netdev - Re: [PATCH RFC 3/3] udp: Support UDP fraglist GRO/GSO.

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Date:   Sat, 26 Jan 2019 10:36:40 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>
Cc:     netdev@...r.kernel.org, Willem de Bruijn <willemb@...gle.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>
Subject: Re: [PATCH RFC 3/3] udp: Support UDP fraglist GRO/GSO.

On Fri, 2019-01-25 at 08:58 +0100, Steffen Klassert wrote:
> > Finally this will cause GRO/GSO for local UDP packets delivery to non
> > GSO_SEGMENT sockets. That could be possibly a win or a regression: we
> > save on netfilter/IP stack traversal, but we add additional work, some
> > performances figures would probably help.
> 
> I did some tests for the local receive path with netperf and iperf, but
> in this case the sender that generates the packets is the bottleneck.
> So the benchmarks are not that meaningful for the receive path.

I think we can use GSO on the sender if we add some additional code on
the rx side - for testing purpose only - limiting the GRO aggregation
to an (user controlled via sysfs) value.

Beyond that, other options would be using multiple senders threads and
a single rx queue and/or asymmetric CPUs.

> Do you have some performance tests for UDP GRO receive?

I have a bunch of ansible(!!!) scripts I can share, if you dare. They
have a lot of hard-coded setting, so I'm not sure how much can be re-
used outside my testbed.

I also hope/wish/think/ I can allocate some time for benchmarking this
on my own in the next week[s], so I'll try to post some results for the
next iteration.

Cheers,

Paolo