I just benchmarked riofs compared to s3fs. My test case was a relatively simple bash script that ran pngquant on each .png it found. On a testbucket with ~70 images of which ~20 where png (spread over a lot of subdirectories, which prob slows things down) the results where:
So for this testcase riofs is ~15x faster! Setup was also very straightforward, although the docs are somewhat terse.
Regarding the fact that the script still took 15.9s: it's not very efficient, also actually running pngquant on png's is a cpu intensive process.