Packaged with liquid are benchmarks to determine the speed each signal processing element can run on your machine.

http://liquidsdr.org/doc/benchmarks/

Here you'll find a quick benchmark shootout between a few inexpensive ARM-based platforms including the Raspberry Pi B+, the Raspberry Pi 2 B (names can be confusing), and an old Beagle Bone I had lying around.

http://liquidsdr.org/blog/raspberry-pi2-benchmarks/

There's been a lot of hype about the Raspberry Pi 3's performance, but how does it fare with signal processing for software-define radios? Here are some benchmarks for multi-threaded performance with liquid-dsp.

http://liquidsdr.org/blog/raspberry-pi3-benchmarks/