[ViewVC] Diff of: cvs/libev/ev

Comparing libev/ev_iouring.c (file contents):
Revision 1.3 by root, Sat Aug 17 05:30:16 2019 UTC vs.
Revision 1.13 by root, Sat Dec 28 03:29:50 2019 UTC

  *    without any syscalls. what's not to like?
  * d) ok, it's vastly more complex, but that's ok, really.
  * 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,
  *    seriously, the interface doesn't support a timeout. never seen _that_
  *    before. sure, you can use a timerfd, but that's another syscall
  *    you could have avoided. overall, this bizarre omission smells
  *    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
  *    state, a bit bigger, or fall back to e.g. poll. thats not
  *    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,
  *    this is completely undocumented, have I mantioned this already?
  * k) overall, the *API* itself is, I dare to say, not a total trainwreck.
  *    the big isuess with it are the bugs requiring epoll, which might
  *    or might not get fixed (do I hold my breath?).
  */
+/* TODO: use internal TIMEOUT */
+/* TODO: take advantage of single mmap, NODROP etc. */
+/* TODO: resize cq/sq size independently */
 #include <sys/timerfd.h>
 #include <sys/mman.h>
 #include <poll.h>
+#include <stdint.h>
 #define IOURING_INIT_ENTRIES 32
 /*****************************************************************************/
 /* syscall wrapdadoop - this section has the raw api/abi definitions */
 {
   __u8 opcode;
   __u8 flags;
   __u16 ioprio;
   __s32 fd;
+  union {
-  __u64 off;
+    __u64 off;
+    __u64 addr2;
+  };
   __u64 addr;
   __u32 len;
   union {
     __kernel_rwf_t rw_flags;
     __u32 fsync_flags;
     __u16 poll_events;
     __u32 sync_range_flags;
     __u32 msg_flags;
+    __u32 timeout_flags;
+    __u32 accept_flags;
+    __u32 cancel_flags;
+    __u32 open_flags;
+    __u32 statx_flags;
   };
   __u64 user_data;
   union {
     __u16 buf_index;
     __u64 __pad2[3];
   __u32 sq_entries;
   __u32 cq_entries;
   __u32 flags;
   __u32 sq_thread_cpu;
   __u32 sq_thread_idle;
+  __u32 features;
-  __u32 resv[5];
+  __u32 resv[4];
   struct io_sqring_offsets sq_off;
   struct io_cqring_offsets cq_off;
 };
+#define IORING_SETUP_CQSIZE 0x00000008
-#define IORING_OP_POLL_ADD    6
+#define IORING_OP_POLL_ADD        6
-#define IORING_OP_POLL_REMOVE 7
+#define IORING_OP_POLL_REMOVE     7
+#define IORING_OP_TIMEOUT        11
+#define IORING_OP_TIMEOUT_REMOVE 12
+/* relative or absolute, reference clock is CLOCK_MONOTONIC */
+struct iouring_kernel_timespec
+{
+  int64_t tv_sec;
+  long long tv_nsec;
+};
+#define IORING_TIMEOUT_ABS 0x00000001
 #define IORING_ENTER_GETEVENTS 0x01
 #define IORING_OFF_SQ_RING 0x00000000ULL
 #define IORING_OFF_CQ_RING 0x08000000ULL
 #define IORING_OFF_SQES	   0x10000000ULL
+#define IORING_FEAT_SINGLE_MMAP   0x00000001
+#define IORING_FEAT_NODROP        0x00000002
+#define IORING_FEAT_SUBMIT_STABLE 0x00000004
 inline_size
 int
 evsys_io_uring_setup (unsigned entries, struct io_uring_params *params)
 {
 iouring_tfd_cb (EV_P_ struct ev_io *w, int revents)
 {
   iouring_tfd_to = EV_TSTAMP_HUGE;
 }
-static void
-iouring_epoll_cb (EV_P_ struct ev_io *w, int revents)
-{
-  epoll_poll (EV_A_ 0);
-}
 /* called for full and partial cleanup */
 ecb_cold
 static int
 iouring_internal_destroy (EV_P)
 {
   if (iouring_sq_ring != MAP_FAILED) munmap (iouring_sq_ring, iouring_sq_ring_size);
   if (iouring_cq_ring != MAP_FAILED) munmap (iouring_cq_ring, iouring_cq_ring_size);
   if (iouring_sqes    != MAP_FAILED) munmap (iouring_sqes   , iouring_sqes_size   );
