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Date: Fri, 24 Aug 2007 08:37:03 -0700 From: akepner@....com To: Jan-Bernd Themann <ossthema@...ibm.com> Cc: netdev <netdev@...r.kernel.org>, Christoph Raisch <raisch@...ibm.com>, Jan-Bernd Themann <themann@...ibm.com>, linux-kernel <linux-kernel@...r.kernel.org>, linux-ppc <linuxppc-dev@...abs.org>, Marcus Eder <meder@...ibm.com>, Thomas Klein <tklein@...ibm.com>, Stefan Roscher <stefan.roscher@...ibm.com> Subject: Re: RFC: issues concerning the next NAPI interface 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. What we need would be some sort of timer polling mode > which will schedule a device after a certain amount of time for high load > situations. With high precision timers this could work well. Current > usual timers are too slow. A finer granularity would be needed to keep the > latency down (and queue length moderate). > We found the same on ia64-sn systems with tg3 a couple of years ago. Using simple interrupt coalescing ("don't interrupt until you've received N packets or M usecs have elapsed") worked reasonably well in practice. If your h/w supports that (and I'd guess it does, since it's such a simple thing), you might try it. -- Arthur - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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