Hi Richard, I don't know the answer but I have a couple of comments / questions: 1) do you have cables that would enable you to eliminate your switch (at least for debugging purposes)? I'm thinking of some type of NIC re-config and breakout cable that would allow your NIC to have multiple 10Gbe connections such that you could connect directly to several N310 SFP+ 2) you mentioned that you connected both SFP+ cables to each N310. If you are only using 2 channels, you can get by with only one 10Gbe. I think it is worth a try to re-run your tests without using the "second_addr" parameter such that the 2nd SFP+ port is unused 3) Have you optimized your server with the rmemmax and rx descriptors that are mentioned in the Ettus performance tuning tips? 4) How are you evaluating? If you aren't using benchmark_rate, I would suggest trying this.
On Fri, Feb 4, 2022 at 3:27 PM Richard Bell <[email protected]> wrote: > 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 > _______________________________________________ > USRP-users mailing list -- [email protected] > To unsubscribe send an email to [email protected] >
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