Tweaking Performance in XCOM 2

When Firaxis chose to use Unreal Engine to power their latest title, XCOM 2, they chose to stay on the older version 3 of the engine instead of the latest, and fully Linux-compatible, version 4. It seems that when they brought XCOM: Enemy Unknown to the masses, they'd hacked that version 3 engine so much, it was practically an entirely new fork. Porting all their customisations to the newer engine would have been daunting, so they decided to stick with that customised engine for XCOM2.

However, this has brought some hangovers from that earlier version with it, hangovers that Feral left in place during the porting. In particular, many titles using UE3 suffer from an extremely low default memory allocation. In fact, the default PoolSize is set at just 10Mb, and I suspect that Feral have to leave it that way to ensure maximum compatibility. In fact, besides Poolsize, you can tweak quite a few settings in your game's ini file, but as usual, it appears that PoolSize is the primary factor in smoothing out the performance. Original credit to this tester for Unreal Engine 3 here from 2013, regarding the original XCOM game.

Having tried these changes myself, I can report that performance leapt from "frustrating and shoddy" to "entirely playable". There is still a little stutter evident in the loading transitions while in the dropship, but in-game performance is definitely a huge improvement. I'd go as far as to use the phrase "buttery smooth". No more slide-show explosions, or missed action-shots.

Here's what you can do.

Important Note: We suggest reverting these changes for any patches that come, as it could affect them. Always revert changes like this when a patch is released.

Before making any changes, you might want to make a copy of your file, then you'll need to open it for editing:

cd ~/.local/share/feral-interactive/XCOM2/VFS/Local/my\ games/XCOM2/XComGame/Config
cp XComEngine.ini XComEngine.ini.original
gedit XComEngine.ini


And then find the PoolSize=10 line and change it to something more reasonable, such as 256.

If you just want the quick fix, you can skip this section, however as the more detailed article points out, you might want to change the following lines too. I did, but it's not entirely clear how much they contribute. Feel free to experiment!


MipFadeInSpeed0=0
MipFadeOutSpeed0=0
MipFadeInSpeed1=0
MipFadeOutSpeed1=0
MinSmoothedFrameRate=30
MaxSmoothedFrameRate=400
bInitializeShadersOnDemand=True
DisableATITextureFilterOptimizationChecks=False
UseMinimalNVIDIADriverShaderOptimization=False
PoolSize=256 (or VideoRAM/4, up to 768 max)
bAllowMultiThreadedShaderCompile=True
ThreadedShaderCompileThreshold=4 (match your CPU cores, so an i3=2, while i5 or i7=4)
OnlyStreamInTextures=True


Having made the changes, the first thing that XCOM 2 tries to do is set it all back to default values again, so you'll need to mark that file read-only:


chattr +i XComEngine.ini


(actually, you might want to make that change with sudo so that root owns the file, preventing XCOM 2 from changing it back - some users reported that XCOM 2 does indeed "undo" the read-only flag!)

And that should be the game fixed up for immediate play!

As always, there are a lot of systems out there that will handle these changes differently, so your mileage may vary. Remember to mark the file read-only before playing and if you still don't see a change, try the "reset to defaults" trick mentioned in the original source article.

For reference, my system specs are:

O/S: Ubuntu 14.04 64bit
GPU: Nvidia GTX670, 2Gb
Chip: Intel i7 2600k
RAM: 16Gb

I used the 256Mb PoolSize as shown above, but could have gone 512Mb, as the original source article suggested "GPU memory divided by four". I used the ShaderThreshold 4 as shown above.

If you don't know your video memory, you have two options. If you're using Nvidia, you can simply run the Nvidia XServer Settings GUI (and I think Catalyst drivers might have a similar option actually). Otherwise, you can run:


dmesg | grep VRAM


That will hopefully show you how much RAM your computer detected on start up.

Good luck, Commander! Article taken from GamingOnLinux.com.