netdev - Re: [PATCH net-next 3/4] vxlan: remove gro

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Date:	Thu, 07 Jul 2016 18:13:22 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Paolo Abeni <pabeni@...hat.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Jesse Gross <jesse@...nel.org>,
	Tom Herbert <tom@...bertland.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Jiri Benc <jbenc@...hat.com>
Subject: Re: [PATCH net-next 3/4] vxlan: remove gro_cell support

On Thu, 2016-07-07 at 17:58 +0200, Paolo Abeni wrote:
> GRO is now handled entirely by the udp_offload layer and  there is no need
> for trying it again at the device level. We can drop gro_cell usage,
> simplifying the driver a bit, while maintaining the same performance for
> TCP and improving slightly for UDP.
> This basically reverts the commit 58ce31cca1ff ("vxlan: GRO support
> at tunnel layer")

Note that gro_cells provide GRO support after RPS, so this helps when we
must perform TCP checksum computation, if NIC lacks CHECKSUM_COMPLETE

(Say we receive packets all steered to a single RX queue due to RSS hash
being computed on outer header only)

Some people disable GRO on the physical device, but enable GRO on the
tunnels.