Re: [Discuss-gnuradio] UHD Performance: Reaching 8Msps TX with USB 2.0 (?)

[Vincenzo Pellegrini]

Hi Nick, thanks for the suggestions.

I will test the args. What is the best (maximum?) possible value for the send_frame_size in order to minimize the overhead yielded by UHD?

Would it be correct to assume that the over-the-wire overhead yielded by UHD is larger than what the classic libusrp used to impose? If yes, by what scale?

The USB peripherals configuration does not differ when I use the classic libusrp version and the UHD. Also, the difference in terms of underflow amount when using the tx_samples_from_file (UHD) and an equivalent classic, libusrp-based utility is huge using the same USB controller, same hard drive, same OS (fedora 16) in both cases. Actually I'm using the very same machine to do the tests.

A friend of mine here in Pisa (Mario di Dio, he's also on the list) has obtained the same results on both Ubuntu 11.10 and Fedora 14. He had almost no underruns apart from some at the very beginning when he used his USB 3.0 port and lots of underruns when using the 2.0 USBs of the same laptop.

I think I'm seeing something macroscopic, maybe a macroscopic mistake of mine. May I know what version of UHD you are using and your OS?  

sorry for the many questions, I'm just trying to figure out what I might be missing in order to properly use UHD for my purposes.

thanks

Il giorno 21 marzo 2012 19:59, Nick Foster <address@hidden> ha scritto:

On Wed, Mar 21, 2012 at 11:42 AM, Vincenzo Pellegrini <address@hidden> wrote:

HI fellows,

I was wondering if anybody has been trying to reach 8 Complex Msps over the USB 2.0 on the Tx path.

While this has always been OK with old libusrp (and USRP 1) it appears to be no longer possible by means of UHD

neither when trying to do that on USRP1 (a few underruns) nor on B100 (lots of overruns). 

Everything appears instead fine on the Rx path

Is there any workaround to this? 

..or did I miss something?

thanks everybody

PS

USB 3.0 seems to be capable enough for the 8 Msps.

Is USB3.0 a requirement for 8 Msps on the B100?

Look for other devices on that USB bus using lsusb. Avoid sharing the bus with other peripherals (bluetooth, wlan, etc). You can also modify the transport parameters using --args=recv_frame_size=xxxxx,send_frame_size=xxxxx. This will give you the same control over receive & send frame size that the old USRP1 drivers had. The default receive/send frame sizes are 16K, which seems to work OK on most machines.

For comparison, the USB host controller I'm using is the Intel 6 Series/C200, and on B100 I can use a TX send rate of 10.67Msps without underflow, although occasionally underflows occur at the very beginning of the transmission (likely due to interrupt coalescing on the USB controller).

I also have a USB 3.0 controller (an NEC Corporation uPD720200) on this laptop, which fares more poorly, but still easily achieves 8Msps. I don't have a good explanation as to why some USB controllers do better than others. USB 3.0 is certainly not required on B100/USRP1, as neither device uses USB 3.0.

--n

 

____________________________________________________________B100

./benchmark_rate --tx_rate 8e6

linux; GNU C++ version 4.6.1 20110908 (Red Hat 4.6.1-9); Boost_104600; UHD_003.004.000-325-g7e296167

Creating the usrp device with: ...

-- USRP-B100 clock control: 10

--   r_counter: 2

--   a_counter: 0

--   b_counter: 20

--   prescaler: 8

--   vco_divider: 5

--   chan_divider: 5

--   vco_rate: 1600.000000MHz

--   chan_rate: 320.000000MHz

--   out_rate: 64.000000MHz

-- 

Using Device: Single USRP:

  Device: B-Series Device

  Mboard 0: B100 (B-Hundo)

  RX Channel: 0

    RX DSP: 0

    RX Dboard: A

    RX Subdev: WBX RX v3 + Simple GDB

  TX Channel: 0

    TX DSP: 0

    TX Dboard: A

    TX Subdev: WBX TX v3 + Simple GDB

Testing transmit rate 8.000000 Msps

UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU

Benchmark rate summary:

  Num received samples:    0

  Num dropped samples:     0

  Num overflows detected:  0

  Num transmitted samples: 79931260

  Num sequence errors:     0

  Num underflows detected: 406

Done!

