On Thu, Apr 17, 2008 at 9:13 PM, Bruce Evans <[EMAIL PROTECTED]> wrote: > > So the million dollar question: Do you believe that if I disable > > DEVICE_POLLING and use interrupt driven I/O, I could achieve zero > > packet loss over a 1Gbps link? This is the main issue I need to solve > > (solve means either no its not really achievable without a heavy > > rewrite of the driver OR yes it is with some tuning). If the answer > > is yes, then I have to understand the impact on the system in general. > > I just want to be sure I'm on a viable path through the BGE maze! > > > > I think you can get close enough if the bus and memory and CPU(s) > permit and you don't need to get too close to the theoretical limits.
Thanks again Bruce for the detailed response. Here are my results: Good news: Well after fiddling around with it, it seems if I bump the number of rx_bds to 512, disable polling, and use net.isr.direct=1, bge does not drop packets anymore (as verified by assigning a counter within bge_ticks() when a packet is dropped as read by the hardware registers). What's interesting is that there is also an outOfRxBDs register you can read if you suspect chain starvation which I discovered after looking at the Linux driver's more complete stat structure. Bad news: Packets still get dropped but this time by BPF. It seems I pushed the problem upstream (in terms of the stack). The user land software listening in this instance is using BPF. I guess my next adventure is to understand how much can BPF take before dumping packets due to lack of buffer space - currently net.bpf.bufsize is 1048576 which is the maxbufsize. Is this common place for BPF to drop packets? (forgive me I have not searched the mailing list as I just confirmed these results by instrumenting BPF). Could I raise the maxbufsize and still operate safely? (I do have 8GB on a 64-bit system). Almost but no cigar.... -aps _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "[EMAIL PROTECTED]"