On Wed, 2009-08-19 at 16:50 +0200, Johannes Stezenbach wrote: > Hi, > > 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. > The kernel was an ancient 2.6.20. Which driver is this? Is it possible that it does not use NAPI correctly? > I tried hard, but I couldn't find any performance figures for > comparison. (All performance figures I found refer to 1Gbit > or 10Gbit server type systems.) > > 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'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. I have no recent experience with this sort of system, but checksum offload and scatter/gather DMA support should significantly reduce both CPU and memory bus load. Ben. -- Ben Hutchings, Senior Software Engineer, Solarflare Communications Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked. -- 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
