Hi I believe that i have found an issue with the nfs version 4.2 client side code. I notice that sometimes read performance over nfs (using tcp protocol) drops down to 20MB/s To bring performance back to normal in this case (5GB/s) I have to manually remount the nfs share. After investigations I believe I that the issue is related to reconnect after a connection failure. I have found an easy way to reproduce the problem: 1. Start a simple read io test using for example ‘fio’ 2. Pull out the network cable 3. Wait a few seconds 4. Reinsert the network cable to restore connection The NFS client will reestablish the connection, however the speed recovers only up to 20MB/s. Before cable pull it was 5 GB/s. Leaving the connection for X time does not change the speed, only stopping IO and remounting restores performance. I can see this issue on the latest Ubuntu 22.04 kernels and also clean vanilla kernel – 5.19.1. NFS server side is using Ubuntu 20.04.4. NFS client is connected directly to server (no switch). Network devices are Mellanox ConnectX-5 cards in ethernet mode. I have also tried the MOFED drivers (latest version 5.7.1) and no luck in case this OFED related. Is this known problem? Or any advice would be appreciated. I can supply logs / debug should this we required Thank you Lukasz