-  if (ev_is_active (&iouring_epoll_w)) ev_ref (EV_A); ev_io_stop (EV_A_ &iouring_epoll_w);
+  if (ev_is_active (&iouring_tfd_w))
-  if (ev_is_active (&iouring_tfd_w  )) ev_ref (EV_A); ev_io_stop (EV_A_ &iouring_tfd_w  );
+    {
+      ev_ref (EV_A);
+      ev_io_stop (EV_A_ &iouring_tfd_w);
+    }
 }
 ecb_cold
 static int
 iouring_internal_init (EV_P)
   iouring_tfd     = -1;
   iouring_sq_ring = MAP_FAILED;
   iouring_cq_ring = MAP_FAILED;
   iouring_sqes    = MAP_FAILED;
+  if (!have_monotonic) /* cannot really happen, but what if11 */
+    return -1;
   for (;;)
     {
       iouring_fd = evsys_io_uring_setup (iouring_entries, &params);
       if (iouring_fd >= 0)
         break; /* yippie */
       if (errno != EINVAL)
         return -1; /* we failed */
+#if TODO
+      if ((~params.features) & (IORING_FEAT_NODROP | IORING_FEATURE_SINGLE_MMAP))
+        return -1; /* we require the above features */
+#endif
       /* EINVAL: lots of possible reasons, but maybe
        * it is because we hit the unqueryable hardcoded size limit
        */
   iouring_internal_destroy (EV_A);
   while (iouring_internal_init (EV_A) < 0)
     ev_syserr ("(libev) io_uring_setup");
-  /* forking epoll should also effectively unregister all fds from the backend */
-  epoll_fork (EV_A);
-  /* epoll_fork already did this. hopefully */
-  /*fd_rearm_all (EV_A);*/
+  fd_rearm_all (EV_A);
-  ev_io_stop  (EV_A_ &iouring_epoll_w);
-  ev_io_set   (EV_A_ &iouring_epoll_w, backend_fd, EV_READ);
-  ev_io_start (EV_A_ &iouring_epoll_w);
   ev_io_stop  (EV_A_ &iouring_tfd_w);
   ev_io_set   (EV_A_ &iouring_tfd_w, iouring_tfd, EV_READ);
   ev_io_start (EV_A_ &iouring_tfd_w);
 }
 /*****************************************************************************/
 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 */
-      /* we do it manually because the optimisations on epoll_modify won't do us any good */
-      epoll_ctl (iouring_fd, EPOLL_CTL_DEL, fd, 0);
-      anfds [fd].eflags = 0;
-      oev = 0;
-    }
   if (oev)
     {
       /* we assume the sqe's are all "properly" initialised */
       struct io_uring_sqe *sqe = iouring_sqe_get (EV_A);
       sqe->opcode    = IORING_OP_POLL_REMOVE;
       sqe->fd        = fd;
-      sqe->user_data = -1;
+      /* Jens Axboe notified me that user_data is not what is documented, but is
+       * some kind of unique ID that has to match, otherwise the request cannot
+       * be removed. Since we don't *really* have that, we pass in the old
+       * generation counter - if that fails, too bad, it will hopefully be removed
+       * at close time and then be ignored. */
+      sqe->user_data = (uint32_t)fd | ((__u64)(uint32_t)anfds [fd].egen << 32);
       iouring_sqe_submit (EV_A_ sqe);
       /* increment generation counter to avoid handling old events */
       ++anfds [fd].egen;
     }
 {
   int      fd  = cqe->user_data & 0xffffffffU;
   uint32_t gen = cqe->user_data >> 32;
   int      res = cqe->res;
-  /* ignore fd removal events, if there are any. TODO: verify */
-  if (cqe->user_data == (__u64)-1)
-    abort ();//D
   assert (("libev: io_uring fd must be in-bounds", fd >= 0 && fd < anfdmax));
   /* documentation lies, of course. the result value is NOT like
    * normal syscalls, but like linux raw syscalls, i.e. negative
    * error numbers. fortunate, as otherwise there would be no way
    * to get error codes at all. still, why not document this?
    */
   /* ignore event if generation doesn't match */
