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

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Date:   Thu, 08 Dec 2016 19:50:08 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Tom Herbert <tom@...bertland.com>
Subject: Re: [PATCH net-next] net: sock_rps_record_flow() is for connected
 sockets

On Wed, 2016-12-07 at 06:29 -0800, Eric Dumazet wrote:
> On Wed, 2016-12-07 at 08:57 +0100, Paolo Abeni wrote:
> 
> > We have some experimental patches to implement GRO for plain UDP
> > connected sockets, using frag_list to preserve the individual skb len,
> > and deliver the packet to user space individually. With that I got
> > ~3mpps with a single queue/user space sink - before the recent udp
> > improvements. I would like to present these patches on netdev soon (no
> > sooner than next week, anyway).
> > 
> 
> Make sure you handle properly all netfilter helpers :(

Thank you for the head-up! 
UDP-GRO will be enabled by a specific netdev feature bit, disabled by
default, should not impact by default any setup.

> Keeping frag_list means you keep one sk_buff per segment, so this really
> looks like a legacy UDP server (like a DNS server) wont benefit from
> this anyway.

I'm sorry, I do not follow.

UDP GRO will require connected socket - very likely no DNS server. The
use-case is an application using long lived UDP sockets doing a lot of
traffic, like fix protocol feeds over UDP. 

Thank you,

Paolo