Re: [PATCH v6 net-next 2/5] net: implement support for low latencysocket polling

[Eliezer Tamir]

On 29/05/2013 22:08, Eric Dumazet wrote:
> On Wed, 2013-05-29 at 21:52 +0300, Or Gerlitz wrote:
> > Eliezer Tamir <eliezer.tamir@xxxxxxxxxxxxxxx> wrote:
> > > Or Gerlitz wrote:
> >
> > > > Unlike with TCP sockets, UDP sockets may receive packets from multiple
> > > > sources and hence the receiving context may be steered to be executed
> > > > on different cores through RSS or other Flow-Steering HW mechanisms
> > > > which could mean different napi contexts for the same socket, is that
> > > > a problem here? what's the severity?
> >
> > > Nothing will break if you poll on the wrong queue.
> > > Your data will come through normal NAPI processing of the right queue.
> >
> > Can you elaborate a little further, why you call this "wrong" and "right"?
> > --
>
> This definitely need some documentation, because before llpoll, device
> RX path was serviced by the cpu receiving the harwdare interrupt.
>
> So the "wrong" queue could add false sharing, and wrong NUMA
> allocations.

Yes,
To work properly when you have more than one NUMA node, you have to have 
packet steering set up, either by your NIC or by HW accelerated RFS.

I would like to add a short writeup of the design and suggested 
configuration. Where should it go?
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