netdev - Re: [PATCH net-next v2 4/4] bonding: balance ICMP echoes in layer3+4 mode

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Date:   Thu, 31 Oct 2019 17:22:21 +0100
From:   Matteo Croce <mcroce@...hat.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        netdev <netdev@...r.kernel.org>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S . Miller" <davem@...emloft.net>,
        Stanislav Fomichev <sdf@...gle.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Song Liu <songliubraving@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Paul Blakey <paulb@...lanox.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v2 4/4] bonding: balance ICMP echoes in layer3+4 mode

On Wed, Oct 30, 2019 at 12:19 AM Matteo Croce <mcroce@...hat.com> wrote:
>
> On Wed, Oct 30, 2019 at 12:14 AM Eric Dumazet <eric.dumazet@...il.com> wrote:
> >
> >
> >
> > On 10/29/19 4:03 PM, Matteo Croce wrote:
> >
> > > Hi Eric,
> > >
> > > this would work for locally generated echoes, but what about forwarded packets?
> > > The point behind my changeset is to provide consistent results within
> > > a session by using the same path for request and response,
> > > but avoid all sessions flowing to the same path.
> > > This should resemble what happens with TCP and UDP: different
> > > connections, different port, probably a different path. And by doing
> > > this in the flow dissector, other applications could benefit it.
> >
> > In principle it is fine, but I was not sure of overall impact of your change
> > on performance for 99.9% of packets that are not ICMP :)
> >
>
> Good point. I didn't measure it (I will) but all the code additions
> are under some if (proto == ICMP) or similar.
> My guess is that performance shouldn't change for non ICMP traffic,
> but I'm curious to test it.
>

Indeed if there is some impact it's way below the measurement uncertainty.
I've bonded two veth pairs and added a tc drop to the peers, then
started mausezahn to generate UDP traffic.
Traffic is measured on the veth peers:

Stock 5.4-rc5:

rx: 261.5 Mbps 605.4 Kpps
rx: 261.2 Mbps 604.6 Kpps
rx: 261.6 Mbps 605.5 Kpps

patched:

rx: 261.4 Mbps 605.1 Kpps
rx: 261.1 Mbps 604.4 Kpps
rx: 260.3 Mbps 602.5 Kpps

perf top shows no significatn change in bond* and skb_flow* functions

Regards,
-- 
Matteo Croce
per aspera ad upstream