More VRAM helps a lot with DCS VR performance

[RealDCSpilot]

I suspected DCS's VRAM usage for a while now for causing occasional framerate drops and stutters, especially in MP when switching aircrafts. Typical scenario was: entering the server, choosing an aircraft, play a while, choose another aircraft (F14 on carrier for instance) and bamm! VRAM overflow - huge FPS drop. Got my 3090 (24GB) today and this problem is gone. My good old 2080ti with 11GB wasn't enough. Rule of thumb, the higher the panel resolution and/or SS setting, the more VRAM you need on top of textures and geometry filling your VRAM already.

Steam VR beta just updated and adapted to this: "Maximum automatic render resolution limit is now calculated based on gpu dedicated memory; it was previously hardcoded to 1.5x the headset driver recommended resolution. This should have little to no impact on existing headset and video card combinations, but will scale better as displays become higher res and gpus more powerful."

Edited October 2, 2020 by Alec Delorean

[Taz1004]

I suspected DCS's VRAM usage for a while now for causing occasional framerate drops and stutters, especially in MP when switching aircrafts. Typical scenario was: entering the server, choosing an aircraft, play a while, choose another aircraft (F14 on carrier for instance) and bamm! VRAM overflow - huge FPS drop. Got my 3090 (24GB) today and this problem is gone. My good old 2080ti with 11GB wasn't enough. Rule of thumb, the higher the panel resolution and/or SS setting, the more VRAM you need on top of textures and geometry filling your VRAM already.

Steam VR beta just updated and adapted to this: "Maximum automatic render resolution limit is now calculated based on gpu dedicated memory; it was previously hardcoded to 1.5x the headset driver recommended resolution. This should have little to no impact on existing headset and video card combinations, but will scale better as displays become higher res and gpus more powerful."

 

That's actually a sad reality. DCS should not be eating up that much VRAM. Stutter after switching aircrafts suggests memory leak. DCS is not releasing the resource it already used. And more VRAM will of course help but that shouldn't be.

 

That's like you suddenly get a really bad fuel mileage on your car. And you fix it by getting bigger fuel tank.

[Supmua]

But the car now goes faster and smoother. Waiting for a new dealership’s upgraded part which may never arrive won’t help the current situation. Sometimes you can’t have it both ways.

 

Anyway, does that mean the 3080 with even less VRAM might not be a good idea for DCS?

[Taz1004]

But the car now goes faster and smoother. Waiting for a new dealership’s upgraded part which may never arrive won’t help the current situation. Sometimes you can’t have it both ways.

 

Anyway, does that mean the 3080 with even less VRAM might not be a good idea for DCS?

 

Why I said it's a sad reality.

[Gunnars Driver]

Anyway, does that mean the 3080 with even less VRAM might not be a good idea for DCS?

 

Thats one of the reasons, but not the only, which made me choose 3090 over the 3080.

[speed-of-heat]

Simple reality, dcs in 2d uses half (5gb) the vram as it does in 3d (9-10.8 gb), on my kit below, I did some basic numbers using the new after burner, and you can see it Maloc / Free ING the vram, whilst a memory leak may be present, I don't think that's the problem the op is seeing. I think it's as simple as we are driving over twice the the pixels...

 

It's also the reason I went the 3090 route.

[Fri13]

This problem was already known, and noticed by those who switch aircrafts or even restarts in even single player. 8-11GB limit comes very quickly as bottleneck.

 

The obvious sign for this that DCS doesn't release memory is that after Quit Mission > Fly Again leads to aircrafts have previous settings, or map have previous mission graphics settings. Example you start at 20:15 and fly 30 min to sunset and then quit and refly, the map that gets loaded can look as dark as it was when ending mission.

 

It happens to me often that if I get damaged, then respawning without crashing first and waiting a moment, the spawned aircraft has the damage effects applied to it in spawn. Example other engine can be out, hydraulics are like gone by feeling etc.

 

Few days ago I was testing a Harrier by making quick mission and flying against 4x MiG-19P at high skill setting.

 

Each start dropped framerates, after 4-5th RESTARTS (not respawns) it was unplayable. Framerates were at 15-20 or so, ASW was all over the places.

 

I have found that simple quitting the mission to main menu is not enough, as of you got "Fly Again" the previous day's is not purged. But click first "back" and then select mission again to fly out, the problem goes away.

 

The DCS can't handle the missions and gone data. It just doesn't purge irrelevant textures, graphics and models from memory.

 

And worse thing is that those can be mixed with what is suppose be a fresh data, like respawning, mission restart or simple units spawning and deletion in succession.

 

So for some reason the is data is hold in memory and rendered at background or ran.

Eventually one might need to sometimes shotdown DCS and restart it and it is faster than waiting minutes in main menu (the 3D model at background) while data is purged. It can be seen that even that many stutter and then suddenly it becomes perfectly fine again and all work done until it builds up again.

