Several of my players reported this. I just updated to the 1903 windows release to test and can confirm the issue.
Anyone else noticing this?
This is a brutal performance drop!
That is brutal. I’m on 1803, and now I don’t want to update again. Windows 10 updates have consistently broken just about everything in my workflow, including one update causing the UE3 editor to crash every time it saved a package.
You can cross your fingers and hope that a future Windows 10 update will fix this soon. There’s probably not much you can do to improve performance on your own… unless you had access to the underlying C++. 
Probably the best way to approach it would be to run your game with the Gameplay Profiler, then roll back the update, and run your game with the profiler again, and see where the performance hit happens. I think all of us would be very interested in seeing what the issue is.
Do you have any other UE3 or UDK-based games that took a performance hit?
Edit: I’ve been going over What's new in Windows 10, version 1903 - What's new in Windows | Microsoft Docs and it mostly reads like marketing copy. It’s all “this is the new stuff Windows does better,” and nothing about “we changed the way this works for greater security (or whatever), but it means that all your code is going to run slower.” Does anything in there stand out to you?
It looks like there are reports on other UE3 games on the Steam forums. On the Toxikk forums the devs state they’ve found the issue and are rolling out a fix: https://steamcommunity.com/app/32481…69167147580118
I was wondering why so many of my players were reporting performance drops, then this morning i updated to 1903 and my fps dropped significantly.
So did he reach out to you explaining the fix?
I suspect Microsoft did something to windows defender and that machine learning., do you have windows defender activated?
Looking at google Battlefield 5 is down too.
I just checked out the TOXIKK forum. Looks like they had to write a new dll. Do you know if they had to change the way UE3 accesses a dll? Or did they have to change the way something in the dll works?
Oh no, you mean it gets even worse?
I already had huge startup times if Windows Defender was on, because Windows scans my game’s exe for malware even if it’s whitelisted, I always thought that might have something to do with the dllbind I use.
As far as I know, the slowdown is being cased by Stats being enabled in the compiled UDK exe (#define STATS) and the code that collects the memory usage is causing a big slowdown on Windows 1903.
In the c++ it is this line causing the issue: GMalloc->GetAllocationInfo( MemStats );
It’s possible to cancel out this call in the UDK.exe by replacing the bytes with 0x90 (NOP) instructions.
Here is a patched exe for the UDK-2014-08 build: UDK-exe-windows-1903-fixed.zip - Google Drive
This means when using this exe, you may be missing some profiling data, so keep the old exe around for troubleshooting and use this one for your release build. Unzip with 7zip, otherwise winrar/winzip stamp the file as downloaded from the internet and will prompt players with an “Unkown Publisher” warning when running the exe for the first time.
Props to modder PredatH0r for finding this.
If you remove the stat.dll from the binaries folder. Will that stop this problem?
We forgot it in an upload one time and the game ran fine. It just would not update the online steam achievements.
Does the patched exe allow achievements to work properly then?
Also, could I please get some tips on how to patch the exe for the July 2013 version of UDK?
I also want to know about the 2013-07 version as its what i use, if can fix it up for us for 32 and 64bit wink wink .Of course when you have the time mate 
.Or maybe even a step by step tutorial so that we dont have to bother you like kids.
Also, does anyone knows if this is just dx9 related? DX 11 maybe fixing it?
Im on 1709 as its stable just like the 1800s and don’t have the ability to test on 1903.
Predath0r from Toxikk’s Discord (chat.toxikk.com) was able to provide a ToxikkBind.dll for the game dev’s to work with. Win10 users with 1903 are reporting a complete FPS fix with the recent update of Toxikk v1.2 - Feel free to reach out to Toxikk’s game Dev’s or Predath0r in discord for the fix if you’re a developer.
As far as I understand, UDK’s engine was polling dead space creating fps spikes / lag etc. I’m no expert on the subject, but from my own experience my game experience has improved greatly.
Win7 64bit - Toxikk v1.2
My FPS is capped at 70FPS normally (GTX 750Ti, pos old system), my in-game frame time ms has dropped from 20-24ms down to 14-15ms since the update in Toxikk.
From what i understand is that the 1903 windows doesnt accept older gpu drivers and the fix was in the latest gpu drivers.For nvidia is 431.36
https://social.msdn.microsoft.com/Forums/en-US/0ca2d5c3-7957-4706-89d5-556e207ba9fc/windows-1903-update-causing-big-performance-drop-for-unreal-engine-3-game?forum=windowsgeneraldevelopmentissues
Also people speak that windows update KB4505903 shoud fix this too.Anyone managed to try that to confirm?
I can confirm that when I checked today with the latest Win10 1903 updates and nvidia driver 431.36 installed, the frame rate problem was gone and the self-made patch for TOXIKK/UDK is no longer required.
(It had nothing to do with Windows Defender or DLL-Binds… the slow-down affected my installations with Windows Defender and Kaspersky AV equally. Also it seems that the 64bit udk.exe was not affected by the slow-down. DX9 or DX11 didn’t matter)
Edit:didnt noticed that Predath0r posted before me :o
A small update.I just talked on discord with Predath0r(a really cool person by the way) and looks like nvidias new drivers or the latest windows update KB4505903 do fix this issue.As he tested the UE3 game TOXIKK with and without the patch but with newest drivers and now things look the way as they should.He is not sure if its the nvidia drivers or the windows update but one of the 2 fixed the thing.He also mentioned that with his patch 2 users with low end pcs experienced slightly better fps in the menu of the game 220 without patch and 230 with patch but with the patch they do have significantly more stable frame times with less micro-freezes so the problem is probably still not ironed out perfectly.
Good news is that by his observation the udk 64bit exe builds don’t seem to be affected by the 1903 upgrade.
I have no idea if the amd gpus were affected by the 1903.
It would be really cool when Cold Scooter has the time, to tell us his observation of the situation first hand if the gpu drivers fixed the thing in his environment 
Have same issue on AMD Radeon rx570. Resolved by updating Windows 10 to 1910 Now fps constant hi and do not drop.
Thank you for that info.Really helpful as i haven’t been able to find someone with a amd gpu to confirm it.Glad its back to normal, really glad 
Yes, me to I experienced something like that.
Fixed after the win update or gpu drivers I hope,right?