netdev - Re: [PATCH net] openvswitch: compute needed headroom for internal vports

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Date:	Fri, 8 Jan 2016 14:53:42 -0800
From:	pravin shelar <pshelar@....org>
To:	Paolo Abeni <pabeni@...hat.com>
Cc:	netdev@...r.kernel.org, Pravin Shelar <pshelar@...ira.com>,
	"David S. Miller" <davem@...emloft.net>,
	Flavio Leitner <fbl@...close.org>
Subject: Re: [PATCH net] openvswitch: compute needed headroom for internal vports

On Fri, Jan 8, 2016 at 1:50 PM, Paolo Abeni <pabeni@...hat.com> wrote:
> Currently the ovs internal vports always use a default needed_headroom.
> This leads to a skb head copy while xmitting on ovs swith via vport
> that add some kind of encapsulation (gre, geneve, etc.).
>
> This patch add book-keeping for the maximum needed_headroom used by
> the non internal vports in any dp, updating it on vport creation and
> deletion.
>
> Said value is than used as needed_headroom for internal vports,
> avoiding the above copy.
>
Why is this done only for internal devices? In most common case of
traffic the packet enters OVS from tap or other netdev type vport
device.

> With ~1000 bytes long frames, this give about a 6% xmit performance
> improvement in case of vxlan tunnels and about 8% when using geneve
> tunnels.
>
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> Acked-by: Flavio Leitner <fbl@...close.org>
> --