On Thu, Jan 20, 2022 at 02:51:40PM +0800, Guangguan Wang wrote: >This implement rq flow control in smc-r link layer. QPs >communicating without rq flow control, in the previous >version, may result in RNR (reveive not ready) error, which >means when sq sends a message to the remote qp, but the >remote qp's rq has no valid rq entities to receive the message. >In RNR condition, the rdma transport layer may retransmit >the messages again and again until the rq has any entities, >which may lower the performance, especially in heavy traffic. >Using credits to do rq flow control can avoid the occurrence >of RNR. I'm wondering if SRQ can be used to solve this problem ? One of my concern on credit-base flow control is if the RTT is a bit longer, we may have to wait RTT/2 for peer to grant us credit before we can really send more data. That may decrease the maximium bandwidth we can achive in this case.
