Turning off scatter gather disables the use of fragments in send buffers. So for the xen-netfront driver there is no chance that those fragments end up requiring more than the 19 pages that it can handle in one transaction.
Turning off scatter gather disables the use of fragments in send buffers. So for the xen-netfront driver there is no chance that those fragments end up requiring more than the 19 pages that it can handle in one transaction.