Perormance Tuning with Steam VR Graphs

[DRGN72]

Hi everyone,

The catchline: You are potentially leaving visual quality on the bench for no performance gain! Check your GPU usage, if it's not close to 100% you can do better! There, now that you are hooked....

 

The Situation:

I made a discovery for myself tonight while trying to help out a buddy. This could help anyone using steam VR, and conceptually anyone else on any other system via use of windows task manager performance graphs instead of Steam VR.

 

My buddy is using the vive and just updated his PC's ram. While using task manager to look at the usage of his new ram under DCS, noticed his GPU was only working 60-70% and he asked me if I knew why. I fired up my DCS to see what mine showed (I am a previous rift and vive user, now running the index) and found the same thing. Then i dove into the performance graphs to figure out why.

 

Steam VR GPU Performance Graph

To enable steam VR performance graphs, flip the toggle labeled as such in steam VR developer settings (I am using Beta)

 

The middle horizontal line on the graph represents an 11.1ms frame timing (90fps). Anything below this line will result in smooth 90fps. As soon as it goes above, the fps instantly switches to 45.

 

The top of the graph represents 22.2ms frame timing (45fps). anything above the 11.1 and below 22.2ms will result in 45fps. Anything off the top results in less than 45.

 

Colour coding is green (<11.1), Yellow (>11.1, <22.2ish), and red (>22ish). Note the graph turns red before exceeding 22.2 while still maintaining 45fps. Also note if you have turned off frame smoothing, you will see orange instead of yellow.

 

The Test Specimen:

Kept myself honest by doing all testing paused at the start of the Hornet's fly now, free flight, Nevada instant action. I recommend to actually apply this, do so paused in an environment where you do most of your playing (ie low level with lots of ground units, mid to high level with lots of bandits etc) as i think as soon as you hit the action, the empty desert tuning will be no good for you.

 

How to use it:

The further below the 11.1 or 22.2 (if above 11.1) lines you are, the less the GPU usage will be. Mine as i had configured was only working at 67%. So you can turn on features, up super sampling (if doing via steam vr, you need to restart to see the effect), etc to get closer to one of those lines, and while doing so will see no fps loss (provided you don't cross the line), increasing visual quality, and increasing gpu usage.

 

The GPU will approach 100% usage as the graph approaches either the 11.1 or 22.2 line. Above 11.1 it will switch to 45fps, and the GPU usage will drop again sharply. Above 22.2, visual quality will continue to increase, GPU will be pegged at or around 100, and the fps will drop since the GPU can't give any more.

 

My results:

I am running the index, and a GTX 1080,

 

With textures hi, view dist medium, 1024 displays, and everything else off, at 80% super sampling via steam I can just barely maintain 90fps with nothing going on (ie the start of that instant action).

 

I hate the no shadow look so I usually play with shadows low, terrain shadows flat, Cockpit global illumination, at 100% steam SS, and get steady 45fps when not in a city/airport, with something like 15ms frame timing. This results in only 55-65 GPU usage for me.

 

Tuning via the graphs, in that fly now as detailed above I was able to up the visibility range to high, and the steam SS to 170%, and still maintain the same fps most of the time, but now in the 90% usage range. I tried changing other settings up and down one at a time, and you can see their relative impact on the graph, but none had as large an effect as the increased SS for quality to me. It seems (and makes sense) that as you increase the SS, the impact of the other settings also scales up accordingly. In any case, I was quite impressed that i can actually now read the MPCD!

 

You may prioritize different settings, the idea is the same... get close to the line, but don't cross it. I'll no doubt have to go back and reduce my settings somewhat for actual play.

 

The attached pictures were taken with my phone through the headset lenses where applicable.

Edited January 23, 2020 by DRGN72

[DRGN72]

You can probably achieve the same on other VR/AR platforms using the windows performance manager. combined with the ingame FPS counter (right ctrl+ scrl Lock)

 

Anyway, I had never seen anything explaining how the graphs work, hope this helps someone out! If you are on the cusp of 90fps, but stuck at 45 most the time, you may as well turn the detail up!

 

 

The concept is the same for other frame rates that may be available, the lines on the graph would represent the following.

 

80Hz (12.5ms) drops to 40hz (25ms)

120HZ (8.3ms) drops to 60hz (16.6ms)

144hz (6.9ms) drops to 72hz (13.8ms)

Edited January 23, 2020 by DRGN72

[coldViPer]

Thanks, I'm quite new in VR world and trying to achieve some kind of balance between OK performance and OK eye candy. I have tried to fly without shadows and MSAA but I CAN'T. I have to keep them on. I know it's not wise with my setup. Mostly I can fly with steady 40 fps even in MP if there is no tomcats nearby :D Do I understand correctly that shadows and MSAA affects only CPU performance?

[speed-of-heat]

Im sort of aware of this; i assume your are using motionvector in auto? Or are you forcing?

 

And then which eye candy features, have most GPU impact and least CPU impact? Has anyone done the work on this? Or are we all playing whack-a-mole?

[SkipCarey]

just tested this, the whole graph filled to the top with red but my experience remained smooth are you certain it drops to 45 fps when it all red and to the top? also how are you measuring your GPU Usage?

[SkipCarey]

This is also plane dependent F14/Fa18 pegs me out down low and violent maneuvers to along with over cities but up high and over ocean not so much.

[Gnadentod]

... Do I understand correctly that shadows and MSAA affects only CPU performance?

No, MSAA is a classical when it comes to GPU dependance. Shadows in most cases aswell, VRAM and GPU of the card.

