Hi! On 14:31 Tue 21 Apr , Jeffrey Cao wrote: > On Tue, Apr 21, 2009 at 06:49:13AM +0200, Michael Blizek wrote: > > > > > CPU causes problems only when you test with small packets, say 64 bytes > > > packets. Small packets will cause more frequent interrupt for the CPU. > > > If you can pass 24 Mbps with 2k data size, then you at least can pass > > > 24 Mbps with bigger packets. > > > > If you use UDP, the kernel has to fragment and concat big packets on IP layer. > > At least in theory, this can cause CPU usage to increase. > > > > I don't think the package fragement is an issue to cause CPU usage to increase > greatly. That's a simple computation work, I don't think that will cause much > CPU time. What affect greatly is the hardware IRQ caused by each packet arrive > and the soft IRQ for each packet, and the kernel/user space switch. > > If you did some practical network performance test work, you'd have understood > that bigger packet size will cause better througput performance. Only smaller > packets will cause trouble. You are right - small packets are probably way more often the cause of low performance than "oversized" packets. However, I am not talking about transfer of large amounts of data via TCP, but about big UDP packets. They are quite rare and all I said was "At least in theory, this can cause CPU usage to increase". -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
