Messages in this thread | | | Date | Tue, 11 Oct 2011 10:24:31 -0600 | From | Chris Friesen <> | Subject | Re: big picture UDP/IP performance question re 2.6.18 -> 2.6.32 |
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On 10/06/2011 11:40 PM, Eric Dumazet wrote: > Le jeudi 06 octobre 2011 à 23:27 -0400, starlight@binnacle.cx a écrit :
>> If the older kernels are switching to NAPI >> for much of surge and the switching out >> once the pulse falls off, it might >> conceivably result in much better latency >> and overall performance.
> Thats exactly the opposite : Your old kernel is not fast enough to > enter/exit NAPI on every incoming frame. > > Instead of one IRQ per incoming frame, you have less interrupts : > A napi run processes more than 1 frame. > > Now increase your incoming rate, and you'll discover a new kernel will > be able to process more frames without losses.
I wonder if it would make sense to adjust the interrupt mitigation parameters in the NIC to allow it to accumulate a few packets before interrupting the CPU. We had good luck using this to reduce interrupt rate on a quasi-pathological case where we were bouncing in and out of NAPI because we were *just* fast enough to keep up with incoming packets.
Chris
-- Chris Friesen Software Developer GENBAND chris.friesen@genband.com www.genband.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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