+  /* other than skipping removal events, */
   /* this should actually be very rare */
   if (ecb_expect_false (gen != (uint32_t)anfds [fd].egen))
     return;
   if (ecb_expect_false (res < 0))
     {
-      if (res == -EINVAL)
+      /*TODO: EINVAL handling (was something failed with this fd)*/
-        {
+      /*TODO: EBUSY happens when?*/
-          /* we assume this error code means the fd/poll combination is buggy
-           * and fall back to epoll.
-           * this error code might also indicate a bug, but the kernel doesn't
-           * distinguish between those two conditions, so... sigh...
-           */
-          epoll_modify (EV_A_ fd, 0, anfds [fd].events);
-        }
-      else if (res == -EBADF)
+      if (res == -EBADF)
         {
           assert (("libev: event loop rejected bad fd", res != -EBADF));
           fd_kill (EV_A_ fd);
         }
       else
         }
       return;
     }
-  fprintf (stderr, "fd %d event, rearm\n", fd);//D
   /* feed events, we do not expect or handle POLLNVAL */
   fd_event (
     EV_A_
     fd,
     (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
 iouring_overflow (EV_P)
 {
   /* we have two options, resize the queue (by tearing down
    * everything and recreating it, or living with it
    * and polling.
-   * we implement this by resizing tghe queue, and, if that fails,
+   * we implement this by resizing the queue, and, if that fails,
    * we just recreate the state on every failure, which
    * kind of is a very inefficient poll.
    * one danger is, due to the bios toward lower fds,
    * we will only really get events for those, so
    * maybe we need a poll() fallback, after all.
   else
     {
       /* we hit the kernel limit, we should fall back to something else.
        * we can either poll() a few times and hope for the best,
        * poll always, or switch to epoll.
-       * since we use epoll anyways, go epoll.
+       * TODO: is this necessary with newer kernels?
        */
       iouring_internal_destroy (EV_A);
-      /* this should make it so that on return, we don'T call any uring functions */
+      /* this should make it so that on return, we don't call any uring functions */
       iouring_to_submit = 0;
       for (;;)
         {
           backend = epoll_init (EV_A_ 0);
     timeout = EV_TS_CONST (0.);
   else
     /* 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;
       EV_RELEASE_CB;
 inline_size
 int
 iouring_init (EV_P_ int flags)
 {
-  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;
   if (iouring_internal_init (EV_A) < 0)
     {
       iouring_internal_destroy (EV_A);
       return 0;
     }
-  ev_io_start (EV_A_ &iouring_epoll_w);
+  ev_io_init  (&iouring_tfd_w, iouring_tfd_cb, iouring_tfd, EV_READ);
-  ev_unref (EV_A); /* watcher should not keep loop alive */
+  ev_set_priority (&iouring_tfd_w, EV_MINPRI);
   ev_io_start (EV_A_ &iouring_tfd_w);
   ev_unref (EV_A); /* watcher should not keep loop alive */
   backend_modify = iouring_modify;
   backend_poll   = iouring_poll;
 inline_size
 void
 iouring_destroy (EV_P)
 {
   iouring_internal_destroy (EV_A);
-  epoll_destroy (EV_A);
 }

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Comparing libev/ev_iouring.c (file contents): Revision 1.3 by root, Sat Aug 17 05:30:16 2019 UTC vs. Revision 1.13 by root, Sat Dec 28 03:29:50 2019 UTC

Diff Legend

Comparing libev/ev_iouring.c (file contents):
Revision 1.3 by root, Sat Aug 17 05:30:16 2019 UTC vs.
Revision 1.13 by root, Sat Dec 28 03:29:50 2019 UTC