Not a typo & yes quite likely. I haven't tuned nbd/vsock at all. Edit: I patched both ends to change SO_SNDBUF and SO_RCVBUF from the default (both 212992) to

Not a typo & yes quite likely. I haven't tuned nbd/vsock at all. Edit: I patched both ends to change SO_SNDBUF and SO_RCVBUF from the default (both 212992) to 4194304, and that made no difference.