Glad it was useful and motivating! This one I feel a bit bad about, because I wanted to write a patch and test that hypothesis, but I didn&#x27;t (yet) make the time for it.<p>I <i>feel</i> like I could after maybe ~30h (really I don&#x27;t have enough information to determine beyond it probably being between 10 and 100 hours) of focused effort. I did read a bunch of <i>The Design and Implementation of FreeBSD</i> and I felt like I could understand it reasonably well, using the mental models I picked up studying xv6.<p>The reasons why I didn&#x27;t do it (yet) are interesting in themselves. There was nothing in particular that I felt was missing from FreeBSD, and I hadn&#x27;t used the &quot;advanced&quot; parts of the OS enough to run into any bugs. Because of this I think I lacked a sense of ownership, and the artificiality of a bug hunting activity caught up to me, motivation-wise. To do this I think you need to be motivated to dive into the nitty-gritty of a particular part of the OS, in addition to having a good understanding of the OS as a whole. Instead I ended up exploring some of the more advanced parts of FreeBSD (Jails and ZFS) with <a href="http:&#x2F;&#x2F;experiments.oskarth.com&#x2F;netpowder&#x2F;" rel="nofollow">http:&#x2F;&#x2F;experiments.oskarth.com&#x2F;netpowder&#x2F;</a> - hopefully I will find something useful that I want to either extend or a bug I want to fix, or perhaps I get to test the hypothesis with something completely different (such as Mirage OS).