We also got a very weird result with test of the filewalker and GC on BTRFS and ext4.
We have a benchmark tool for the filewalkers and the garbage collector: storj/cmd/tools/filewalker-benchmark at main · storj/storj · GitHub
git clone https://github.com/storj/storj.git
cd /mnt/x
go run ~/storj/cmd/tools/filewalker-benchmark