When running a single Dbench instance, all of the non-default mount options that were tested with the Btrfs file-system ended up resulting in performance improvements except for Zlib compression and the free inode cache, both of which resulted in measurable performance drops. The mount option resulting in the biggest gain was the nodatacow for disabling copy-on-writes, but this can be potentially dangerous if the system fails or loses power during writes where the data may not be written to the disk. The Btrfs space caching and LZO compression were two safe and worthwhile options for this test profile.
With the first FS-Mark run of 1000 files of 1MB size, all of the tested mount options except for enabling the free inode cache resulted in performance improvements. For this test, the biggest winners were enabling Zlib and LZO transparent file-system compression. (With the Linux 3.4 kernel will also be tests of the new Btrfs compression support in the near future.) Space caching and auto-defrag resulted in small performance boosts.
When not enforcing sync/fsync requests, the mount options were much the same, relatively speaking.