netdev - Re: [RFC net-next 0/2] net/sched: cls_flower, act

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Message-ID: <20160815113653.GD19058@office.localdomain>
Date:	Mon, 15 Aug 2016 14:36:53 +0300
From:	Amir Vadai <amir@...ai.me>
To:	Jamal Hadi Salim <jhs@...atatu.com>
Cc:	Shmulik Ladkani <shmulik.ladkani@...il.com>,
	Jiri Pirko <jiri@...nulli.us>,
	Cong Wang <xiyou.wangcong@...il.com>,
	John Fastabend <john.fastabend@...il.com>,
	Jiri Pirko <jiri@...lanox.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Hadar Har-Zion <hadarh@...lanox.com>,
	Oded Shanoon <odeds@...lanox.com>,
	Amir Vadai <amirva@...lanox.com>
Subject: Re: [RFC net-next 0/2] net/sched: cls_flower, act_mirred: VXLAN
 redirect using TC

On Mon, Aug 15, 2016 at 06:41:14AM -0400, Jamal Hadi Salim wrote:
> On 16-08-15 06:24 AM, Shmulik Ladkani wrote:
> > On Mon, 15 Aug 2016 06:08:10 -0400, jhs@...atatu.com wrote:
> 
> > > Assuming $VXLAN is actually not a linux netdev of type vxlan?
> > > then the action does vxlan encap redirect sends it to the $VXLAN
> > > dev with encapsulation in place.
> > 
> > I assume Amir refers to vxlan netdev in VXLAN_F_COLLECT_METADATA mode,
> > using the tun_info metadata found in skb_metadata_dst.
> > The action is supposed to assign the tun metadata.
> > 
> 
> I see - so you let the vxlan netdev do the encap?
> Would it still scale to a _very large_ number of tunnels?
> How many netdevs are you going to use? I am assuming you will hit
> a nasty lock somewhere(qdisc?) if you use only one.
Having a netdev per tunnel is problematic in its memory use [1].
User can take each of the approaches. Can have a shared netdev, but will
have some contention on the qdisc lock, or create a vxlan dev per VNI
and increase memory use.
When offloading will be added, shared netdev will enjoy all worlds - low
memory use and no lock contention.


[1] - http://www.netdevconf.org/1.1/proceedings/slides/ahern-aleksandrov-prabhu-scaling-network-cumulus.pdf

> 
> cheers,
> jamal