Jonathon, I'm using 1GigE and running at 2Msps (and lower). Unfortunately I cannot use jumbo frames (9000 mtu) as currently our x310's are on a network not setup for them (which breaks other things if enabled). The weird thing is the underruns only occur with the 4 rfnoc radio blocks, they don't occur if I use a usrp source + sink each with 2 channels. I imagine there must be some difference in how the data is passed in these two scenarios? Ideally I would be able to change the dma fifo size directly in the usrp sink block, however as a workaround, I'm trying to build my own fpga image with a different default size for the dram tx fifo and hopefully then I can use the usrp source/sink blocks again.
The underruns don't happen with only 1 TX radio (assuming you use a usrp sink or a rfnoc radio + dma fifo). thanks, Michael On Jul 26, 2017 12:24 PM, "Jonathon Pendlum" <jonathon.pend...@ettus.com> wrote: Hi Mike, Make sure your MTU is set to 9000. Are you using 1GigE or 10GigE? Do you see underruns improve when running with only 1 TX radio? Jonathon On Tue, Jul 25, 2017 at 2:18 PM, Michael Carosino via USRP-users < usrp-users@lists.ettus.com> wrote: > Hi, > > I'm using gnuradio 3.7.12 and rfnoc-devel commit 1908672. > > I'm trying to use both daughter boards on the x310 each at full duplex > (that is, I will have 2 independent tx paths and 2 independent rx paths). > So far I have accomplished this by using the UHD: USRP Sink/Source blocks > and setting them to 2 channels, selecting the appropriate antennas, and > specifying a subdev spec of A:0 B:0. The flowgraph works perfectly sending > and receiving 2 sets of data simultaneously. > > However, I need to have the same capability when using the RFNoC blocks. > I've attempted to use 2 RFNoC radio blocks, one set to Tx, 2 channels, and > the other set to Rx, 2 channels, however the block's parameters have only a > radio select of A or B unlike the usrp source's subdev spec, so this setup > does not appear to work no matter what configurations I try. Am I mistaken > about what the 2 channels refers to here? > > I did finally get an RFNoC setup that works by using 4 RFNoC radio blocks > (2 for transmit with radio select A, B respectively, and 2 for receive with > radio select A, B respectively). However, with this setup I get tons of > underflow "U" in the console. Curiously this happens even when using the > DMAFIFO as ettus recommends so I'm not sure what's going on. My flowgraph > is attached showing this setup. > > (A quick note on why I want to use the rfnoc blocks, apparently the uhd > usrp sink block now automatically includes a DMAFIFO in the tx chain to > deal with the underflow issue caused by tcp flow control, however for my > application the depth/size of this fifo is much too large and causing > massive delays, I've found that by reducing the depth I can minimize my > delay and I'll only get underflows on flowgraph startup which I assume is > due to the tcp slow start phase before backoff occurs. All this to say, if > there is a way to adjust the dma fifo depth from the usrp sink blocks I'd > gladly use that instead). > > > Thanks, > Mike > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > >
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