Hello, I know that when I see O's (overruns) in the terminal it means my host processing is not keeping up with the sample stream coming in from the USRP. Samples are being dropped because the host is too slow to keep up.
I'm wondering if there is a test I can run that would reveal the cause of the O's on my server. What is it on my server that is the bottleneck? Do O's mean the problem is buffer overruns within the NIC itself? Does it mean buffer overrun after the CPU? Does it mean buffer overrun while filling up ram? I am using a 2 port QFSP+ 100G NIC with both ports attached via QSFP+ cables to a 100G switch. From the switch I connect 5 USRP n310's using their SFP+ ports and SFP+ cables. Each of the n310's dual SFP+ ports are connected to the 100G switch and in this configuration I am able to use 2 of the 5 n310's simultaneously with 2 receive antennas per radio sampling at 125 MHz without any O's. When I increase the number of radios above this, I start seeing O's. The server is a 64 core machine with 200G RAM. I calculate the total throughput required to keep up with 5 n310's sampling at 125 MHz from 2 antennas with 16 bit I and 16 bit Q coming off the wire at the server as: (5 radios)*(2 antennas)*(125 mega samples per second)*(32 bits per complex sample)=40 Gbit/s or just 5 GByte/s. This is well below the capability of the network and I assume a high end 64 core server, unless I'm overlooking something? Any help or feedback is appreciated. Richard
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