Re: [RFC PATCH] udp: allow busy_poll on some unconnected sockets

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On Thu, 2014-04-10 at 19:38 +0100, Edward Cree wrote:
> On 10/04/14 19:32, Eric Dumazet wrote:
> > On Thu, 2014-04-10 at 19:04 +0100, Edward Cree wrote:
> >
> >> Tested by setting IFF_SINGLE_NAPI in sfc; a UDP ping-pong test showed a
> >>  performance benefit from sysctl net.core.busy_{read,poll}=50 in both the
> >>  connected and unconnected case, where previously it only saw the benefit
> >>  when the socket had been connected.
> > Right, but how often do we have single NAPI devices on hosts wanting
> > very low latencies ?
> >
> Well, sfc only has a single NAPI context per device, and I'm fairly sure
> most sfc users want very low latencies.
> Or have I misunderstood?

sfc is multi queue/channel, but has a single NAPI instance ?

Sounds wierd.

Please explain me, how GRO can be efficient.

I believe you have one napi per channel.



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