Johannes Stezenbach wrote: > a while ago I was working on a SoC with 200MHz ARM926EJ-S CPU > and integrated 100Mbit ethernet core, connected on internal > (fast) memory bus, with DMA. With iperf I measured: > > TCP RX ~70Mbit/sec (iperf -s on SoC, iperf -c on destop PC) > TCP TX ~56Mbit/sec (iperf -s on destop PC, iperf -c o SoC) > > The CPU load during the iperf test is around > 1% user, 44% system, 4% irq, 48% softirq, with 7500 irqs/sec. > > The kernel used in these measurements does not have iptables > support, I think packet filtering will slow it down noticably, > but I didn't actually try. The ethernet driver uses NAPI, > but it doesn't seem to be a win judging from the irq/sec number. You should see far fewer interrupts if NAPI was working properly. Rather than NAPI not being a win, it looks like it's not active at all. 7500/sec is close to the packet rate, for sending TCP with full-size ethernet packages over a 100Mbit ethernet link. > What I'm interested in are some numbers for similar hardware, > to find out if my hardware and/or ethernet driver can be improved, > or if the CPU will always be the limiting factor. I have a SoC with a 166MHz ARMv4 (ARM7TDMI I think, but I'm not sure), and an external RTL8139 100Mbit ethernet chip over the SoC's PCI bus. It gets a little over 80Mbit/s actual data throughput in both directions, running a simple FTP client. > I'd also be interested to know if hardware checksumming > support would improve throughput noticably in such a system, > or if it is only useful for 1Gbit and above. > > Did anyone actually manage to get close to 100Mbit/sec > with similar CPU resources? Remember, the TCP throughput cannot reach 100Mbit/sec due to the overhead of packet framing. But it should be much closer to 100 than 70. -- Jamie -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
