Hi Bálint, You may want to step backwards once more and run the "benchmark_rate" utility with 4 channels with tx & rx rates at 1MHz. This will eliminate the file I/O considerations (both for tx and rx). If benchmark_rate is successful, see how high you can increase the rate. The n4200 is not a very powerful CPU, so you might be significantly limited. If you are using the 1Gb interface, then the max sample rate you can achieve (assuming your CPU is not limiting you) for 4 channels is ~6.25 MS/s because of the 1Gb limit (4 chan x 6.25MS/s x 4 bytes/sample x 8 bits/byte = 800Mb/s).
Once you are satisfied with the USRP streaming rates, you can try putting your tx and rx files in a ram drive in order to improve the file I/O so that it does not impact overall performance appreciably. Then retry txrx_loopback_to_file. Rob On Thu, Sep 3, 2020 at 3:23 AM Bálint Horváth via USRP-users < usrp-users@lists.ettus.com> wrote: > Hello, > > I have a USRP N310 and in my application I want to do a 4 channel > loopback. Transmit sources are files and the received samples are > processed. However, I ran into stability issues receiving a lot of Late > packet errors (LLLLL). To trace the problem I executed the basic UHD > example txrx_loopback_to_file on 4 channels with 1Msamp/sec sample rate. > There every time I got ERROR_CODE_LATE_COMMAND. When I executed it for 3 > channels I got it working, though on some occasions the same error would > occur. With netstat I see that in case I receive the L-s, the UDP packet > error is increasing. > > After reading through the manual and threads I tried several things but > could not resolve the issue. > - I set the net.core.rmem_max and wmem_max as suggested > - I set the MTU on both host and N310 to 8000 (also tried 1500) > - I put the CPU to performance mode with cpupower > > My system config is: > - Ubuntu 20.04, UHD version 3.15, (gnuradio installed with apt) > - quad core intel n4200, 8GB RAM > - N310 is loaded with default HG firmware (sfp0 is 1GBit) > > Do you have any tips on how to resolve this? > > Thanks! > > Balint > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >
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