I think some of the issue here as well is the tx_metadata.
For continuous streaming, the first packet ONLY should have startofburst = true… Further packets after the first one should have startofburst = false, cuz they really are not start of burst, they are continuations of the initial burst. Furthermore, for continuous streaming as soon as possible, you should not provide a timespec. If you continually provide a timespec to each packet, it will continually try to send them at time = 0.1, which is not what you want… If you want to start your tx at a specific time, then similar to startofburst, you should only provide a timespec with the first packet, all subsequent packets should not include a timespec. Does that make sense? It can be a bit confusing at first, but after writing a few apps, you will be an expert 😊 From: Jason W Zheng [mailto:jason.w.zh...@aero.org] Sent: Monday, August 14, 2017 4:41 PM To: ROBIN TORTORA <ti...@comcast.net>; mle...@ripnet.com Cc: usrp-users@lists.ettus.com Subject: Re: [USRP-users] Buffer underrun issue with simultaneous transmit and receive on the X310 Hi Robin, Marcus It makes no sense to me, then why changing transmit to be on its own channel (daughtercard) would cause the program to work. // set up TX streams and threads std::thread tx_threads[NUM_CHANNELS]; uhd::tx_streamer::sptr tx_streams[NUM_CHANNELS]; uhd::tx_metadata_t md; md.start_of_burst = true; md.end_of_burst = false; md.has_time_spec = true; md.time_spec = uhd::time_spec_t(0.1); for (int i = 0; i < NUM_CHANNELS; i++){ stream_args.channels = std::vector<size_t>(1,i); //changing this from i to 1 causes it to work for unknown reasons tx_streams[i] = usrp->get_tx_stream(stream_args); //start the thread std::cout << "Starting tx thread " << i << std::endl; tx_threads[i] = std::thread(txTask,tx_buffs[i],tx_streams[i],md); } The relevant line is commented in the above code snippet. When I change the channels arguments for the tx stream_args to be on it's own channel (daughterboard) separate from the receive, the underflows go away. @Marcus, in the code I posted, there is no coordination between the transmit and the receive threads. This is for example purposes. The transmit and receive buffers are independent. The transmit thread buffer is prefilled with 0's and is constantly transmitting 0's. _____ From: ROBIN TORTORA <ti...@comcast.net <mailto:ti...@comcast.net> > Sent: Monday, August 14, 2017 1:06:20 PM To: Jason W Zheng via USRP-users; Jason W Zheng Subject: Re: [USRP-users] Buffer underrun issue with simultaneous transmit and receive on the X310 Willing to bet significant money your tx thread is being put on the physical processor that does not have your NIC card attached to it... Then, all data must go over QPI between processors. NUMA is not good for this. You can experiment with affinity to make sure things are all on the same physical processor as your NIC... We no longer buy multi-processor boxes for issues like this, NUMA is bad... On August 14, 2017 at 2:32 PM Jason W Zheng via USRP-users <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com> > wrote: I'm running on a server with 2 Intel Xeon E5-2650 v4, CPU is listed here: https://ark.intel.com/products/91767/Intel-Xeon-Processor-E5-2650-v4-30M-Cache-2_20-GHz The network card I'm using is the recommended Intel X520-DA2 I also have over 500 gigs of ram, so that is not an issue I don't think my cpu or network card are the issue as when I change my code to receive and transmit on separate channels, it works without any underflows. _____ From: USRP-users <usrp-users-boun...@lists.ettus.com <mailto:usrp-users-boun...@lists.ettus.com> > on behalf of Jason W Zheng via USRP-users <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com> > Sent: Monday, August 14, 2017 11:27:24 AM To: ROBIN TORTORA Cc: usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com> Subject: Re: [USRP-users] Buffer underrun issue with simultaneous transmit and receive on the X310 How should I set the tx metadata? My application will essentially stream continuously. Thanks, Jason _____ From: ROBIN TORTORA <ti...@comcast.net <mailto:ti...@comcast.net> > Sent: Monday, August 14, 2017 11:17:07 AM To: Jason W Zheng via USRP-users; Jason W Zheng Subject: Re: [USRP-users] Buffer underrun issue with simultaneous transmit and receive on the X310 I dont see you setting the tx metadata object members to any values, so you are essentially going to tx with default metadata IF there is a constructor that initializes all the members to a consistent value... On August 14, 2017 at 1:56 PM Jason W Zheng via USRP-users <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com> > wrote: Since I haven't gotten a response in a week, I thought some source code might help. I've removed any buffer dependencies leaving just the receive thread and transmit thread. The receive thread is constant receiving to a buffer, while the transmit thread is constantly transmitting 0s from another buffer. On the x310, when I receive and transmit from the same channel (same daughterboard), I get underflows (U's on the console), no matter what the rate. When I put receive and transmit on separate channels, the U's go away. How do I fix my source code so I can receive and transmit from the same channel without underflows? Thanks, Jason _____ From: USRP-users <usrp-users-boun...@lists.ettus.com <mailto:usrp-users-boun...@lists.ettus.com> > on behalf of Jason W Zheng via USRP-users <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com> > Sent: Monday, August 7, 2017 1:05:05 PM To: usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com> Subject: [USRP-users] Buffer underrun issue with simultaneous transmit and receive on the X310 Hi, I'm building an application where I receive data from the x310, process the data, then transmit it out. I have 3 separate threads running, one for each task. The receive task is constantly receiving data from the x310 at 200MS/s and putting it into a buffer. The process task takes data from the receive buffer, processes it, and puts it into a transmit buffer. The transmit task is constantly transmitting data from the transmit buffer at 12.5 MS/s. I get constant underruns (U's on the console) when I try to receive and transmit from the same channel on the x310. However, when I transmit and receive on separate channels, underruns no longer occur. I would like to figure out a solution to this problem as I want to processes two 200MS/s streams on 1 x310. This problem occurs no matter the sample rates. I've tried lowering the receive rate to 50MS/s (while transmitting 4x the data to balance things out) and there are still constant underruns though at a lower rate. I know processing time is not the issue as I've profiled the time it takes to process, and I have even removed the processing task from the application altogether (receive data to a buffer and do nothing with the data; constantly transmit 0's from the transmit buffer) and the underruns still occur. I'm running on UHD 3.11.0, and the x310 is is configured with basic TX/RX daughterboards and flashed with the XG image for use over two 10 gig ethernet links. Thanks, Jason _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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