Does using Nvidia's Dynamic Super Resolution (DSR) at 4k more demanding on the GPU than using 4k native resolution?

I can either use a 4k monitor, or use a 1080 or 1440p monitor with Nvidia's Dynamic Super Resolution (DSR) at 4k. Which option is more demanding on the GPU/CPU, if any? In other words, will using DSR decrease the frame rate compared to using native resolution at the same resolution? I'm guessing that DSR is more demanding but I have no idea whether it is x1.01 or x2 more demanding.

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