qemu-img convert burning CPU for nothing

I'm trying to reduce the usage of a qcow2 image. I did the following: qemu-img convert -p -f qcow2 -O qcow2 my_img.qcow2.backup my_img.qcow2 I outputs 200192 bytes and progress is stuck at 0.00%. CPU usage is pegged at 100% and I let it go for 2 hours. The input image file is 160G. Also, iotop says that there's no disk usage. What could qemu-img possibly be doing that's wasting this much time? Also, I should mention, I've tried using raw output format and it does the same thing.