netdev - Re: [PATCH net-next] net: sock_rps_record

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Date:   Thu, 8 Dec 2016 11:15:37 -0800
From:   Tom Herbert <tom@...bertland.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Paolo Abeni <pabeni@...hat.com>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net-next] net: sock_rps_record_flow() is for connected sockets

On Thu, Dec 8, 2016 at 10:02 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2016-12-08 at 09:49 -0800, Tom Herbert wrote:
>
>> Of course that would only help on systems where no one enable encaps,
>> ie. looks good in the the simple benchmarks but in real life if just
>> one socket enables encap everyone else takes the hit. Alternatively,
>> maybe we could do early demux when we do the lookup in GRO to
>> eliminate the extra lookup?
>
> Well, if you do the lookup in GRO, wont it be done for every incoming
> MSS, instead of once per GRO packet ?

We should be able to avoid that. We already do the lookup for every
UDP packet going into GRO, would only need to take the refcnt once for
the whole GRO packet.

>
> Anyway, the flooded UDP sockets out there are not normally connected

We still should be able to use early demux in that case, just can't
avoid the route lookup. I wonder if we might be able to cache a soft
route maybe for the last local destination received to help the
unconnected sockets case...

In any case, I can take a look at of doing early demux from with UDP GRO.

Tom

> ones.
>
>
>