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Looking Glass - Triage



Sorry it took me a while to get back to you, I need to figure out how to get updates on the forum on my email.

It looks like that fixed the problem, I will let you know if I find any problems.

Thanks (=


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What is the expected framerate / performance for LG at 4k resolution? I’ve seen very mixed reports.

Host CPU: i9-7980xe
Host GPU: Vega 64
Guest GPU: GTX 980 ti
Guest resolution: 3840x2160 (128MB shm)
LG version: a11

In some games it works fine at 60fps (The Witness), in some it slows down in the game proper (Dota 2 down to about 33fps), and at times it seems to have trouble on the windows desktop. I’m not sure what to attribute to what at this point.


Anything > 1200p at this time is not great. A12 when released has some substantial improvements, however profiling shows that we are limited by the capture speed of the guest video card itself now.

This may be better with NVFBC, but until fixed again I don’t know for sure yet.


Hi folks,

I’m following(ish) the guide, but not sure where to continue with “Adding the IVSHMEM Virtual Device”.

I use Virt Manager on Arch to manage my VM’s locally and on remote machines. Anyone know how I would pass on:

-device ivshmem-plain,memdev=ivshmem,bus=pcie.0
-object memory-backend-file,id=ivshmem,share=on,mem-path=/dev/shm/looking-glass,size=70M

from within Virt Manager? I don’t use KVM/QEMU from command line usually.


Please follow the official guide, it shows how to do what you’re asking.


Watch out, CS:GO uses VAC and VAC now kicks you out of games if it sees you’re running a VM. It’s better to optimize CS:GO for your host OS with mouse acceleration tweaks.


The size is not a POWER OF 2.

Closest power of 2 size for the shared memory file to 70MB is 64MB. Use virsh edit to add QEMU command line entries to the XML of your VM.


DXGI has capture performance limitations. And overhead to turn buffers into RGB32 might require more GPU power, like (regrettably) a RTX 2080 Ti.

If the DXGI capture is instead capturing directly the DirectX output and not a fullscreen, some performance can be gained back.

@gnif, this is where a graphical GUI for the Windows Host application would be handy to have an option to grab only the DirectX output of the game, and not the entire screen, kind of like Game Capture in OBS, for those of us doing streaming using Looking Glass.


Anyone know of any idiot proof setup guides for Looking Glass? I am honestly surprised I even made it this far with my GPU passthrough. The Looking Glass website guide only instructs building Looking Glass from source but is there not any precompiled builds I can download somewhere?


It’s still a bit of a tech preview. the website should have general guides. If you have trouble with the guide, feel free to ask questions here and we can help.


Ok thank you. So first question I am at the point where I need to create a script with these lines in it:

touch /dev/shm/looking-glass chown user:kvm /dev/shm/looking-glass chmod 660 /dev/shm/looking-glass

But it says that I need to modify the script, what exactly do I need to modify? Is /dev/shm/looking-glass supposed to point to the build I created in the bin folder?


Mostly just permissions. You probably are fine with it as is though, if it runs into problems, you can fix them as they come.

No. It’s a shared memory file. This is the access point (on host side) of the shared memory that the VM and host can both see.


@ChuckMCCluck I moved your thread to the the Triage area. Please be sure to read the docs.

Also, read the original thread. There are curated list at the bottom for set up guides.

Thank you.


Okay ran the script as it was and I get this error:

chown: invalid user: ‘user:kvm’


Please read the set up guide that I linked to you previously.


lol, dumb shit here missed the bit in bold that “does not apply to me” thanks for pointing out the obvious!


I may be missing it but I’m not seeing anywhere in the post you linked about running the scripts and the error I am getting. But I assume that I need to modify the script and replace user:kvm with my username?


Both with your username if you want to have the shared memory file be owned by your user and group, with a modification to qemu.conf to make QEMU run with your user and your group.

That’s at least how I got around it.


Hi All. Experiencing low UPS numbers in games like Rocket League, Starcraft 2, and PlayerUnknown’s battlegrounds @ 1080P resolution 60hz. They all to run at 60 UPS or below. With 60 almost seeming like a software cap it does not want to pass.


  • Counter-Strike Global Offensive also caps out @ 60 UPS
  • Bit Trip Runner 3 caps out @ 60 UPS (should be easy to run)

These games seem to cap out at around 60 UPS. They run fine on the connected monitor, and the games themselves are all running @ 100+ FPS. KVM Looking glass client reports ~200 fps output as well.

I tested out a very low intensity game called “Teeworlds” and got ~180 UPS and 200 FPS.

Am I having issues or is ~57-60 UPS expected performance on modern games for looking glass @ 1080p with my specs.

PC Specs:
MSI-Z270A Pro Motherboard
Guest has 4 cores (1 socket, 4 cores, 1 thread each)
32GB (8x4) of DDR4-2400
Host: AMD RX580 8GB (AMDGPU) (PCI-E 3 @ 4x)
Guest: GTX 1070 (PCI-E 3 @ 16x)