--- libev/ev_iouring.c	2019/08/17 05:30:16	1.3
+++ libev/ev_iouring.c	2019/12/22 15:05:32	1.7
@@ -49,8 +49,9 @@
  * e) why 3 mmaps instead of one? one would be more space-efficient,
  *    and I can't see what benefit three would have (other than being
  *    somehow resizable/relocatable, but that's apparently not possible).
+ *    (FIXME: newer kernels can use 2 mmaps only, need to look into this).
  * f) hmm, it's practiclaly undebuggable (gdb can't access the memory, and
-      the bizarre way structure offsets are commuinicated makes it hard to
+ *    the bizarre way structure offsets are communicated makes it hard to
  *    just print the ring buffer heads, even *iff* the memory were visible
  *    in gdb. but then, that's also ok, really.
  * g) well, you cannot specify a timeout when waiting for events. no,
@@ -60,8 +61,10 @@
  *    like a µ-optimisation by the io_uring author for his personal
  *    applications, to the detriment of everybody else who just wants
  *    an event loop. but, umm, ok, if that's all, it could be worse.
+ *    (FIXME: jens mentioned timeout commands, need to investigate)
  * h) there is a hardcoded limit of 4096 outstanding events. okay,
  *    at least there is no arbitrary low system-wide limit...
+ *    (FIXME: apparently, this was increased to 32768 in later kernels(
  * i) unlike linux aio, you *can* register more then the limit
  *    of fd events, and the kernel will "gracefully" signal an
  *    overflow, after which you could destroy and recreate the kernel
@@ -69,6 +72,7 @@
  *    totally insane, but kind of questions the point a high
  *    performance I/O framework when it doesn't really work
  *    under stress.
+ *    (FIXME: iouring should no longer drop events, need to investigate)
  * j) but, oh my! is has exactly the same bugs as the linux aio backend,
  *    where some undocumented poll combinations just fail.
  *    so we need epoll AGAIN as a fallback. AGAIN! epoll!! and of course,
@@ -363,7 +367,6 @@
 static void
 iouring_modify (EV_P_ int fd, int oev, int nev)
 {
-  fprintf (stderr,"modify %d (%d, %d) %d\n", fd, oev,nev, anfds[fd].eflags);//D
   if (ecb_expect_false (anfds [fd].eflags))
     {
       /* we handed this fd over to epoll, so undo this first */
@@ -473,8 +476,6 @@
       return;
     }
 
-  fprintf (stderr, "fd %d event, rearm\n", fd);//D
-
   /* feed events, we do not expect or handle POLLNVAL */
   fd_event (
     EV_A_
@@ -581,7 +582,7 @@
     /* no events, so maybe wait for some */
     iouring_tfd_update (EV_A_ timeout);
 
-  /* only enter the kernel if we have somethign to submit, or we need to wait */
+  /* only enter the kernel if we have something to submit, or we need to wait */
   if (timeout || iouring_to_submit)
     {
       int res;
@@ -611,12 +612,6 @@
   if (!epoll_init (EV_A_ 0))
     return 0;
 
-  ev_io_init  (EV_A_ &iouring_epoll_w, iouring_epoll_cb, backend_fd, EV_READ);
-  ev_set_priority (&iouring_epoll_w, EV_MAXPRI);
-
-  ev_io_init  (&iouring_tfd_w, iouring_tfd_cb, iouring_tfd, EV_READ);
-  ev_set_priority (&iouring_tfd_w, EV_MAXPRI);
-
   iouring_entries     = IOURING_INIT_ENTRIES;
   iouring_max_entries = 0;
 
@@ -626,6 +621,12 @@
       return 0;
     }
 
+  ev_io_init  (&iouring_epoll_w, iouring_epoll_cb, backend_fd, EV_READ);
+  ev_set_priority (&iouring_epoll_w, EV_MAXPRI);
+
+  ev_io_init  (&iouring_tfd_w, iouring_tfd_cb, iouring_tfd, EV_READ);
+  ev_set_priority (&iouring_tfd_w, EV_MAXPRI);
+
   ev_io_start (EV_A_ &iouring_epoll_w);
   ev_unref (EV_A); /* watcher should not keep loop alive */