framebuffer over certain size : huge slowdown ?

[divide]

Help, I'm getting crazy with this problem :

I have a framebuffer+texture sized to the window size.
I get 60fps (vsync) as long as the window is small.

Then if I resize the window over a certain size, the framerate suddenly goes from 60fps to 5fps ! It's not a progressive slowdown, it just really kill the perf over a certain framebuffer size (like over 1400x600). The problem is a bit random, and it happens more often when I have 2 windows (with each his sized framebuffer) sharing the same OpenGL context.

Any idea ? I'm getting mad.
I get some random GL_OUT_OF_MEMORY errors, but I've checked with GPU-Z, only 200MB of VRAM is used (and only 40MB for my application !), which match the size of my textures.

System: Win7x64 NVIDIA GeForce GTX260 1.7GB driver 266.58

[_arts_]

If you got GL_OUT_OF_MEMORY, then you ran out of memory. Trust GL errors instead of your calculations which certainly don't include many hidden things.

[Aleksandar]

Instead of using GPU-Z, try to use NVX_gpu_memory_info in order to determine real memory allocation. But even that can be irrelevant, because the driver may fail to perform certain action and reallocate/free used memory. So, it is possible to have a pick in memory allocation which can be filtered out by sampling period in GPU-Z, or in your code.

[divide]

I'm quite sure I have no memory leak :
-I use very few textures, and I triple checked each is created and destroyed properly.
-I checked with NVX_gpu_memory_info and it says I still have 1.5Gb memory free to play with, so the GPU memory is definitely not full.

I really think something's fucked up, but not because VRAM is full. And hell, you do no fill 1.7GB memory at the very start of your program and 4-5 textures loaded :p

[divide]

Okay.... I thing I have something.
I started a fresh session this morning, and there was no bug anymore, no matter how hard I try, it worked perfectly.

Then I ran TV (Windows Media Center) for the news, and BAM the bug strike back. The previous days I also had TV running in parallel while working.

So this has something to do with either Windows Media Center, GPU video decoding or the way the video driver handle that.

[malexander]

We've had a couple of customer complains that our application was periodically hanging for several seconds, and it turned out that they had a web browser with hardware-accelerated flash video running (a video tutorial). So I'm tempted to say the GPU video decoding is doing something odd in the hardware (perhaps reserving a ton of memory?)