Message-ID: <CA+mtBx9ZVQ5r5Hzy9-uEnk+iu+HKkOP4+VANC06Xf8VvTxktwQ@mail.gmail.com>
Date:	Mon, 22 Sep 2014 15:40:29 -0700
From:	Tom Herbert <therbert@...gle.com>
To:	Thomas Graf <tgraf@...g.ch>
Cc:	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Jiri Pirko <jiri@...nulli.us>,
	John Fastabend <john.r.fastabend@...el.com>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Neil Horman <nhorman@...driver.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	Daniel Borkmann <dborkman@...hat.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Jesse Gross <jesse@...ira.com>,
	Pravin Shelar <pshelar@...ira.com>,
	Andy Zhou <azhou@...ira.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Vladislav Yasevich <vyasevic@...hat.com>,
	Cong Wang <xiyou.wangcong@...il.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Scott Feldman <sfeldma@...ulusnetworks.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Roopa Prabhu <roopa@...ulusnetworks.com>,
	John Linville <linville@...driver.com>,
	"dev@...nvswitch.org" <dev@...nvswitch.org>,
	Jason Wang <jasowang@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	ryazanov.s.a@...il.com, Lennert Buytenhek <buytenh@...tstofly.org>,
	aviadr@...lanox.com, Felix Fietkau <nbd@...nwrt.org>,
	Neil Jerram <Neil.Jerram@...aswitch.com>, ronye@...lanox.com,
	simon.horman@...ronome.com,
	Alexander Duyck <alexander.h.duyck@...el.com>
Subject: Re: [patch net-next v2 8/9] switchdev: introduce Netlink API

On Mon, Sep 22, 2014 at 3:17 PM, Thomas Graf <tgraf@...g.ch> wrote:
> On 09/22/14 at 08:10am, Tom Herbert wrote:
>> Thomas, can you (or someone else) quantify what the host case is. I
>> suppose there may be merit in using a switch on NIC for kernel bypass
>> scenarios, but I'm still having a hard time understanding how this
>> could be integrated into the host stack with benefits that outweigh
>
> Personally my primary interest is on lxc and vm based workloads w/
> end to end encryption, encap, distributed L3 and NAT, and policy
> enforcement including service graphs which imply both east-west
> and north-south traffic patterns on a host. The usual I guess ;-)
>
>> complexity. The history of stateful offloads in NICs is not great, and
>> encapsulation (stuffing a few bytes of header into a packet) is in
>> itself not nearly an expensive enough operation to warrant offloading
>
> No argument here. The direct benchmark comparisons I've measured showed
> only around 2% improvement.
>
> What makes stateful offload interesting to me is that the final
> desintation of a packet is known at RX and can be redirected to a
> queue or VF. This allows to build packet batches on shared pages
> while preserving the securiy model.
>
How is this different from what rx-filtering already does?

> Will the gains outweigh complexity? I hope so but I don't know for
> sure. If you have insights, let me know. What I know for sure is that
> I don't want to rely on a kernel bypass for the above.
>
>> to the NIC. Personally, I wish if NIC vendors are going to focus on
>> stateful offload I rather see it be for encryption which I believe
>> currently does warrant offload at 40G and higher speeds.
>
> Agreed. I would like to be see a focus on both.
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