[speed-of-heat]

just tested this, the whole graph filled to the top with red but my experience remained smooth are you certain it drops to 45 fps when it all red and to the top? also how are you measuring your GPU Usage?

 

My experience is it drops to 45 when you get into yellow

[SkipCarey]

Well what about pegged all the way up red and as high as 28/29ms? Because my experience didnt seem to stutter at all? but im running a I7 9700 oc@4.6 but Turbos to 4.9mhz all cores synced(I know DCS only uses 2 cores )an RTX 2080, DCS on an NVME SSD also 64gb memory @3200mhz and an Asus ROG maximus XI Code,Im pretty sure it is very plane/map dependent but I just dont seem to get any ill effect from running pegged in the Red all the way up on the graph? is there away to record your GPU usage over time?Keep a log? in task manager anyone?

[speed-of-heat]

if you are at 90FPS all the way into the Red ... never sell that processor and GPU :)

 

For me on my spec i am pretty much locked at 45FPS in most scenarios, which is green /yellow 12 to 18ms, as soon as i get red i notice the frame rate decaying into low 40's or high 30's which creates some stuttering

Edited January 25, 2020 by speed-of-heat

[Gunnars Driver]

Well what about pegged all the way up red and as high as 28/29ms? Because my experience didnt seem to stutter at all? but im running a I7 9700 oc@4.6 but Turbos to 4.9mhz all cores synced(I know DCS only uses 2 cores )an RTX 2080, DCS on an NVME SSD also 64gb memory @3200mhz and an Asus ROG maximus XI Code,Im pretty sure it is very plane/map dependent but I just dont seem to get any ill effect from running pegged in the Red all the way up on the graph? is there away to record your GPU usage over time?Keep a log? in task manager anyone?

 

if you are at 90FPS all the way into the Red ... never sell that processor and GPU :)

 

If CPU OR GPU -time exceeds 11.1ms you cannot reach 90fps. Its nature laws, really.

1000ms/11.1111 = 90fps.

 

If you are Above 22.2ms you cannot reach 45fps.

 

With ASW or motionReprojection in auto, the computer will switch from 90 to 45 as soon as it cant produce 90fps( = when fram time is more than 11.1 ms) You will see 45 doubled frames in VR.

If fram time is more than 22.2 it can not longer procude one new frame for each needed and it will not(per definition) be a smooth ride.

This is a question avout perfsonal reference, if you dont have any problem with fram rate, dont dig into it. You might find things you didnt see and that might cost you either quality settings or $ :cry:

___________________________________________________

I use the fpsVR, might be something like steam VR graphs.

Green = time to produce frame less than 11ms = 90fps.

Amber= time to produce frame more than 11ms = 45fps.

Red = time to produce frame more than 22s = lower than 45 fps.

___________________________________________________

[SkipCarey]

since modern movies run at 26fps I suspect thats why I am not noticing a drop in FPS, either way it only goes into RED and above 22ms down low and during violent maneuvering over cities then quickly recovers back to yellow and green

[Gunnars Driver]

since modern movies run at 26fps I suspect thats why I am not noticing a drop in FPS, either way it only goes into RED and above 22ms down low and during violent maneuvering over cities then quickly recovers back to yellow and green

 

Cinema and computer fps is not really comparable.

 

Classic Cinema movies are per default 24 frames per second. In the cinema they show each frame twice( like ASW or reprojection with VR). This is to smoothen the picture and minimize the flicker.

 

The movie frame is shot during a short period and catches things that move during some time.

This means the picture is a bit ”un-sharp” due to motion blur. This makes the the human eye percieving it less like a still picture and helps make us see it as a smooth flow.

Computer frames are per default still frames with no motion blur.

 

I see a clear differens between 90 - 60 -45 fps in gaming.

90 is really good. 60 is ok. 45, it isnt perfect but acceptable. I can percieve that there is a lot of pictures coming after each other.

By accident my reverb starded in 60fps, i noticed the difference, it was okey but when reprojection put it to 30 fps I sure did not like it.

We are all different and percieve things different. If you are happy with it below 45, be really happy and dont start thinking about it. If you do, it might get expensive :-)

[DRGN72]

just tested this, the whole graph filled to the top with red but my experience remained smooth are you certain it drops to 45 fps when it all red and to the top? also how are you measuring your GPU Usage?

As best as I understand it, approaching the red is reaching the limits of the computer's ability to maintain reprojection targets (45hz in my case at 22.2)

 

I'm using windows task manager performance graphs to see the CPU usage

[Gunnars Driver]

As best as I understand it, approaching the red is reaching the limits of the computer's ability to maintain reprojection targets (45hz in my case at 22.2)

 

I'm using windows task manager performance graphs to see the CPU usage

 

 

Yes. Its simple math:

 

If the CPU or GPU need more time to produce a frame than the time available, the frame will not reach the screen/VR-headset in time and the FPS will drop below ”target”.

 

- For 90 fps there is 1/90second = 11.1ms time to produce each frame. Frametimes higher than 11.1ms can not reach 90fps.

 

- For 45fps its 1/45 seconds or 22.2ms. Frame times more than 22.2ms can not hit 45fps.

 

At least some software do not take all processor load in the calculation, possibly making true frametime a bit higher than what you see on the screen.

 

I use fpsVR:

Green below 11.1ms ( for my reverb 90hz)

Amber between 11.1 and 22.2 ( reprojection/ASW)

Red: more than 22.2ms