1

I am trying to send data generated from my FPGA card out to an IB device. I want the latency to be as low as possible, so I am thinking this may be the data path.

FPGA --> DMA via scatter/gather DMA into Memory Buffer --> RDMA into a ConnectX-6 card --> IB cable --> my other device.

With this potential solution, I have a bunch of unknowns that I cant seem to find on the internet and was hoping someone could assist:

  1. Is this possible/viable? I have never worked with DMA and RDMA and want to make sure it can work before purchasing. I fear it may be a one or the other situation and you can't do both or doing both will cause latency somehow or lost data.

  2. Ideally, I want it to reach the other devices CPU (I just want it to avoid the Host device's CPU), but it seems like RDMA makes it avoid both CPUs? Would it then just be DMA to my ConnectX card? I've been searching the datasheets/manuals/firmware/support to see if the ConnectX cards can support DMA, but it doesn't seem to be possible? They just support RDMA (which is a subset of DMA.)

Any information/guidance would be appreciated. If I am in the wrong group, let me know. I wasn't sure if it belonged here or in the electrical engineering one (there seemed to be more DMA/RDMA questions in here)

bchang32
  • 27
  • 3
  • Did you consider posting this question on electronics stackexchange? – quantum231 Apr 08 '21 at 07:07
  • @quantum231 I did but from the search there, there was no topics on that compared to a handful here so I thought here would be more relevant. I'll try there as well then. – bchang32 Apr 08 '21 at 13:40
  • 1
    This question is about DMA and FPGA. It is possible that electronics stackexchange is a better place to ask this type of question. – quantum231 Apr 08 '21 at 14:40
  • RDMA from the FPGA to the IB card via what mechanism? You want to plug Infiniband into the FPGA card? – user253751 Apr 26 '22 at 16:16
  • Many FPGA cards come with IB-compatible (I think) QSFP interfaces. You would get a lot lower latency if you plugged your FPGA card directly into the IP network, bypassing the computer altogether – user253751 Sep 30 '22 at 17:49

0 Answers0