i've found ktrace of libevent to be a little noisy and hard to read because it always passes in a changes pointer to kevent, even with a count of 0. this is just a tiny change to pass NULL in that case, so that kdump doesn't spit out big hex numbers at me.
Index: kqueue.c =================================================================== RCS file: /cvs/src/lib/libevent/kqueue.c,v retrieving revision 1.39 diff -u -p -r1.39 kqueue.c --- kqueue.c 3 Sep 2016 11:31:17 -0000 1.39 +++ kqueue.c 10 Jul 2017 01:25:57 -0000 @@ -190,7 +190,7 @@ kq_dispatch(struct event_base *base, voi ts_p = &ts; } - res = kevent(kqop->kq, changes, kqop->nchanges, + res = kevent(kqop->kq, kqop->nchanges ? changes : NULL, kqop->nchanges, events, kqop->nevents, ts_p); kqop->nchanges = 0; if (res == -1) {