Breno Leitao wrote: > Hello, > > I've perceived that there is a performance issue when running netperf > against 4 e1000 links connected end-to-end to another machine with 4 > e1000 interfaces. > > I have 2 4-port interfaces on my machine, but the test is just > considering 2 port for each interfaces card. > > When I run netperf in just one interface, I get 940.95 * 10^6 bits/sec > of transfer rate. If I run 4 netperf against 4 different interfaces, I > get around 720 * 10^6 bits/sec. <snip>
I take it that's the average for individual interfaces, not the aggregate? RX processing for multi-gigabits per second can be quite expensive. This can be mitigated by interrupt moderation and NAPI polling, jumbo frames (MTU >1500) and/or Large Receive Offload (LRO). I don't think e1000 hardware does LRO, but the driver could presumably be changed use Linux's software LRO. Even with these optimisations, if all RX processing is done on a single CPU this can become a bottleneck. Does the test system have multiple CPUs? Are IRQs for the multiple NICs balanced across multiple CPUs? Ben. -- Ben Hutchings, Senior Software Engineer, Solarflare Communications Not speaking for my employer; that's the marketing department's job. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
