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DirectX Window drops to 30fps when it is not the foreground window in Win7


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#1 ehmdjii   Members   -  Reputation: 234

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Posted 04 April 2013 - 07:23 AM

i have a directx game which runs in windowed mode on windows desktop.

 

as long as it has the focus it has precisely 60fps but when another window comes to the foreground it drops to 30fps.

 

i have noticed this on windows 7 and with a directx9 and directx11 renderer.

 

i am not sure if this is even a directx/windows problem or is related to the graphics card driver (i have nvidia GF250)



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#2 Amr0   Members   -  Reputation: 1035

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Posted 04 April 2013 - 09:11 AM

I've just tested with a couple of the samples that come with the DX SDK, and I've noticed similar behavior as well! I've become interested in knowing why, though I can't say I hate this behavior - for me knowing that a game will not eat up all my CPU and GPU power even though it's in the background is a good thing. I suspect it's the doing of the nvidia driver (I have a 9800GT, Win7).



#3 Dawoodoz   Members   -  Reputation: 290

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Posted 05 April 2013 - 05:17 AM

I think it is implemented in the DXUT code. One of the many reasons for throwing it away and making your own.


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#4 mhagain   Crossbones+   -  Reputation: 7467

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Posted 05 April 2013 - 05:28 AM

Likewise I'd consider this desirable behaviour.  If I bring another window to the foreground then I'd prefer that other window to get the lion's share of resorces.  The program that I send to the background is certainly not so awesome that I'd be happy for it to continue chewing through all of my system resources despite the fact that I'm not currently using it.


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#5 ehmdjii   Members   -  Reputation: 234

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Posted 05 April 2013 - 05:56 AM

Likewise I'd consider this desirable behaviour.  If I bring another window to the foreground then I'd prefer that other window to get the lion's share of resorces.  The program that I send to the background is certainly not so awesome that I'd be happy for it to continue chewing through all of my system resources despite the fact that I'm not currently using it.

 

i agree with that, still i believe that the developer should be able to control that.

 

(in my situation i have a very good reason for the background window to receive it's full performance)



#6 ehmdjii   Members   -  Reputation: 234

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Posted 05 April 2013 - 05:59 AM

I think it is implemented in the DXUT code. One of the many reasons for throwing it away and making your own.

 

actually i am using SharpDX wrapper to create my DX11 window.



#7 Erik Rufelt   Crossbones+   -  Reputation: 3107

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Posted 05 April 2013 - 07:14 AM

Are you using vsync?

I'm unsure how vsync works in window-mode in general, and especially for background windows.. but it's probably not as trivial as "make it work" for various reasons. Try disabling vsync when going into the background and manually cap the framerate to 60 or whatever refresh/rate the monitor is currently running at, if you want the same performance as in foreground mode. Relying on vsync in the background is probably not possible, and probably doesn't have that much benefit either. The user might be dragging windows on top of your game or using graphics in another application etc. The exact behavior probably also depends on if you have DWM enabled.



#8 Flimflam   Members   -  Reputation: 657

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Posted 06 April 2013 - 03:32 PM

I've run some SharpDX samples checking with both vsync on and off and I'm not seeing this behavior. 



#9 VladR   Members   -  Reputation: 722

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Posted 10 April 2013 - 01:25 PM

So,

 

You get EXACTLY 60 fps when running the game.

You get EXACTLY 30 fps when changing the focus.

 

 

For that, to not actually be the VSync, that would be an amazing coincidence between the scheduler and the driver...


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#10 SimonForsman   Crossbones+   -  Reputation: 5806

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Posted 10 April 2013 - 02:22 PM


Likewise I'd consider this desirable behaviour.  If I bring another window to the foreground then I'd prefer that other window to get the lion's share of resorces.  The program that I send to the background is certainly not so awesome that I'd be happy for it to continue chewing through all of my system resources despite the fact that I'm not currently using it.

 
i agree with that, still i believe that the developer should be able to control that.
 
(in my situation i have a very good reason for the background window to receive it's full performance)


The user should control that, not a developer of third party applications, if the user wants your application to keep chewing through resources while in the background he can raise its priority.

The drop to 30fps however is most likely caused by the graphics driver, especially if its not set to maximize performance (nvidia drivers should have default power management mode set to adaptive (atleast on mobile GPUs) and it would make sense for it to slow down rendering of things not in focus with that setting.

You should decouple rendering from logic if a lower framerate causes your application to function incorrectly.

Edited by SimonForsman, 10 April 2013 - 02:37 PM.

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