VRAM Usage Drops After DCS Window Goes Out of Focus

[markbam]

I'm a Quest 2 user and have been running into DCS performance issues that I believe are related to the low VRAM of my 3080. Using a plugin for MSI Afterburner, I have been monitoring VRAM *usage* (*NOT allocation*) specifically for DCS.

 

I have come across a strange occurrence that is always repeatable and gives credence to the accounts I've read of people switching windows and performance improving.

 

Whenever the DCS window goes out of focus, a good chunk of VRAM is freed. However, this only happens once per aircraft spawn. Something about the initial aircraft load adds a bunch of data to the VRAM that does not usually get cleared. But, for some reason, clicking a different non-DCS window causes DCS to run a garbage collection(or something), thereby freeing up precious VRAM.

 

Please reference the included graph:

 

You will see that I load DCS; load into a multiplayer server (in this case Syria@War); then load into an F14. (VRAM usage goes up as expected)

I let DCS sit for a bit, then click away from DCS to the Task Manager in order to shift it out of focus. (You will see zero VRAM usage because afterburner is now polling the usage of the new active window: Task Manager)

When I click back to DCS, a portion of VRAM is cleared.

I click away again a few times, and the VRAM usage now stays the same.

I now respawn into another aircraft. (You are able to follow the increasing VRAM usage each time I do this)

I repeat the same process again on multiple aircraft with the same results.

 

Not sure what this means in the grand scheme; perhaps this is a bug and DCS has room for a VRAM optimization step. At the very least, maybe this information could help someone in my position who is trying to diagnose performance issues related to their VRAM usage.

(Side note: I have to run Textures- Medium and Terrain Textures- Low in order to not saturate my 3080's 10Gb VRAM on Syria.)

 

Update: I have received the same results utilizing 2D mode, OculusAPI VR, and SteamVR. This happens in both single player and multiplayer.

I have also noticed that subsequent switches to different aircraft(without changing window focus) will increasingly grow the VRAM usage.

However, the game will quickly stutter and garbage collection does appear to happen when the VRAM completely fills up in this way.

 

My Specs:

i9-11900K @ 5.4ghz on water

64GB RAM @ 3600mhz

GeForce RTX 3080 FE

2TB NVMe

Quest 2: Wired Link 5408x2736@90hz

 

Edited July 25, 2021 by markbam

[silverdevil]

interesting research. i do not have any empirical data as you have. however, i do hear the fans spin up and down in similar spots while running DCS.

[Lemming]

I registered on these forums to try and get some idea of what is going on with all this. This seems to be a very common problem that many people are having issues with, the problem is that everyone explains it a little diffrent because it's quite hard to understand what is really going on.

After having read many diffrent threads, and other websites, I am starting to suspect there is a "conflict" of sorts between various softwares.

One of the things I've noticed is that FPSVR which is a great program for seeing VR performance, amplifies this problem major, resulting for me in like 1-2fps with overlay on, and 45 fps with it off....

I think part of the problem is that VR got off to a bit of a bad start software wise, as there are so many various technologies and systems suppose to work together. 
Like for me having to run WMR via SteamVR to make DCS work. And there are multiple duplicate settings that basicly do the same thing just in a slightly diffrent way.

I am hoping that manufactures of VR can all get behind a singel API and stick with it. Like I think I read that Oculus will move to openXR, so then we can hope that WMR will follow, and that this will also make it easier for developers.