[PC] SLI Performance Issues

Okay, this is going to be a big one. It's also going to be extremely specific and technical, so I don't expect it to be solved any time soon, but I'm posting it here nonetheless (in the hopes that it'll be solved some day... before I build my next PC).

I'm experiencing a really strange performance problem while using SLI in this game. For starters, I'm running

• CPU: Intel Core-i7 3770K
• GPU: EVGA GTX 680 2GB (3x SLI)
• OS: Windows 10

at 2560x1440 and low textures. My drivers are also updated to 364.51. I understand this is pushing the very limits of my VRAM. I do get huge FPS drops in very specific situations where VRAM is being swapped to disk, but that is a separate issue from what I'm about to talk about. I also close every other application when I run the game, so there's nothing else to take up memory. Origin ingame is also disabled.

The strange thing that happens is, after alt-tabbing, or opening my in-game phone, and sometimes seemingly for no reason at all, performance will suddenly dip from 60-70 FPS down to 30-40 FPS. And it stays that way until I either alt-tab again, or a certain amount of time passes.

I decided to take a look at my GPU utilization, and found out that this was happening:

http://i.imgur.com/SdqiDSK.png

As you can see, after opening the map, performance drops on my 3rd GPU. I suspect this has something to do with paging VRAM out to system memory or disk (there is a noticable lag when opening the phone/map), but I have no idea why it stays that way after.

I then proceeded to alt-tab in and out of the game a bunch of times, and this is what I got:

http://i.imgur.com/Um83neO.png

It has a seemingly random effect on my GPU utilization. Sometimes I can do it to restore performance, other times it has no effect.

I played the game for a while and noticed that after some time, I wasn't getting full performance, so I looked at the graphs:

http://i.imgur.com/BOy7IgX.png

This one was really strange, and I kept driving around to see if I could figure it out. The only conclusion I can make is that it typically happens when I drive into different areas of the map, or turn the camera to face a particular section of the map. The only problem is that it's never consistent! The most consistent area that causes my performance to dip is the cutscene that plays when I exit my garage. Most of the time it'll give me just 20 FPS, but sometimes I get 40 FPS, and other times I get a full 60-70 FPS!

Now, the biggest suspect to all of these issues is the fact that I clearly don't have enough video memory, and to address that, I tried playing the game at 1600x900.

http://i.imgur.com/2X7oToa.png

It's more difficult to see, but the exact same problem is happening, even at this resolution. That doesn't instantly mean that VRAM isn't an issue, but it seems to be fairly unlikely.

Finally, the last thing I suspect that could be causing the issue is Windows 10 itself, or an interaction with it and the drivers. This could very well be an issue with the way Windows 10 swaps video memory to system memory. So I tried running the game on Windows 7 (with 364.51), and this time, the periods of low system performance went away. Instead, since Windows 7 only swaps to disk (afaik), I just got a bunch of really abrupt stutters every now and then. The reason why I figured Windows 10 might be an issue is because I experienced a similar effect in BF4 after switching to Windows 10, but it happens much more rarely. This possibly means it could be a much bigger problem between nVIDIA's drivers and Windows 10 itself.

So what does this all mean? Basically, to sum things up:

• Performance dips on individual GPUs for long periods of time.
• It typically happens after opening the phone/map, alt-tabbing, crossing certain parts of the map, or totalling my car.
• It could VRAM related.
• It happens no matter what my resolution is (at least down to 1600x900).
• It only happens in Windows 10.

I realize this a hugely technical issue that most likely needs work within the game engine or with nVIDIA and possibly Microsoft. Also I'm pretty sure probably less than 0.01% of the userbase has this problem. However, I'm almost certain that this problem can be fixed and the game can be run at 1440p with 2 GB of VRAM. For now, please don't tell me to run the game on a lower resolution. I already know that. That is not the solution to this problem. I hope somebody in the team with the appropriate skill set can tackle this problem one day.