Memory usage of GPU driver

What is the memory usage of GPU driver?

Before I start any CUDA calculations, the amount of free and allocated memory is typically like this:

Free and allocated memory at start is 2872 MB, 198 MB

(I calculate it like this)

size_t free, total, allocated;

	free = 0;

	total = 0;

	cudaMemGetInfo(&free, &total);

	allocated = total - free;

	mexPrintf("Free and allocated memory during calculation of denoised data new is %lu MB, %lu MB \n",free/(1024*1024), allocated/(1024*1024));

At first I thought that I’ve forgotten to free some variables but I get the same result after a reboot. How much global memory does the GPU driver use? I use a GTX 580 with 3 GB of memory.

It varies between drivers and platforms, but a few hundred MB is about right.