use polling instead of syscall

net/uring/io_uring.c

@@ -18,6 +18,19 @@ typedef struct io_uring go_uring;
 typedef struct msghdr go_msghdr;
 typedef struct iovec go_iovec;
 typedef struct sockaddr_in go_sockaddr_in;
+typedef struct io_uring_params go_io_uring_params;
+
+static int initialize(struct io_uring *ring, int fd) {
+	struct io_uring_params params;
+    memset(&params, 0, sizeof(params));
+    params.flags |= IORING_SETUP_SQPOLL;
+    params.sq_thread_idle = 1000; // 1s
+    io_uring_queue_init_params(16, ring, &params); // 16: size of ring
+    int ret;
+    ret = io_uring_register_files(ring, &fd, 1);
+    // TODO: Do we need to unregister files on close, or is Closing the uring enough?
+    return ret;
+}
 
 // Wait for a completion to be available, fetch the data
 static uint64_t receive_into(struct io_uring *ring) {
@@ -62,7 +75,7 @@ static uint16_t port(struct sockaddr_in *sa) {
 
 // submit a recvmsg request via liburing
 // TODO: What recvfrom support arrives, maybe use that instead?
-static int submit_recvmsg_request(int sock, struct io_uring *ring, struct msghdr *mhdr, struct iovec *iov, struct sockaddr_in *sender, char *buf, int buflen, size_t idx) {
+static int submit_recvmsg_request(struct io_uring *ring, struct msghdr *mhdr, struct iovec *iov, struct sockaddr_in *sender, char *buf, int buflen, size_t idx) {
     iov->iov_base = buf;
     iov->iov_len = buflen;
 
@@ -73,7 +86,8 @@ static int submit_recvmsg_request(int sock, struct io_uring *ring, struct msghdr
     mhdr->msg_namelen = sizeof(struct sockaddr_in);
 
     struct io_uring_sqe *sqe = io_uring_get_sqe(ring);
-    io_uring_prep_recvmsg(sqe, sock, mhdr, 0);
+    io_uring_prep_recvmsg(sqe, 0, mhdr, 0); // use the 0th file in the list of registered fds
+    io_uring_sqe_set_flags(sqe, IOSQE_FIXED_FILE);
     io_uring_sqe_set_data(sqe, (void *)(idx));
     io_uring_submit(ring);
 

net/uring/io_uring_linux.go

@@ -56,13 +56,16 @@ func NewUDPConn(conn *net.UDPConn) (*UDPConn, error) {
 	}
 	r := new(C.go_uring)
 
-	const queue_depth = 16 // TODO: What value to use here?
-	C.io_uring_queue_init(queue_depth, r, 0)
+	fd := C.int(file.Fd())
+	ret := C.initialize(r, fd)
+	if ret < 0 {
+		return nil, fmt.Errorf("uring initialization failed: %d", ret)
+	}
 	u := &UDPConn{
 		ptr:   r,
 		conn:  conn,
 		file:  file,
-		fd:    C.int(file.Fd()),
+		fd:    fd,
 		local: conn.LocalAddr(),
 	}
 	for i := range u.reqs {
@@ -84,7 +87,7 @@ type req struct {
 func (u *UDPConn) submitRequest(idx int) error {
 	r := &u.reqs[idx]
 	// TODO: make a C struct instead of a Go struct, and pass that in, to simplify call sites.
-	errno := C.submit_recvmsg_request(u.fd, u.ptr, &r.mhdr, &r.iov, &r.sa, (*C.char)(unsafe.Pointer(&r.buf[0])), C.int(len(r.buf)), C.size_t(idx))
+	errno := C.submit_recvmsg_request(u.ptr, &r.mhdr, &r.iov, &r.sa, (*C.char)(unsafe.Pointer(&r.buf[0])), C.int(len(r.buf)), C.size_t(idx))
 	if errno < 0 {
 		return fmt.Errorf("uring.submitRequest failed: %v", errno) // TODO: Improve
 	}
@@ -96,8 +99,8 @@ func (u *UDPConn) ReadFromNetaddr(buf []byte) (int, netaddr.IPPort, error) {
 		return 0, netaddr.IPPort{}, errors.New("invalid uring.UDPConn")
 	}
 	nidx := C.receive_into(u.ptr)
-	if int64(nidx) == -1 {
-		return 0, netaddr.IPPort{}, errors.New("something wrong")
+	if int64(nidx) < 0 {
+		return 0, netaddr.IPPort{}, fmt.Errorf("something wrong, errno %v", int64(nidx))
 	}
 	idx := uint32(nidx)
 	n := uint32(nidx >> 32)