Thanks!
Sorry for the wrong link.
Here's the code I am asking about in the question number 3. What is
the difference between these two parts and why do we need to post to
the send queue twice?
static int rping_test_client(struct rping_cb *cb){
........
rping_format_send(cb, cb->start_buf, cb->start_mr);
ret = ibv_post_send(cb->qp, &cb->sq_wr, &bad_wr);
.......
rping_format_send(cb, cb->rdma_buf, cb->rdma_mr);
ret = ibv_post_send(cb->qp, &cb->sq_wr, &bad_wr);
.......
}
On Mon, Feb 25, 2019 at 2:41 PM Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx> wrote:
>
> 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
--
Sincerely,
Garegin Grigoryan
