1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
|
/*! \page page_usrp_x3x0_config System Configuration for USRP X3x0 Series
\tableofcontents
\section x3x0cfg_hostpc Configuring your Host PC
The USRP X3x0 is capable of delivering very fast sample rates to the
host PC, and even high-powered desktops can have trouble keeping up at
the higher rates. You can improve the performance of your host by
configuring a number of settings that affect the performance of your
computer.
These are:
- Kernel Version
- Network Configuration
- Power Management Configuration
- Real-Time & Priority Scheduling
- Building with ORC & Volk
These items are covered in more detail, below.
\subsection x3x0cfg_hostpc_kernel Kernel Version
Performance issues may be encountered with Linux kernels earlier than
3.11. Ettus Research strongly recommends using kernel version 3.11 or
higher for high sample rates.
\subsection x3x0cfg_hostpc_netcfg Network Configuration
When using Ethernet interfaces to communicate with the device, it is
necessary to configure a number of facets regarding your network
connection.
\subsubsection x3x0cfg_hostpc_netcfg_nwmgr Configuring NetworkManager
Fedora and Ubuntu both use NetworkManager to manage network connections.
Unfortunately, NetworkManager often tries to take control of a
connection and will disconnect the interface.
You should open your NetworkManager configuration and tell it to ignore
the network interface you are using. **This is not the same as simply
setting a static IP address.** You *must* tell NetworkManager to ignore
the interface.
\subsubsection x3x0cfg_hostpc_netcfg_ip Configuring the host's IP address
On a Linux system, you can add a static IP address very easily by using the 'ip' command:
sudo ip addr add 192.168.10.1/24 dev <interface>
Note that `<interface>` is usually something like `eth0`. You can discover the
names of the network interfaces in your computer by running:
ip addr show
\subsubsection x3x0cfg_hostpc_netcfg_sockbuff Configuring the Socket Buffers
It is necessary to increase the maximum size of the socket buffers to
avoid potential overflows and underruns at high sample rates. Add the
following entries into /etc/sysctl.conf (root privileges required):
net.core.rmem_max=33554432
net.core.wmem_max=33554432
Either restart the system or issue the following commands:
sudo sysctl -w net.core.rmem_max=33554432
sudo sysctl -w net.core.wmem_max=33554432
\subsubsection x3x0cfg_hostpc_netcfg_mtu Configuring the MTU
In order to achieve maximum performance, we recommend setting the MTU
size to 9000 for 10 GigE and 1500 for 1 GigE. It is possible to use
smaller MTUs, but this can affect performance. With some NICs, setting
the MTU too high can also cause issues. To set the MTU to 9000, you can
use the following command:
sudo ifconfig <interface> mtu 9000 # For 10 GigE
sudo ifconfig <interface> mtu 1500 # For 1 GigE
Using these MTUs will set the frame sizes for UHD communication to 8000
and 1472, respectively.
In some cases, specifying the frame size manually by adding the argument
`<send/recv>_frame_size=1472` can solve issues. Note that a frame
size of 1472 will limit the available sampling rate, although this is
not a problem on 1 GigE.
\subsubsection x3x0cfg_hostpc_netcfg_firewall Configuring the Firewall
Many Linux distributions come installed with a Firewall, by default. The
Firewall will often interfere with your ability to communicate with your
USRP. You should configure your firewall to "trust" the interface you
are using. Setting this properly depends on your OS and firewall
configuration method.
When using UHD software, if an IP address for the USRP-X Series device is not specified,
the software will use UDP broadcast packets to locate the USRP-X Series device.
On some systems, the firewall will block UDP broadcast packets.
It is recommended that you change or disable your firewall settings.
\subsubsection x3x0cfg_hostpc_netcfg_if Interface Configuration File (Fedora)
On Fedora systems, you can configure the network interface mostly from
one place (with the exception of the socket buffers). Each interface on
your system should have a file in:
/etc/sysconfig/network-scripts/
As an example, if your 1GigE interface is "em1", your "ifcfg-em1"
configuration file should look something like this, when configured for
use with a USRP X3xx:
TYPE="Ethernet"
BOOTPROTO="none"
IPADDR0="192.168.10.1"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="no"
IPV6_FAILURE_FATAL="no"
NAME="em1"
UUID="<specific to your device>"
ONBOOT="no"
HWADDR"<specific to your device>"
PEERDNS="yes"
PEERROUTES="yes"
ZONE="trusted"
MTU="9000"
NM_MANAGED="no"
The above file was generated and modified on a Fedora 20 system.
\subsection x3x0cfg_hostpc_pwr Power Management
Power management on the host system attempts to save power by reducing
clock frequencies or even powering off devices while not in use. This
can lead to significant performance issues when trying to operate at
high sample rates. Ettus Research strongly recommends disabling all
power management.
\subsubsection x3x0cfg_hostpc_pwr_cpugov Setting the CPU Governors
In Linux, the CPU governors dictate the frequency at which the CPU
operates and attempt to reduce the CPU frequencies at certain times to
save power. When running at high sample rates, reduction of CPU
frequencies can cause significant performance issues. To prevent those
issues, set the governor to "performance".
