ADL-S struggles with RPS (GuC?), causing gnome-shell stuttering
I was really hoping this was going to be fixed by the time ADL-S came along but unfortunately so far this doesn't seem to be the case. What I've been noticing is that i915 does a really poor job of handling frequency scaling correctly.
Basically what seems to happen is that the GPU doesn't upclock quickly enough in response to there actually being GPU activity. The easiest way I can reproduce this is just by starting up a gnome-shell session on Fedora on a machine with a 4K display, and just watch the shell animations stutter. I know it's an RPS issue because if I go and force the GPU frequency to max speed with:
echo 1450 > /sys/class/drm/card0/gt_min_freq_mhz
The stuttering is completely gone and everything runs at max framerate all the time.
The other thing too is that unfortunately I also know it's RPS because this has actually been a very long running recurring issue with i915 in general. There was quite a lot of issues with stuttering previously on Skylake+ hardware:
https://bugs.freedesktop.org/show_bug.cgi?id=44006
Which on numerous occasions regressed again unfortunately, and as of right now is still definitely not working well on SKL+ (e.g. animations lag there as well). This never seemed to be an issue for me on tigerlake, but I also don't run anywhere near as many 4K screens on my tigerlake machine.
So: I'm hoping with opening this bug we can finally get a solution for this and maybe stop things from regressing. I'm happy to provide as much debugging info as needed and have plenty of systems to test.
EDIT: Almost forgot to mention the machine I'm currently seeing this on. It's a Lenovo ThinkPad P1 5th Generation with a: 00:02.0 VGA compatible controller [0300]: Intel Corporation Alder Lake-P Integrated Graphics Controller [8086:46a6] (rev 0c)
on Fedora 37 kernel version 6.0.7