Hi I see severe network performance degradation with the kernels 4.12-rc1 and 4.12-rc2 in the network virtio driver. Download rate drops down to about 100kB/s.
I bisected it and it is caused by patch
d85b758f72b05a774045545f24d70980e3e9aac4 ("virtio_net: fix support for
small rings"). When I revert this patch, the problem goes away.
The host is Debian Jessie with kernel 4.4.62, the guest is Debian Sid with
kernel 4.12-rc.
Mikulas
