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Varying performance issues with Vega 56 AMDGPU

I have noticed that my Vega 56 performance has been inconsistent. It seemed to work fine on install, then after a bit, stopped performing well. I mainly work on this computer so it has not been a crippling error but I would prefer everything working properly.

I have kept track over the last few major updates with the Heaven benchmark.

Kernel 4.20.6 Score: 299
Kernel 4.20.10 Score: 1925
Kernel 4.20.12 Score: 297

I am using the AMDGPU kernel driver not the PRO version.

Any help or suggestions would be appreciated.

Re: Varying performance issues with Vega 56 AMDGPU

Reply #1 –
It's probably some weird upstream kernel regression. I can vaguely recall some phoronix benchmarks in the past noting some variable performance across kernel versions in AMDGPU. The easiest thing you can do it just wait for 5.0 and hope that all works out. If it doesn't, you may want to consider grabbing the latest kernel, seeing if you still have issues on that, and possibly complaining to kernel devs.

Re: Varying performance issues with Vega 56 AMDGPU

Reply #2 –
What @Dudemanguy said. AMDGPU is in active development and changing with every minor kernel update. Once you hit a kernel version that works well with amdgpu, I suggest you stick to it until it stabilizes - kernel updates are rarely of any real benefit anyway, unless some CVE is to be patched. If you're on desktop, you can also try one of the BFS/CK kernels (linux-ck/pf); they're really fabulously responsive and lag-free.

Re: Varying performance issues with Vega 56 AMDGPU

Reply #3 –
Quote from: nous – on
What @Dudemanguy said. AMDGPU is in active development and changing with every minor kernel update. Once you hit a kernel version that works well with amdgpu, I suggest you stick to it until it stabilizes - kernel updates are rarely of any real benefit anyway, unless some CVE is to be patched. If you're on desktop, you can also try one of the BFS/CK kernels (linux-ck/pf); they're really fabulously responsive and lag-free.

I have never heard of BFS/CK, how would I go about installing and trying one on Artix?

Is there a simple way to regress back to the 4.20.10 kernel that seemed to be working well, or, better yet, skip ahead to a newer kernel?

Edit:

I have installed the linux-zen kernel with no success, and also tried downgrading my kernel to 4.20.10 using the pacman cache. No luck. My guess is it is some other obscure issue like mesa version or some side package. I believe my next step is to install fresh on another drive and see if that makes a difference.

Re: Varying performance issues with Vega 56 AMDGPU

Reply #4 –
If the issue doesn't lie with the kernel, then you should check whether xf86-video-amdgpu or mesa or any other OpenGL-related package was upgraded after kernel 4.20.10 and revert.

Re: Varying performance issues with Vega 56 AMDGPU

Reply #5 –
So after a second install of Artix, and fresh installs of Manjaro and Ubuntu the problem remains the same. The frames seem artificially  capped. I was talking with a friend of mine with Linux on his gaming laptop and he said he ran into a similar issue due to fan control. Apparently the fans never move past idle speed and the GPU has to thermal throttle. That would explain why, no matter the resolution, performance is locked at a terrible ~8-20 fps.

So the next step is to try to find good gpu/cpu fan control utilities and monitors. Is conky still a thing? I would appreciate any recommendations.

To clarify, my computer is the Acer Predator Helios 500 Ryzen edition. It has a desktop AMD 2700 and desktop Vega 56 in it. Sort of an odd duck.

Thanks again for everyone's time.

Re: Varying performance issues with Vega 56 AMDGPU

Reply #6 –
I may discovered a reason for the performance degredation. My Acer laptop is ALWAYS showing unplugged. I have attached an image. Is there any way to fix this? Is there any way to force perfomance mode on battery or disable cord detection?

Thanks again.

Re: Varying performance issues with Vega 56 AMDGPU

Reply #7 –
Does your charger cable have a pin in the middle, like Dell laptops? If so, then that's your source of problems, it's used to signal the laptop about the charger's wattage with a special semiconductor at the charger's end. Some times the semiconductor dies or misbehaves, which leaves the BIOS thinking it's underpowered and in turn downclocks the CPU.
With some laptops (not all) it may be possible to override detection by appending processor.ignore_ppc=1 to the kernel command line (edit GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub to make it permanent).
Or perhaps there's a BIOS option to control CPU frequency when plugged or unplugged in your laptop?
 

Re: Varying performance issues with Vega 56 AMDGPU

Reply #8 –
Thank you nous for the suggestion!

Once I added that kernel parameter  and rebooted the Heaven benchmark ran perfectly for about 30 seconds.
After that I saw a battery charge notification pop-up and then performance went to garbage. So it's definitely power-cord related.
My AC adapter does have the center pin and since I am not sure what to do about that detection I have just uninstalled the xfce power manager and kept the kernel parameter and all seems stable now.  I should also note that I updated upower to upower-git, which DID help with the detection but it did not stick for some reason. Once the battery reached full charge it seemed to stopped sensing the cable connection.

What a crazy ride.

Thanks for everyone's support! I can now fully enjoy my Helios 500 in Linux!