 

And this has been a case for 2-3 years now, multiple reinstalls, multiple computers etc.

[RealDCSpilot]

Yep, DCS does not clean up VRAM properly, makes it look like a memory leak. If VRAM is full, your system starts to cache the rest to the harddisk, that additional data transfer activity adds load to the CPU and GPU and kills frametimes. That's no problem for normal single screen usage, i doubt that you can fill up 11GB while playing flat. But VR turns it all around, we are driving it to the extreme with VR. For 2 highres panels and AA + post pro effects, you need larger buffers in VRAM plus enough space for geometry and highres textures.

Edited October 2, 2020 by Alec Delorean

[The_Nephilim]

Yep, DCS does not clean up VRAM properly, makes it look like a memory leak. If VRAM is full, your system starts to cache the rest to the harddisk, that additional data transfer activity adds load to the CPU and GPU and kills frametimes. That's no problem for normal single screen usage, i doubt that you can fill up 11GB while playing flat. But VR turns it all around, we are driving it to the extreme with VR. For 2 highres panels and AA + post pro effects, you need larger buffers in VRAM plus enough space for geometry and highres textures.

 

 

Are you sure you are not meaning RAM and not VRam? I loaded up a mission in MP Played there for an hour switching planes a few times and did not notice the VRam being overused.

 

In fact when I switched to the A10C the VRam dropped by .1 or .2.. I seen the Ram go pretty high upto like 20GB.

 

I think that was also the amount of ram I had when the mission first Started so I did not see an increase in either VRAM or RAM?

 

Now the server was empty but it was still an active MP server.. So I am unsure what the OP is seeing here.. I did not get major stutters or really any that I really noticed..

[RealDCSpilot]

Thats what GPU-Z shows. Idle, loading DCS to menu (6GB), loading Through the inferno mission (over 13GB) choosing A-10II (24GB) after that choosing F-14 (2 little spikes for each plane). After that leaving to menu, 24GB kept getting allocated. At the end, quit DCS.

Keep in mind that i'm driving very high ingame settings and double panel resolution SS for each eye. A huge part of VRAM is allocated for the display buffers.

The last graph shows RAM usage, around 32GB from 64GB.

Edited October 2, 2020 by Alec Delorean

[The_Nephilim]

Hmm I see now. which VR headset do you have currently? when I ran GPU-z it showed 8140 used but in fpsVR it was 7.7?

 

I am wondering which program is more accurate, as if I was loading over 8gb on the VRam that could account for the tiny stutters maybe I am not sure..

 

Was your 24GB over that by a small amount at any point during the test like 24100 or similar?..

 

Can you show your DCS Settings? are you getting decent FPS tho? looks like DCS is a Hog at your level of detail and all.

[dawgie79]

This problem was already known, and noticed by those who switch aircrafts or even restarts in even single player. 8-11GB limit comes very quickly as bottleneck.

 

I also believe the issue is optimization on ED's part. It wouldn't be really justifyable and even good businesspractice to optimize your product for such a small percentage of users only (those with the most expensive and new hardware) in an already niche market.

 

Makes no sense. SO I'm hoping ED is seriously looking into this.

[Gunnars Driver]

Hmm I see now. which VR headset do you have currently? when I ran GPU-z it showed 8140 used but in fpsVR it was 7.7?

 

I found a difference of about 200 Mb, not important for tuning or deciding.

 

Anyway: 1Gb is 1024 Mb so 7.7 = 7884 Mb. Not a big diff, actually about the same I have seen.

 

I would guess GPU-Z is more correct. Probably it is the same with VRAM as frame times in fpsvr: only counting the usage direct coupled to the game.

[RealDCSpilot]

Most of my current settings.

 

[RealDCSpilot]

options.lua

 

["graphics"] = {

["DOF"] = 0,

["LensEffects"] = 2,

["MSAA"] = 2,

["SSAA"] = 0,

["SSAO"] = 0,

["SSLR"] = 0,

["anisotropy"] = 4,

["aspect"] = 0.9,

["chimneySmokeDensity"] = 10,

["civTraffic"] = "low",

["clouds"] = 1,

["clutterMaxDistance"] = 800,

["cockpitGI"] = 1,

["effects"] = 3,

["flatTerrainShadows"] = 1,

["forestDistanceFactor"] = 1,

["fullScreen"] = false,

["heatBlr"] = 1,

["height"] = 1600,

["lights"] = 2,

["messagesFontScale"] = 1,

["motionBlur"] = 0,

["multiMonitorSetup"] = "1camera",

["outputGamma"] = 2.2,

["preloadRadius"] = 150000,

["rainDroplets"] = true,

["scaleGui"] = 1,

["shadowTree"] = false,

["shadows"] = 4,

["sync"] = false,

["terrainTextures"] = "max",

["textures"] = 2,

["treesVisibility"] = 10000,

["useDeferredShading"] = 1,

["visibRange"] = "High",

["water"] = 2,

["width"] = 1440,

 

autoexec.cfg

 

options.graphics.stereo_mode_use_shared_parser = false

disable_write_track = true

no_device_hotplug = true

[The_Nephilim]

does setting the aspect ratio do anything in VR or is that for the monitor?

