Bug 216425

Summary:	When transfer large files, NFS hangs when VM network card is if_vmx or if_vxn, ok for e1000
Product:	Base System	Reporter:	patdung100
Component:	kern	Assignee:	freebsd-fs (Nobody) <fs>
Status:	New ---
Severity:	Affects Only Me
Priority:	---
Version:	11.0-STABLE
Hardware:	amd64
OS:	Any

Description patdung100 2017-01-24 11:40:18 UTC

Setup: FreeBSD VM guest as NFS server. The physical host running VMware workstation.

FreeBSD version: FreeBSD 11.0-STABLE #0 r309850: Sun Dec 11 19:30:14
One disk is ZFS, de-duplication and compression is enabled for the ZFS dataset.
It is shared out for NFS to another client (The host is Linux)

When the NIC setting of the VM is vmxnet3 (if_vmx) or vmxnet (if_vxn):
After the client had mount the NFS, the client side would hang if there are large file operations such as 'dd if=/dev/zero of=/nfs_mount_point/file bs=100M count=1' or copy large files to the NFS mount point.

When it had problem. The CPU usage in FreeBSD is normal. There would be serious packet loss for all the NICs in the FreeBSD VM guest. Besides packet loss, for the other NFS Linux clients, they will see these error message:
[ 5843.755544] nfs: server FreeBSD_SERVER_IP not responding, timed out

After changing the emulated ethernet card to e1000. It is fine but the speed is slower (10 gigabit vs 1 gigabit).

I have tested with other Linux guests, they do not have such problem.