramatically better in terms of heating it up. But it would be interesting to find out whether the problem is on any Linux DE, or is limited to KDE. Probably you could work with a Live CD and figure out whether it is behaving the same, or differently.

Thanks for the tip, I gave the NVidia forums a look. While it does seem that some do have thermal problems with this GPU, all I could see was 1) questions of whether some non-critical, but elevated temperatures were normal while running games and 2) reports of over-heating and shut down. The former seemed perfectly normal to me, and the latter is unfortunately a problem many report without paying proper attention to ambient temperature, the surface the laptop is resting on, and just how much dust they've exposed it to. All I can say on that matter, therefore, is that during the ~2 years I've had this laptop, I've never had overheating problems. Sure, that one time when I was maxing out Left 4 Dead 2 (in Windows), completely forgetting that the laptop was sitting atop a blanket, the whole thing shut down, as it should, but it came as no surprise with a blocked air-intake, and putting it on a flat surface eliminated that little snag completely. That was the only time I've had an overheat, and save for the subject of this thread, I've never had any abnormal behaviour in the Windows Vista installation that came with the laptop, or in Kubuntu, or in any of the 10+ games (with at least 6 different engines) I've been running in Windows and sometimes (the norm lately, actually) Wine.

You are correct, I am a long-time KDE user I haven't experimented with other DEs, but I'll give that a go tomorrow (when I have the time to poke around a bit). I, too, suspect that the drivers hold a large share of the blame, but as far as I can recall, the issue occurred after an upgrade to KDE with the driver remaining the same, so it seems to me that the blame perhaps is shared between kwin and nvidia-drivers - some improper interplay of the two.

While I have tested all possible versions of the NVidia drivers I could get my hands on for Kubuntu 10.04 (just upgraded to 11.04, and given the results in 10.04, it seems pointless to go over the same procedure with the drivers in 11.04), it just occurred to me that I have not tried eg. 9.04 with the most current drivers, or at least later versions than the one I was running when 9.04 was installed.

I will try some other DEs, and current versions of the nvidia binary drivers with Kubuntu 9.04, tomorrow, and post my results when I'm done.

Anyway, thanks for the help so far.