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Re: [Discuss-gnuradio] Getting one or more Ds after hours of running a G

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] Getting one or more Ds after hours of running a GRC app on Ubuntu
Date: Mon, 02 May 2016 22:58:20 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

On 05/02/2016 10:40 PM, John Shields wrote:
I am using Ubunutu 14.04 LTS with GNURadio and have a USRP N200 with SBXv3. I have been using the aptly-named and highly useful Simple_ra though I believe this is orthogonal to the issues I am seeing.

when I run simple_ra with :

simple_ra --srate 2e6 --freq 848e6 --gain 37 --dcg 10000 --devid uhd=a,type=usrp2,addr=,lo_offset=10e6,subdev=A:0 --longitude 172.570277777 --latitude -43.519444444 --spde

the system runs along happily for several maybe even up to 20 odd hours but, as below, I start to see one or more Ds. In one run of 23 hours, I had 10 Ds and eventually a segmentation fault - not sure if it is coincident with issuing of the final 'D'. Sometimes the D is not accompanied by UHD errors

here is the terminal output from the last run:

linux; GNU C++ version 4.8.4; Boost_105400; UHD_003.010.git-156-g2d68f228

Using Volk machine: avx_64_mmx_orc
gr-osmosdr v0.1.4-72-g164a09fc (0.1.5git) gnuradio
built-in source types: file fcd rtl rtl_tcp uhd hackrf bladerf rfspace airspy redpitaya
-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
-- Detecting internal GPSDO.... Found an internal GPSDO
-- Setting references to the internal GPSDO
-- Using subdev spec 'A:0'.
-- Using LO offset of 1e+07 Hz.
WARNING: Overriding original sample rate of 1e+07 with 2e+06
-- Loaded /home/john/.uhd/cal/rx_iq_cal_v0.2_E2R10Z1XS.csv
UHD Error:
    Control packet attempt 0, sequence number 10594:
    RuntimeError: no control response, possible packet loss

UHD Error:
    Control packet attempt 1, sequence number 10595:
    RuntimeError: no control response, possible packet loss

UHD Error:
    Control packet attempt 2, sequence number 10596:
    RuntimeError: no control response, possible packet loss

UHD Error:
    An unexpected exception was caught in a task loop.
    The task loop will now exit, things may not work.
    RuntimeError: link dead: timeout waiting for control packet ACK

I have a fairly powerful cpu Intel® Core™ i7-2600 CPU @ 3.40GHz × 8, 15.6 GiB of memory and run 64-bit os and have the USRP on it's own subnet and NIC.
Apart from setting:
net.core.rmem_max = 50000000
net.core.wmem_max = 1048576

I have not 'tuned' any os settings. When the application is running, the 8 cores are between 40-50% utilised.

When I restart simple_ra after the error, it runs again fine until it hits an issue n-hours in the future.

Any ideas of how I can narrow down the cause of this?

          Kind Regards,


Do you happen to know what kind of NIC you have?

Also, 2MSPS should not be chewing up much of your CPU--what kind of graphics card do you have? Is this a real, or virtual, machine setup?

There Intel 82579LM is known for dropping packets under certain circumstances that shouldn't cause it to drop packets. This is basically fatal to the way UHD does network I/O--since it uses UDP, with no retry mechanism (and, indeed, it's easy to see that at higher sample rates in particular, any TCP-like mechanism is going to cause heartburn for real-time flows).

If you do a:

lspci -v

It should show you what the Ethernet interface(s) are.

If this is a *server* motherboard, the underlying graphics subsystem may be just a framebuffer, in which case, your CPU is working really
  hard to render even simple graphics.

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