From 4787c77bb089bf50a47207bbad55bd65a44769e4 Mon Sep 17 00:00:00 2001
From: Josh Blum <josh@joshknows.com>
Date: Sun, 20 Feb 2011 02:41:03 -0800
Subject: udp: try non-blocking recv first for performance

---
 host/lib/transport/udp_common.hpp    |  4 +++-
 host/lib/transport/udp_simple.cpp    |  4 +---
 host/lib/transport/udp_zero_copy.cpp | 24 ++++++++++++++----------
 3 files changed, 18 insertions(+), 14 deletions(-)

(limited to 'host')

diff --git a/host/lib/transport/udp_common.hpp b/host/lib/transport/udp_common.hpp
index 44067b5dc..47775d9c4 100644
--- a/host/lib/transport/udp_common.hpp
+++ b/host/lib/transport/udp_common.hpp
@@ -23,13 +23,15 @@
 
 namespace uhd{ namespace transport{
 
+    typedef boost::shared_ptr<boost::asio::ip::udp::socket> socket_sptr;
+
     /*!
      * Wait for the socket to become ready for a receive operation.
      * \param sock_fd the open socket file descriptor
      * \param timeout the timeout duration in seconds
      * \return true when the socket is ready for receive
      */
-    UHD_INLINE bool wait_for_recv(int sock_fd, double timeout){
+    UHD_INLINE bool wait_for_recv_ready(int sock_fd, double timeout){
         //setup timeval for timeout
         timeval tv;
         //If the tv_usec > 1 second on some platforms, select will
diff --git a/host/lib/transport/udp_simple.cpp b/host/lib/transport/udp_simple.cpp
index 094f570ff..1ee036d52 100644
--- a/host/lib/transport/udp_simple.cpp
+++ b/host/lib/transport/udp_simple.cpp
@@ -28,8 +28,6 @@ namespace asio = boost::asio;
  **********************************************************************/
 class udp_simple_impl : public udp_simple{
 public:
-    typedef boost::shared_ptr<asio::ip::udp::socket> socket_sptr;
-
     udp_simple_impl(
         const std::string &addr, const std::string &port, bool bcast, bool connect
     ):_connected(connect){
@@ -58,7 +56,7 @@ public:
     }
 
     size_t recv(const asio::mutable_buffer &buff, double timeout){
-        if (not wait_for_recv(_socket->native(), timeout)) return 0;
+        if (not wait_for_recv_ready(_socket->native(), timeout)) return 0;
         return _socket->receive(asio::buffer(buff));
     }
 
diff --git a/host/lib/transport/udp_zero_copy.cpp b/host/lib/transport/udp_zero_copy.cpp
index 793fc6fba..dda3bb547 100644
--- a/host/lib/transport/udp_zero_copy.cpp
+++ b/host/lib/transport/udp_zero_copy.cpp
@@ -139,7 +139,7 @@ public:
         asio::ip::udp::endpoint receiver_endpoint = *resolver.resolve(query);
 
         //create, open, and connect the socket
-        _socket = new asio::ip::udp::socket(_io_service);
+        _socket = socket_sptr(new asio::ip::udp::socket(_io_service));
         _socket->open(asio::ip::udp::v4());
         _socket->connect(receiver_endpoint);
         _sock_fd = _socket->native();
@@ -161,10 +161,6 @@ public:
         }
     }
 
-    ~udp_zero_copy_asio_impl(void){
-        delete _socket;
-    }
-
     //get size for internal socket buffer
     template <typename Opt> size_t get_buff_size(void) const{
         Opt option;
@@ -182,16 +178,24 @@ public:
     /*******************************************************************
      * Receive implementation:
      *
-     * Use select to perform a blocking receive with timeout.
+     * Perform a non-blocking receive for performance,
+     * and then fall back to a blocking receive with timeout.
      * Return the managed receive buffer with the new length.
      * When the caller is finished with the managed buffer,
      * the managed receive buffer is released back into the queue.
      ******************************************************************/
     managed_recv_buffer::sptr get_recv_buff(double timeout){
         udp_zero_copy_asio_mrb *mrb = NULL;
-        bool recv_ready = wait_for_recv(_sock_fd, timeout);
-        if (recv_ready and _pending_recv_buffs.pop_with_timed_wait(mrb, timeout)){
-            return mrb->get_new(::recv(_sock_fd, mrb->cast<char *>(), _recv_frame_size, 0));
+        if (_pending_recv_buffs.pop_with_timed_wait(mrb, timeout)){
+
+            #ifdef MSG_DONTWAIT //try a non-blocking recv() if supported
+            ssize_t ret = ::recv(_sock_fd, mrb->cast<char *>(), _recv_frame_size, MSG_DONTWAIT);
+            if (ret > 0) return mrb->get_new(ret);
+            #endif
+
+            if (wait_for_recv_ready(_sock_fd, timeout)) return mrb->get_new(
+                ::recv(_sock_fd, mrb->cast<char *>(), _recv_frame_size, 0)
+            );
         }
         return managed_recv_buffer::sptr();
     }
@@ -247,7 +251,7 @@ private:
 
     //asio guts -> socket and service
     asio::io_service        _io_service;
-    asio::ip::udp::socket   *_socket;
+    socket_sptr             _socket;
     int                     _sock_fd;
 };
 
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