Hey, On 2/25/2019 11:05 AM, Garegin Grigoryan (RIT Student) wrote: > Hi, > > I'm new to RDMA and trying to understand rping.c > (https://github.com/ofiwg/librdmacm/blob/master/examples/rping.c) > code. You should be looking at the latest rdma-core repo at: https://github.com/linux-rdma/rdma-core > I have three questions so far. > 1. What is the fundamental difference between cb->rdma_buf and > cb->start_buf? Why rdma_buf is needed at all? Nothing other than the "ping source" data originates, at the rping client, from start_buf and the "pingponged" data lands in rdma_buf at the client. It might help to think of rping as a "test tool" that implements a traditional "icmp ping" over and RDMA connection. And, it is designed to utilize all the main rdma operations: SEND, RECV, READ, and WRITE operations. So it is not optimized in any way other than to exercise these features of rdma. > 2. Does rping_format_send just print out the message to-be-sent? It adds the buffer virtual address, the rkey, and length to the SEND message that is sent to the server for this rping "iteration". The server uses that address, rkey, and length to post and RDMA READ to pull the "ping" data from the client to the server. The fact that these values don't change between iterations irrelevant. The rping wire protocol assumes the client sends this information to the server for every "ping" iteration. Note this comment at the front of rping.c: /* * rping "ping/pong" loop: * client sends source rkey/addr/len * server receives source rkey/add/len * server rdma reads "ping" data from source * server sends "go ahead" on rdma read completion * client sends sink rkey/addr/len * server receives sink rkey/addr/len * server rdma writes "pong" data to sink * server sends "go ahead" on rdma write completion * <repeat loop> */ > 3. Line 980 is same as 964. Does it post the same message to the send > queue? I can not find if there have been any changes to cb->sq_wr > between 964 and 980. I'm not sure which lines you are referring to. Pleaes cite the latest rdma-core repo code, and include the src code snipit to ask specific questions... > Thank you. > -- > Sincerely, > Garegin Grigoryan
