There isn't too much fun about the Linux 3.11 EXT4 changes for this mature and widely-used Linux file-system, but there is some performance tuning. Ts'o notes, "In the optimizations category, two major optimizations deserve mention. The first is that ext4_writepages() is now used for nodelalloc and ext3 compatibility mode. This allows writes to be submitted much more efficiently as a single bio request, instead of being sent as individual 4k writes into the block layer (which then relied on the elevator code to coalesce the requests in the block queue). Secondly, the extent cache shrink mechanism, which was introduce in 3.9, no longer has a scalability bottleneck caused by the i_es_lru spinlock. Other optimizations include some changes to reduce CPU usage and to avoid issuing empty commits unnecessarily."
Other work includes bug-fixes and code clean-ups for the EXT4 file-system in Linux 3.11 The pull request can be viewed on the mailing list.