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Re: [kde] kwin (4.11.12) idle CPU usage




On 27/01/16 03:40, René J.V. Bertin wrote:
On Tuesday January 26 2016 17:20:38 Duncan wrote:

more flashing you see and the bigger area that's flashing, the more
repainting is being done and the higher both kwin_x11 and X's usage
should be.
Maybe, but *why*? Kwin isn't supposed to do anything with window contents in my configuration, when I'm not interacting with the system.

Given that he said quitting Chrome dramatically reduced kwin's CPU usage,
I'd guess that with this effect enabled, Chrome will be flashing like
crazy.
It isn't. The whole window rect is indeed flashing whenever a tab is active, but nothing happens when that is not the case. According to chrome's own task manager only the central browser process is active when the browser really ought to be idle (around 10% of whatever) plus around 2% for the GPU task. I can kill the GPU task (only effect is it'll restart and stay at 0%) but not the central process.
I recall having seen what appeared to be tiny offscreen windows looking at an xwininfo dump recently, maybe those are the culprit. I'd hope kwin would be clever enough not to attempt to composite anything with invisible windows though.


I think I have seen what you are describing on my system. When I turned on paint, the whole chrome tab was refreshing constantly (indicated by the cycling colours across the whole of chrome, including the menu), with significant CPU time for kwin_x11. The refreshing happened independent of it being in focus or not. Then I started google-chrome-stable to see if the stable version has the same problem and without changing anything in the running google-chrome-unstable, I don't see that problem any more. I did open some menus in google-chrome-unstable and that seem to have "fixed" the issue temporarily.

So it almost looks like that chrome can get into a state where it constantly refreshes the whole window and then is causing load through the kwin_x11. I can confirm that chrome itself was fairly idle. At least in my case it was temporary. But I certainly saw a similar effect. I will keep an eye out how often that happens...

Gerald

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