On Fri, Aug 24, 2007 at 03:59:16PM +0200, Jan-Bernd Themann wrote: > 3) On modern systems the incoming packets are processed very fast. Especially > on SMP systems when we use multiple queues we process only a few packets > per napi poll cycle. So NAPI does not work very well here and the > interrupt > rate is still high.
I saw this too, on a system that is "modern" but not terribly fast, and only slightly (2-way) smp. (the spidernet) I experimented wih various solutions, none were terribly exciting. The thing that killed all of them was a crazy test case that someone sprung on me: They had written a worst-case network ping-pong app: send one packet, wait for reply, send one packet, etc. If I waited (indefinitely) for a second packet to show up, the test case completely stalled (since no second packet would ever arrive). And if I introduced a timer to wait for a second packet, then I just increased the latency in the response to the first packet, and this was noticed, and folks complained. In the end, I just let it be, and let the system work as a busy-beaver, with the high interrupt rate. Is this a wise thing to do? I was thinking that, if the system is under heavy load, then the interrupt rate would fall, since (for less pathological network loads) more packets would queue up before the poll was serviced. But I did not actually measure the interrupt rate under heavy load ... --linas - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
