On Thu, 26 Apr 2018 22:26:36 +0000 "Wu, Xiaoban" <[email protected]> wrote:
> Dear All, > > > I have two Dell PowerEdge R740 servers A and B running with ubuntu 16.04, > each one has a Mellanox MCX556A-ECAT NIC installed on the PCIe x16 slot. And, > the two NICs are directly connected back to back with a copper cable. > > > On server A, it runs a RX program which runs a function to process and > analyze the received packets. On server B, it runs a packet-gen program which > generates and sends packets out. They are both compiled with dpdk-17.11 > > > Now the interesting thing is that on server B, it is kind of smart and > considerate enough to automatically adjust its TX throughput according to how > fast server A processes the packets. If server A processes the packets > faster, then server B sends packets with a higher throughput. Similarly, if > server A processes the packets slower, then server B sends packets with a > lower throughput. Please note that once the program on server B starts, it is > never interrupted by any way. > > > However, I think the server B should send out the packets with a constant > throughput no matter how fast server A processes the packets. > > > Does anybody else notice this interesting behavior of MLX5 driver? Can > anybody help me disable this feature permanently? Thanks very much for your > help. > > > Best wishes, > > Xiaoban Turn off Ethernet flow control. It was a design mistake that NIC vendors always seem to like because it gives 0 loss benchmarks.
