>That would be one solution, but there are plenty of other ways toachieve reliable timely delivery. An interrupt per packet will resultin a lot more overhead than being able to take a single interrupt > that delivers multiple packets though.
Actually I am experiencing these issues with qemu-kvm not qemu. Today I tried invoking qemu-kvm with -no-kvm option and I did not face any packet delay and retransmission issues. But I think it is because qemu is emulation and it takes lot of time within which the packet arrives at the buffer. Are you aware of any rtl8139 card issues with KVM?