3 files changed, 25 insertions, 14 deletions
diff --git a/host/docs/usrp2.rst b/host/docs/usrp2.rst
index 09987b3fa..aff0d0454 100644
--- a/host/docs/usrp2.rst
+++ b/host/docs/usrp2.rst
@@ -158,10 +158,25 @@ buffer incoming samples faster than they can be processed.
 However, if you application cannot process samples fast enough,
 no amount of buffering can save you.
 
+By default, the UHD will try to request a reasonably large buffer size for both send and receive.
+A warning will be printed on instantiation if the actual buffer size is insufficient.
+See the OS specific notes below:
+
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+OS specific notes
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+On linux, the maximum buffer sizes are capped by the sysctl values
+**net.core.rmem_max** and **net.core.wmem_max**.
+To change the maximum values, run the following commands:
+::
+
+    sudo sysctl -w net.core.rmem_max=<new value>
+    sudo sysctl -w net.core.wmem_max=<new value>
+
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Device address params
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-To set the size of the buffers,
+To manually set the size of the buffers,
 the usrp2 will accept two optional parameters in the device address.
 Each parameter will accept a numeric value for the number of bytes.
 
@@ -172,14 +187,3 @@ Example, set the args string to the following:
 ::
 
     addr=192.168.10.2, recv_buff_size=100e6
-
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-OS specific notes
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-On linux, the maximum buffer sizes are capped by the sysctl values
-**net.core.rmem_max** and **net.core.wmem_max**.
-To change the maximum values, run the following commands:
-::
-
-    sudo sysctl -w net.core.rmem_max=<new value>
-    sudo sysctl -w net.core.wmem_max=<new value>
diff --git a/host/lib/transport/udp_zero_copy_asio.cpp b/host/lib/transport/udp_zero_copy_asio.cpp
index c3c02707e..7f9292d24 100644
--- a/host/lib/transport/udp_zero_copy_asio.cpp
+++ b/host/lib/transport/udp_zero_copy_asio.cpp
@@ -27,7 +27,8 @@ using namespace uhd::transport;
 /***********************************************************************
  * Constants
  **********************************************************************/
-static const size_t MIN_SOCK_BUFF_SIZE = size_t(100e3);
+//enough buffering for half a second of samples at full rate on usrp2
+static const size_t MIN_SOCK_BUFF_SIZE = size_t(sizeof(boost::uint32_t) * 25e6 * 0.5);
 static const size_t MAX_DGRAM_SIZE = 1500; //assume max size on send and recv
 static const double RECV_TIMEOUT = 0.1; //100 ms
 
@@ -159,6 +160,12 @@ template<typename Opt> static void resize_buff_helper(
     //otherwise, ensure that the buffer is at least the minimum size
     else if (udp_trans->get_buff_size<Opt>() < MIN_SOCK_BUFF_SIZE){
         resize_buff_helper<Opt>(udp_trans, MIN_SOCK_BUFF_SIZE, name);
+        if (udp_trans->get_buff_size<Opt>() < MIN_SOCK_BUFF_SIZE){
+            std::cerr << boost::format(
+                "Warning: the %s buffer size is smaller than the recommended size of %d bytes.\n"
+                "    See the USRP2 application notes on buffer resizing."
+            ) % name % MIN_SOCK_BUFF_SIZE << std::endl;
+        }
     }
 }
 
diff --git a/host/lib/usrp/usrp2/usrp2_iface.cpp b/host/lib/usrp/usrp2/usrp2_iface.cpp
index 83e98904e..66a1a57f6 100644
--- a/host/lib/usrp/usrp2/usrp2_iface.cpp
+++ b/host/lib/usrp/usrp2/usrp2_iface.cpp
@@ -200,7 +200,7 @@ private:
         //send and recv
         usrp2_ctrl_data_t in_data = this->ctrl_send_and_recv(out_data);
         UHD_ASSERT_THROW(htonl(in_data.id) == USRP2_CTRL_ID_WOAH_I_DEFINITELY_PEEKED_IT_DUDE);
-        return T(ntohl(out_data.data.poke_args.data));
+        return T(ntohl(in_data.data.poke_args.data));
     }
 
 };