Comment # 6 on bug 1129035 from Vit Pelcak

(In reply to Stefan Dirsch from comment #3)
> Hmm. Any reasons why are you setting all these i915 kernel module options
> and use xf86-video-intel instead of modesetting X driver, which is our
> default on Kabylake? I suggest to use our defaults first ....
> 
> Other things I noticed when looking at your description.
> 
> I see that you're already using intel-media-driver as backend for libva
> (which is our default on newer platforms now instead of intel-vaapi-driver).
> Indeed performance should be better with intel-media-driver than with
> intel-vaapi-driver, but maybe it's not. It's
> rather new ...
> 
> I was wondering why vdpauinfo works on your Intel GPU system. Seems you have
> installed libvdpau_va_gl1 wrapper, which maps things from VDPAU to libVA.
> Maybe that's the issue here, if GTM tries to use VDPAU, then everything goes
> through libVA. Maybe if VDPAU would fail, it would fallback to libVA and
> then could use the direct path. But this is only a shot in the dark! I don't
> know
> anything about GTM.

Hello.

Yes, I removed intel driver. Problems stay. Actually, I initially already had
problems, therefore I tried intel driver.

When I test with some 4k 60 fps video on youtube (regardless of the browser),
then all cores are heavily loaded even while using modeset driver.

Switching screens in GNOME causes quite heavy load on system as well.

That suggests that video acceleration is not working well.