>Out of interest, what are your reasons for not having a peer reviewed article on this? Lack of familiarity of the process and/or time, would be my guess?
Partially...the part in question is the btree indexing. This is important because it is a core part of the filesystem but it is also the least exotic part of the FS.
The part that is much more performance critical is how do we use that index to track block reference counts and maintain snapshot integrity. Much of my initial work here was expanded by Yan Zheng, and I think his improvements are a better topic for research papers.
Here is a paper where they tried to replace the btrfs back reference tracking and measured some differences: