On Mon, Feb 28, 2011 at 12:49:01PM +0100, Manuel Guesdon wrote: > OK. Anyway NIC buffers restrict buffered packets number. But the problem > remain: why a (for exemple) dual Xeon E5520@2.27GHz with Intel PRO/1000 > (82576) can't route 150kpps without Ierr :-) > http://www.oxymium.net/tmp/core3-dmesg
I've done some more comprehensive testing and talked to some other developers, and it seems that 150kpps is in the range of what is expected for such hardware with an unoptimized install. One thing that seems to have a big performance impact is net.inet.ip.ifq.maxlen. If and only if your network cards are all supported by MCLGETI (ie, they show LWM/CWM/HWM values in 'systat mbufs', you can try increasing ifq.maxlen until you don't see net.inet.ip.ifq.drops incrementing anymore under constant load. On my test box here - Intel(R) Xeon(R) CPU 5140 @ 2.33GHz with em(4), pf disabled - increasing net.inet.ip.ifq.maxlen to 8192 gets more than double the performance compared with the default of 256. We're looking at making the ifq.maxlen tune itself so you don't have to twiddle this knob anymore, not sure if and when that will happen though.
