This works by calling C<getpid ()> on every iteration of the loop,
and thus this might slow down your event loop if you do a lot of loop
iterations and little real work, but is usually not noticeable (on my
-GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
-without a system call and thus I<very> fast, but my GNU/Linux system also has
-C<pthread_atfork> which is even faster).
+GNU/Linux system for example, C<getpid> is actually a simple 5-insn
+sequence without a system call and thus I<very> fast, but my GNU/Linux
+system also has C<pthread_atfork> which is even faster). (Update: glibc
+versions 2.25 apparently removed the C<getpid> optimisation again).
The big advantage of this flag is that you can forget about fork (and
forget about forgetting to tell libev about forking, although you still