 

./benchmark_rate --tx_rate 8e6 --tx_otw sc16 

linux; GNU C++ version 4.6.1 20110908 (Red Hat 4.6.1-9); Boost_104600; UHD_003.004.000-325-g7e296167

Creating the usrp device with: ...

-- USRP-B100 clock control: 10

--   r_counter: 2

--   a_counter: 0

--   b_counter: 20

--   prescaler: 8

--   vco_divider: 5

--   chan_divider: 5

--   vco_rate: 1600.000000MHz

--   chan_rate: 320.000000MHz

--   out_rate: 64.000000MHz

-- 

Using Device: Single USRP:

  Device: B-Series Device

  Mboard 0: B100 (B-Hundo)

  RX Channel: 0

    RX DSP: 0

    RX Dboard: A

    RX Subdev: WBX RX v3 + Simple GDB

  TX Channel: 0

    TX DSP: 0

    TX Dboard: A

    TX Subdev: WBX TX v3 + Simple GDB

Testing transmit rate 8.000000 Msps

UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU

Benchmark rate summary:

  Num received samples:    0

  Num dropped samples:     0

  Num overflows detected:  0

  Num transmitted samples: 79890620

  Num sequence errors:     0

  Num underflows detected: 696

Done!

____________________________________________________________USRP 1

./benchmark_rate --tx_rate 8e6 --tx_otw sc16 

linux; GNU C++ version 4.6.1 20110908 (Red Hat 4.6.1-9); Boost_104600; UHD_003.004.000-325-g7e296167

*** Warning! ***

Benchmark results will be inaccurate on USRP1 due to insufficient features.

Creating the usrp device with: ...

-- Opening a USRP1 device...

-- Using FPGA clock rate of 64.000000MHz...

Using Device: Single USRP:

  Device: USRP1 Device

  Mboard 0: USRP1 (Classic)

  RX Channel: 0

    RX DSP: 0

    RX Dboard: B

    RX Subdev: WBX RX v2 + Simple GDB

  TX Channel: 0

    TX DSP: 0

    TX Dboard: B

    TX Subdev: WBX TX v2 + Simple GDB

Testing transmit rate 8.000000 Msps

UUUUU

Benchmark rate summary:

  Num received samples:    0

  Num dropped samples:     0

  Num overflows detected:  0

  Num transmitted samples: 80022656

  Num sequence errors:     0

  Num underflows detected: 5

Done!

____________________________________________________________everything fine with 8bit samples

./benchmark_rate --tx_rate 8e6 --tx_otw sc8

linux; GNU C++ version 4.6.1 20110908 (Red Hat 4.6.1-9); Boost_104600; UHD_003.004.000-325-g7e296167

-- Loading firmware image: /usr/share/uhd/images/usrp_b100_fw.ihx... done

Creating the usrp device with: ...

-- USRP-B100 clock control: 10

--   r_counter: 2

--   a_counter: 0

--   b_counter: 20

--   prescaler: 8

--   vco_divider: 5

--   chan_divider: 5

--   vco_rate: 1600.000000MHz

--   chan_rate: 320.000000MHz

--   out_rate: 64.000000MHz

-- 

-- Loading FPGA image: /usr/share/uhd/images/usrp_b100_fpga.bin... done

Using Device: Single USRP:

  Device: B-Series Device

  Mboard 0: B100 (B-Hundo)

  RX Channel: 0

    RX DSP: 0

    RX Dboard: A

    RX Subdev: WBX RX v3 + Simple GDB

  TX Channel: 0

    TX DSP: 0

    TX Dboard: A

    TX Subdev: WBX TX v3 + Simple GDB

Testing transmit rate 8.000000 Msps

Benchmark rate summary:

  Num received samples:    0

  Num dropped samples:     0

  Num overflows detected:  0

  Num transmitted samples: 80053688

  Num sequence errors:     0

  Num underflows detected: 0

Done!

--
Vincenzo Pellegrini
http://www.youtube.com/user/wwvince1

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--
Vincenzo Pellegrini
http://www.youtube.com/user/wwvince1