\b Ubuntu:
1. Install cpufrequtils:
sudo apt-get install cpufrequtils
2. Edit `/etc/init.d/cpufrequtils` and set `GOVERNOR="performance"` on the
appropriate line (run as root):
sed s/^GOVERNOR=.*$/GOVERNOR=\"performance\"/g /etc/init.d/cpufrequtils > /etc/init.d/cpufrequtils
3. Restart cpufrequtils:
sudo /etc/init.d/cpufrequtils restart
\b Fedora:
sudo cpupower frequency-set -g performance
\subsection x3x0cfg_hostpc_rtprio Real-Time & Priority Scheduling
Enabling real-time and priority scheduling can improve the total
processing throughput of your application. Priority scheduling should be
enabled for UHD, and real-time scheduling can be enabled by your
application.
\subsubsection x3x0cfg_hostpc_rtprio_thread Thread Priority Scheduling with UHD
For information regarding how to enable priority scheduling for UHD on
your system, please see \ref page_general.
\subsubsection x3x0cfg_hostpc_rtprio_app Real-Time Scheduling in your Application
Please note that turning on real-time scheduling in your application
**may lock up your computer** if the processor cannot keep up with the
application. You should generally avoid using real-time scheduling
unless you need to.
Real-time scheduling is enabled via different methods depending on your
application and operating system. In GNU Radio Companion, it can be
turned on in each individual flowgraph.
\subsection x3x0cfg_hostpc_volk Building with ORC & Volk
Especially when running high-performance applications, processing
performance can be dramatically improved by SIMD instructions. UHD uses
ORC to provide SIMD capability, and GNU Radio includes a SIMD library
called "Volk". These should both be used to guarantee optimum
performance.
\subsubsection x3x0cfg_hostpc_volk_orc Compiling UHD with ORC
ORC, the <a href="http://code.entropywave.com/orc/">Oil Runtime Compiler</a>,
is a third-party compiler that UHD uses to create efficient SIMD code for
your particular computer. ORC is generally easily installed from your
OS's package manager.
On Fedora:
$ sudo yum update; sudo yum install orc-compiler orc-devel
On Ubuntu:
$ sudo apt-get update; sudo apt-get install liborc-<version> liborc-<version>-dev
After installing ORC, when building UHD from source, you should see
"ORC" as one of the configured UHD components.
-- ######################################################
-- # UHD enabled components
-- ######################################################
-- * LibUHD
<cut for brevity>
-- * ORC
\subsubsection x3x0cfg_hostpc_volk_volk Compiling GNURadio with Volk
If you are using GNURadio to build applications, you should compile
GNURadio with Volk. For instructions on how to do this,
<a href="http://gnuradio.org/redmine/projects/gnuradio/wiki/Volk">refer to the GNURadio wiki</a>.
\section x3x0cfg_hosthw Host PC Hardware Selection
\subsection x3x0cfg_hosthw_mb Motherboard
Testing has shown that some motherboards do not provide enough PCIe bus
bandwidth to support higher sample rates. Motherboards with PCIe 3.0 are
required and the PCIe architecture of the motherboard should be
carefully considered. Slots with dedicated PCIe lanes should be used for
PCIe or 10GbE cards that will be connected to the X3x0 device.
\subsection x3x0cfg_hosthw_10gige 10GbE NIC
Intel or Myricom 10GbE NICs are recommended. Mellanox, SolarFlare, and
Chelsio 10GbE NICs are not currently recommended. The Ethernet card
should be plugged into the slot that has the most direct connection with
the CPU (PCIe lanes are not shared with another slot). Refer to the
motherboard manual for more information on PCIe architecture.
\section x3x0cfg_hosthw_troubleshooting Troubleshooting Performance Issues
The output on the host console provides indicators of performance issues
in the form of single upper-case letters. The following table lists the
letters, their meanings, and possible causes:
Indicator |Meaning | Possible Causes
-----------|----------------------|---------------------------------------------------------------------------------
O |Overflow on RX |- Data is not being consumed by user's application fast enough.<br>- CPU governor or other power management not configured correctly.
D |Dropped packet on RX |- Network hardware failure. (Check host NIC, cable, switch, etc...)<br>- PCIe bus on host cannot sustain throughput. (Check ethtool -S \<interface\>).<br>- CPU governor or other power management not configured correctly.<br>- Frame size might not work with the current NIC's MTU.
U |Underflow on TX |- Samples are not being produced by user's application fast enough.<br>- CPU governor or other power management not configured correctly.
L |Late packet (usually on MIMO TX)|- Samples are not being produced by user's application fast enough.<br>- CPU governor or other power management not configured correctly.<br>- Incorrect/invalid time_spec provided.
S |Sequence error on TX |- Network hardware failure. (Check host NIC, cable, switch, etc...)<br>- Frame size might not work with the current NIC's MTU.
\subsection x3x0cfg_hosthw_troubleshooting_eth Troubleshooting Ethernet Issues
1. First, check `ifconfig <interface>` to see if there are any errors
reported on the interface. If there are errors, it is most likely a
network hardware problem.
2. Next, check the output of `ethtool -S <interface>`. The output is
driver-specific, but may give important clues as to what may be
happening. For example, a high value on rx_missed_errors for an
Intel NIC indicates that the bus (i.e. PCIe) is not keeping up.
3. Finally, Wireshark can be used to validate the traffic between the
host and device and make sure there is no unwanted traffic on the
interface.
*/
// vim:ft=doxygen:
|
