Performance. Primary author of the [[http://www.dtracebook.com|DTrace book]], where I developed some examples for %%FreeBSD%% 7.1. Also wrote the %%DTraceToolkit%%, some of which is being ported to /usr/share/dtrace/toolkit/, and previously worked on DTrace & ZFS @Sun. I hope to one day edit the [[PmcTools]] page and show awesome things.