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AMD AM4 platform poor OpenGL performance if IOMMU grouping is borked
chancho_zombie commented on 24 July 2019 at 2:02 am UTC

Hi everyone.
Recently I had problems with HITMAN and Life is Strange, constant freezes, I just discovered that if I pass iommu=soft to grub, the bug is gone. I've been so much into vulkan gaming that I completely overlooked this, it happens only in OpenGL games. The problem is with some AM4 motherboards that have IOMMU broken, mostly the b350 but there are others.

you can check if you have this problem with this command

dmesg | grep AMD-Vi

if you read something about loop timed out or IO_PAGE_FAULT, then you probably have this problem.

entropie commented on 12 August 2019 at 12:34 pm UTC

I once read some time ago that AMD is not putting any more efforts into OpenGL development. If that means they will continue overperforming on Vulkan then, I am fine with that.
But as a rule of thumb having bad fps in openGl on AMD or other strange errors is to be expected.

MrNilsson commented on 12 August 2019 at 4:55 pm UTC

Mine looks like this:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX="amd_iommu=on iommu=pt"


iommu=pt is using the passthrough mode and iommu=soft is using the software mode. You're only supposed to use one or the other, so don't put both in your grub file.

iwantlinuxgames commented on 12 August 2019 at 6:15 pm UTC

the Asrock Phantom Gaming 6 X399 motherboard also has this issue :/

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