https://bugs.kde.org/show_bug.cgi?id=452119
Nate Graham <n...@kde.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|Poor performance on wayland |With an Intel iGPU,
|versus Xorg |animations aren't as smooth
| |on Wayland versus Xorg
Severity|major |minor
Version Fixed In| |5.27
--- Comment #52 from Nate Graham <n...@kde.org> ---
We're getting reports from Intel iGPU users that the Wayland session is and
smoother with that change in Plasma 5.27. And this is my experience as well!
I was feeling curious so I decided to do some investigation and measuring. From
what I can tell using intel_gpu_top, here's what's going on with my Intel HD
620 GPU:
On both X11 and Wayland, the GPU's clock speed is always below 20 MHz at idle
(and frequently 0MHz), which mean the GPU is idling. In this state it reports
using about 1.3 watts of power.
On X11, when I open the Overview Effect with Meta+W, the GPU immediately comes
out of idle and the clock speed jumps to 300+ MHz. The animation is always
smooth.
On Wayland, when I do this the GPU comes out of idle and the clock speed jumps
to 600+ MHz, and even when using the new default setting of "Force smoothest
animations", it's not quite as smooth as on X11. Sometimes it's close,
sometimes it's less close. It's better than it was before, but still not
quiiiiite as good as on X11.
When I turn on the Show FPS effect, an animation is constantly played and
minimum GPU clock speed jumps to about 80 MHz. The power consumption is
slightly higher at about 1.55 watts. The GPU now constantly has work to do and
doesn't idle anymore; in this state, newly-played animations are as smooth as
on X11.
So it seems like there is a difference on X11 vs Wayland regarding how the GPU
handles coming out of an idle state. On X11 it does this quickly enough that a
newly requested animation is smooth. On Wayland, that's not the case, and to
replicate the same results, you have to force it to not go idle. The cost in
power consumption to do so is small, but measurable. And on a laptop, it would
be impactful.
I don't have enough information to speculate about whether this is a GPU driver
bug, and/or if it's something KWin can do better about.
Regardless, the differences between X11 and Wayland in smoothness are now much
smaller than they were before, even if we're not 100% of the way there I'm
removing this bug from https://community.kde.org/Plasma/Wayland_Showstoppers
since such a small difference in performance is not a showstopper.
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