[FoxTwo]

I also believe the issue is optimization on ED's part. It wouldn't be really justifyable and even good businesspractice to optimize your product for such a small percentage of users only (those with the most expensive and new hardware) in an already niche market.

 

Makes no sense. SO I'm hoping ED is seriously looking into this.

 

 

lol

[dawgie79]

lol

 

Just say what you want to say?

[FoxTwo]

Just say what you want to say?

 

I'm pretty sure I did.

 

But if you like I go into a lengthy explanation about how it's very likely that internally ED considers VR to be a niche at best, and while they occasionally throw it a bone, very little work will be put into making the engine more efficient for it in the short or even medium term.

 

We've been asking for fixes and changes for years. The 3090 shines a light on the problem but it's not like it was some kind of secret beforehand.

[dawgie79]

I'm pretty sure I did.

 

But if you like I go into a lengthy explanation about how it's very likely that internally ED considers VR to be a niche at best, and while they occasionally throw it a bone, very little work will be put into making the engine more efficient for it in the short or even medium term.

 

We've been asking for fixes and changes for years. The 3090 shines a light on the problem but it's not like it was some kind of secret beforehand.

 

Well, if it's not too much trouble, I would like to hear read your insights about ED's considerations regarding VR? Every few years with the introduction of new GPUs this comes to light. Also, every few years there seems to be a minor/major graphics overhaul (2.5.0 -> 2.5.6).

 

Because, although I'm still relatively new to DCS (a little over 2yrs and counting :) ), from what I've gathered in the interviews ED has given over the years, the legacy code and therefor engine updates (to Vulkan for instance) is their biggest gripe, and is related to performance on pancake as well as VR. Right? Or I've been sleeping the past 20yrs, regarding engines/graphics/performance/rendering wise. :P

[RealDCSpilot]

@The_Nephilim

 

I think aspect ratio is not that important for the VR mirror, but maybe it's helping with something if it's set to 1:1 panel resolution. Usually this is all forced by the VR SDK and DCS settings for res and aspect ratio are ignored.

As an update, i also set visibility range to extreme now. No problem for the 3090, it's amazing how far i can push the game settings now.

Edited October 2, 2020 by Alec Delorean

[hansangb]

I also believe the issue is optimization on ED's part. It wouldn't be really justifyable and even good businesspractice to optimize your product for such a small percentage of users only (those with the most expensive and new hardware) in an already niche market.

 

Makes no sense. SO I'm hoping ED is seriously looking into this.

 

 

VR is the future of flight sim. It's a forgone conclusion. We can argue the adoption curve aka affordability of it. But it's the future.

 

The tech field is littered with dominant players who missed out on a shift. WordPerfect being late to Windows environment caused its demise. Novell not taking NT serious (for good technical reasons or not) caused them great harm.

 

So as ED updates the core (hard work, I'm willing to give them slack), the goal should be to prioritize VR experience. It's more demanding so that's the high bar that they should attack.

[dawgie79]

VR is the future of flight sim. It's a forgone conclusion. We can argue the adoption curve aka affordability of it. But it's the future.

 

The tech field is littered with dominant players who missed out on a shift. WordPerfect being late to Windows environment caused its demise. Novell not taking NT serious (for good technical reasons or not) caused them great harm.

 

So as ED updates the core (hard work, I'm willing to give them slack), the goal should be to prioritize VR experience. It's more demanding so that's the high bar that they should attack.

 

Agree.

 

So, a niche in a niche in a niche then. ;)

[Taz1004]

It's not easy to do both well with current gen game engines. MSFS 2020 launched without VR. Codemasters F1 2020 launched without VR. Half Life Alyx was VR only. There aren't that many that does both well and efficiently.

 

It's not just initial development but upkeep. Anything you change, you have to make sure it works in both VR and 2D. On a game that's constantly updating like DCS, that's a big deal. It's not as simple as make a game for VR and then tell the game engine to convert it to 2D. That may be for next gen game engines but not currently.

 

If you step back and look at the bigger picture, DCS is actually one of the better ones. You'll look back one day and say this was the early days of VR.

Edited October 2, 2020 by Taz1004

[imacken]

Simple reality, dcs in 2d uses half (5gb) the vram as it does in 3d (9-10.8 gb), on my kit below, I did some basic numbers using the new after burner, and you can see it Maloc / Free ING the vram, whilst a memory leak may be present, I don't think that's the problem the op is seeing. I think it's as simple as we are driving over twice the the pixels...

 

It's also the reason I went the 3090 route.

 

Certainly on my 4K monitor that’s not the case. I see my 2080Ti being maxed out on VRAM in various 2D scenarios.

 

Can’t remember what res you are running in 2D.