Linas Vepstas <[EMAIL PROTECTED]> wrote:
> 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.
Possible solution / possible brainfart:
Introduce a timer, but don't start to use it to combine packets unless you
receive n packets within the timeframe. If you receive less than m packets
within one timeframe, stop using the timer. The system should now have a
decent response time when the network is idle, and when the network is
busy, nobody will complain about the latency.-)
--
Funny quotes:
22. When everything's going your way, you're in the wrong lane and and going
the wrong way.
Friß, Spammer: [EMAIL PROTECTED] [EMAIL PROTECTED]
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-dev
