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diff --git a/host/docs/transport.rst b/host/docs/transport.rst deleted file mode 100644 index 88f787893..000000000 --- a/host/docs/transport.rst +++ /dev/null @@ -1,165 +0,0 @@ -======================================================================== -UHD - Transport Application Notes -======================================================================== - -.. contents:: Table of Contents - ------------------------------------------------------------------------- -Introduction ------------------------------------------------------------------------- -A transport is the layer between the packet interface and a device IO -interface. The advanced user can pass optional parameters into the underlying -transport layer through the device address. These optional parameters control -how the transport object allocates memory, resizes kernel buffers, spawns -threads, etc. When not spcified, the transport layer will use values for these -parameters that are known to perform well on a variety of systems. The -transport parameters are defined below for the various transports in the UHD -software: - ------------------------------------------------------------------------- -UDP Transport (Sockets) ------------------------------------------------------------------------- -The UDP transport is implemented with user-space sockets. -This means standard Berkeley sockets API using send()/recv(). - -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Transport parameters -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -The following parameters can be used to alter the transport's default behavior: - -* **recv_frame_size:** The size of a single receive buffer in bytes -* **num_recv_frames:** The number of receive buffers to allocate -* **send_frame_size:** The size of a single send buffer in bytes -* **num_send_frames:** The number of send buffers to allocate - -**Note1:** -**num_recv_frames** does not affect performance. - -**Note2:** -**num_send_frames** does not affect performance. - -**Note3:** -**recv_frame_size** and **send_frame_size** can be used to -increase or decrease the maximum number of samples per packet. -The frame sizes default to an MTU of 1472 bytes per IP/UDP packet -and may be increased if permitted by your network hardware. - -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Flow control parameters -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -The host-based flow control expects periodic update packets from the device. -These update packets inform the host of the last packet consumed by the device, -which allows the host to determine throttling conditions for the transmission of packets. -The following mechanisms affect the transmission of periodic update packets: - -* **ups_per_fifo:** The number of update packets for each FIFO's worth of bytes sent into the device -* **ups_per_sec:** The number of update packets per second (defaults to 20 updates per second) - -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Resize socket buffers -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -It may be useful to increase the size of the socket buffers to -move the burden of buffering samples into the kernel or to -buffer incoming samples faster than they can be processed. -However, if your application cannot process samples fast enough, -no amount of buffering can save you. -The following parameters can be used to alter socket's buffer sizes: - -* **recv_buff_size:** The desired size of the receive buffer in bytes -* **send_buff_size:** The desired size of the send buffer in bytes - -**Note:** Large send buffers tend to decrease transmit performance. - -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Latency Optimization -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Latency is a measurement of the time it takes a sample to travel between the host and device. -Most computer hardware and software is bandwidth optimized, which may negatively affect latency. -If your application has strict latency requirements, please consider the following notes: - -**Note1:** -The time taken by the device to populate a packet is proportional to the sample rate. -Therefore, to improve receive latency, configure the transport for a smaller frame size. - -**Note2:** -For overall latency improvements, -look for "Interrupt Coalescing" settings for your OS and ethernet chipset. -It seems the Intel ethernet chipsets offer fine-grained control in Linux. -Also, consult: - -* http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp?topic=/com.ibm.aix.prftungd/doc/prftungd/interrupt_coal.htm - -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Linux 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> - -Set the values permanently by editing **/etc/sysctl.conf**. - -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Windows specific notes -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -**UDP send fast-path:** -It is important to change the default UDP behavior such that -1500 byte packets still travel through the fast path of the sockets stack. -This can be adjusted with the FastSendDatagramThreshold registry key: - -* FastSendDatagramThreshold registry key documented here: - - * http://www.microsoft.com/windows/windowsmedia/howto/articles/optimize_web.aspx#appendix_e - -* Double click and run <install-path>/share/uhd/FastSendDatagramThreshold.reg -* A system reboot is recommended after the registry key change. - -**Power profile:** -The Windows power profile can seriously impact instantaneous bandwidth. -Application can take time to ramp-up to full performance capability. -It is recommended that users set the power profile to "high performance". - ------------------------------------------------------------------------- -USB Transport (LibUSB) ------------------------------------------------------------------------- -The USB transport is implemented with LibUSB. -LibUSB provides an asynchronous API for USB bulk transfers. - -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Transport parameters -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -The following parameters can be used to alter the transport's default behavior: - -* **recv_frame_size:** The size of a single receive transfers in bytes -* **num_recv_frames:** The number of simultaneous receive transfers -* **send_frame_size:** The size of a single send transfers in bytes -* **num_send_frames:** The number of simultaneous send transfers - -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Setup Udev for USB (Linux) -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -On Linux, Udev handles USB plug and unplug events. -The following commands install a Udev rule -so that non-root users may access the device: - -:: - - cd <install-path>/lib/uhd/utils - sudo cp uhd-usrp.rules /etc/udev/rules.d/ - sudo udevadm control --reload-rules - sudo udevadm trigger - -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Install USB driver (Windows) -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -A driver package must be installed to use a USB-based product with UHD software: - -* Download the driver from the UHD wiki page `here <http://files.ettus.com/binaries/misc/erllc_uhd_winusb_driver.zip>`_. -* Unzip the file into a known location. We will refer to this as the **<directory>**. -* Open the device manager and plug in the USRP device. You will see an unrecognized USB device in the device manager. -* Right click on the unrecognized USB device and select update/install driver software (may vary for your OS). -* In the driver installation wizard, select "browse for driver", browse to the **<directory>**, and select the **.inf** file. -* Continue through the installation wizard until the driver is installed. |