Built an attoparsec parser for timestamps, and unsurprisingly it's 15 times faster parsing ByteStrings with it than the old String parser. The surprising thing to me was that converting a String to a ByteString and using the new parser is 10 times as fast as the old parser despite the conversion overhead. A nice immediate speedup for many parts of git-annex!

Of course timestamp parsing is not a major cost center in git-annex, but benchmarking git annex whereis run on 1000 files, there is a real speedup already, approximately 4%.