TCP Segmentation Offload (TSO) Performance On HP rp4440 Servers Using PCI-X 2-Port Gigabit Ethernet Cards

Throughput: Faster = Better
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Throughput: Faster = Better
Figure 3 rp4440 Throughput with GigE and TSO
Figure 3 shows transmit and bidirectional throughput results on the rp4440 over GigE
both without and with TSO. In the enclosed graph, the Gigabit Ethernet throughput numbers
are shown in Megabits per second. In this test, the higher the throughput number, the better!
• For bidirectional traffic, TSO increases throughput much more with multiple ports.
The actual throughput increases are:
for 1 port with TSO on, 3.95 Mbit/s more throughput ,
for 2-ports with TSO on, 178.63 Mbit/s more throughput , and
for 4 ports, 577.18 Mbit/s more throughput than when TSO is off!
• TSO does not significantly affect transmit only throughput because the ports are
already at link rate.
TSO increases the throughput of bidirectional traffic on iether-based GigE cards especially
over multiple ports. TSO does not improve throughput on systems that are already nearing
link rate. But, because TSO does free up CPU, it can provide improved throughput for
systems that are CPU-bound or that are not already at or near link rate on all network ports.