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

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Message-ID: <CAEh+42hN8wL7bbALB8SGCKvum2pzT3R0kXUtMfQPg-XP-QZ7Dg@mail.gmail.com>
Date:	Fri, 8 Jan 2016 16:42:54 -0800
From:	Jesse Gross <jesse@...nel.org>
To:	pravin shelar <pshelar@....org>
Cc:	Paolo Abeni <pabeni@...hat.com>,
	Linux Kernel Network Developers <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 2:53 PM, pravin shelar <pshelar@....org> wrote:
> 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.

How would you influence the allocation for non-internal devices?