Windows 8 high idle VRAM usage

Wow. So almost 25% of the GTX 690's 2GB frame buffer is used by Windows 8 just when idling at 4K. And it uses way more than Windows 7 (over 2x at 1080p!) despite missing marquee Aero features such as Glass translucency/blur and Flip 3D. I have a strong feeling it's Metro and/or WDDM 1.3 hogging all that VRAM.

This means Windows 8 is not a good OS for high-res gaming (e.g. 4K, surround) because the amount of VRAM that Aero/DWM uses is directly related to screen resolution. In Windows 7, you can free up all that video memory by disabling Aero, but there's no way to do it in Windows 8 since DWM is required for Metro and apps to function.

I'm not sure if Windows 8 automatically unloads the occupied VRAM as needed if it detects that a game or other app requires more. Or if it automatically disables desktop composition when running fullscreen games as Windows 7 is supposed to do but almost never does. But we can't test any of this because Windows 8 doesn't allow us to flip Aero on/off.

High Res Gaming. Do you have Aero Disabled? You should. Pics because it did happen. - EVGA Forums

You'll notice per above that disabling Aero in Windows 7 raises FPS across the board in addition to freeing up hundreds of MB's of VRAM. Since most games not named BF4 (an edge case due to DX11.1 CPU optimizations) perform the same on both OSes, it's safe to assume that disabling Aero in Windows 7 gives it an edge in performance over Windows 8.

Another benefit of Windows 7: Windowed gaming. DWM enforces V-Sync for games running in windowed or borderless windowed mode, causing mouse lag and stuttering/performance issues. Desktop composition can be disabled globally or on a per-app basis in Windows 7 but not in Windows 8. So Windows 7 is the way to go for streamers/ALT-TABers, surround monitors, emulators/old games, and anywhere else you need to game in a window.

TL;DR Windows 7 is a better gaming OS than Windows 8.

 

Good information. That is strange. 258MB used just to run a 1080p screen with basically a non-3D UI? I'd like to see what is being used by that vRAM.

 

Strange indeed. I imagine my 675mx would struggle at 1080p in windows 8, despite it having 4gb of vram. I'm also sure I wouldn't be able to have my dreamscene background in Win 8 either. Any idea if dreamscene even works for win 8?

 

My unscientific stab-in-the-dark is that the VRAM is being reserved by Metro (for smoother app switching and UI transitions?) and/or due to changes in WDDM 1.3.

I think you'll be fine, this is mainly a concern for people with 2GB or lower cards.

 

I'd like to know how to measure this. My card is 2GB and my screen is 3200x1800...

Edit - found it in GPU-z. Currently 344Mb on an external monitor @ 1680 x 1050.

Will restart and see what I get on the internal screen only and without the browser open.

284Mb for just the internal screen. 179Mb for just the external monitor, 316 for both.

 

In other words, the numbers in the graph above seem inflated for win 8.1. Bad drivers maybe?


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500MB with a 1440p and a 1080p. easily break 3GB running dead rising 3. I think it did hover to 800MBish on my setup with just windows.

used to have 4Gb on k5000m so no biggie, but now only 2 gb with m6100. More reason to play less games I guess.

 

Where's this link from and what is considered idle, how where the measurements taken?

Correct me if I'm wrong here but "frame buffer" is just the memory used for the display and in a muxless system with switchable graphics is controlled by the iGD, but I think maybe you are using it in the context of all VRAM. Other things use VRAM also. For example, loading big textures one can easily use Gigabytes of VRAM with just a 4 by 4 pixel window to display them.


Well here's some numbers from my 765M VRAM usage.

W8.1, normal GUI screen at 1920 x 1080, idle VRAM usage 62MB. Running a 3D app fullscreen, 230MB.

W7, normal GUI screen at 1920 x 1080, idle VRAM usage 57MB. Running the same 3D app fullscreen, 227MB.

Might be different drivers, forgot to check.

 

Desktop GTX 690, no iGPU. Taken from here: Debunking Common Myths About Video Memory - Tom’s Hardware

On the second page:

 

Here's using Desktop GT640 2GB, no iGD.

1400x900, idle GUI.
W7 Aero VRAM 60MB reserved, 41MB used, 13MB shared. Killing DWM in basic gets back ~30MB
W8.1 VRAM 60MB reserved, 48MB used, 12MB shared.

Note that you can use more than VRAM limit by swapping out to DRAM, bit like using the pagefile but not as harsh on the performance hit. As for gaming performance on each OS, best IMO to run the game itself and judge by the results.

 

Unfortunately Windows 8 isn't an option for me as far as gaming is concerned. The DWM forced V-Sync absolutely kills the games I must run in a window, and I have a lot of old games on disc and GOG that are incompatible with Windows 8.

 

That's a good reason.

Not sure what's going on with your windowed frame lock, I have no trouble running 1000's of FPS in a window on W8.1. Not trying to say one should use this or that OS, IMO leave that up to the individual, just trying to add some perspective.

 

It depends on the game/engine. Some run windowed w/o V-Sync, others do not. For example, Halo Custom Edition w/OpenSauce and mods is one which does not. It can be quite demanding and often drops below 60 FPS, so V-Sync kills performance and adds lots of input lag. I couldn't play it for most of last year because the Nvidia SLI flickering bug in DX9 forced me to run the afflicted games in a borderless window, which hurt performance too much in Windows 8. In Windows 7, you can overcome this with the disable desktop composition shim or killing DWM altogether, but you have no choice in Windows 8.

 

Disabled window manager, direct framebuffer rendering.

 

Exactly, problem with Windows 8 is you can't disable DWM.

 

Does this have to do with DWM only running in 32-bit color mode? Do you have a link for a free game that does this? Wouldn't mind taking a look. Thanks.

 

I have no idea, all my games are 32-bit color and some have different windowed V-Sync behavior. You can try it with D3D9+ games you own. Run them in a window w/V-Sync disabled and note the total absence of screen tearing and perceptibly increased input lag. FPS counter might show 60+ but that is a snapshot taken at the game engine level, therefore inaccurate in this case since true frame rate is limited to 60 by the compositor. And if you ever drop below refresh rate, you'll witness a large FPS drop and feel the resultant stutter since DWM uses double buffering.

 

The thing is that the direct rendering path in windows is extremely inefficient whenever you have... you know... one pixel that has to be updated outside the active context (even if the pixel doesn't move). Then performance tanks, and it's completely random.

Use the indirect rendering engine, or the dwm, and the screen context that only needs to be updated will be generated, and then drawn to the right area with sync to the rest of the desktop elements from buffer, and so on.

In practice, because the old components are so bad, you tend to gain performance this way. Just turn off transparency effects and so on if you don't want that.