Not related to your specific question, but perhaps related to the hackathon. I'm not sure if the hackathon rules would allow it, but there's an old LD_PRELOAD hack for ext filesystems that speeds up readdir() calls by doing them in inode order (which is somewhat correlated to disk layout). It's here: spd_readdir.c Thought it was worth mentioning since speeding up I/O would probably have a more meaningful effect.