register_pid
register_pid(sched, thread__tid(migrant), thread__comm_str(migrant));
waker = register_pid(sched, sample->tid, "<unknown>");
wakee = register_pid(sched, pid, comm);
prev = register_pid(sched, prev_pid, prev_comm);
next = register_pid(sched, next_pid, next_comm);
register_pid(sched, thread__tid(parent), thread__comm_str(parent));
register_pid(sched, thread__tid(child), thread__comm_str(child));