netdev - Re: GSO/GRO and UDP performance

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Message-ID: <1378295631.7360.98.camel@edumazet-glaptop>
Date:	Wed, 04 Sep 2013 04:53:51 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	James Yonan <james@...nvpn.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: GSO/GRO and UDP performance

On Wed, 2013-09-04 at 04:07 -0600, James Yonan wrote:

> The bundle of UDP packets would traverse the stack as a unit until it 
> reaches the socket layer, where recvmmsg could pass the whole bundle up 
> to userspace in a single transaction (or recvmsg could disaggregate the 
> bundle and pass each datagram individually).

That would require a lot of work, say in netfilter, but also in core
network stack in forwarding, and all UDP users (L2TP, vxlan).

Very unlikely to happen IMHO.

I suspect the performance is coming from aggregation done in user space,
then re-injected into the kernel ?

You could use a kernel module, using udp_encap_enable() and friends.

Check vxlan_socket_create() for an example



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