From: "Toke Høiland-Jørgensen" <toke@redhat•com>
To: Jamal Hadi Salim <hadi@mojatatu•com>
Cc: Jamal Hadi Salim <jhs@mojatatu•com>,
Jiri Pirko <jiri@resnulli•us>,
John Fastabend <john.fastabend@gmail•com>,
Willem de Bruijn <willemb@google•com>,
Stanislav Fomichev <sdf@google•com>,
Jakub Kicinski <kuba@kernel•org>,
netdev@vger•kernel.org, kernel@mojatatu•com,
deb.chatterjee@intel•com, anjali.singhai@intel•com,
namrata.limaye@intel•com, khalidm@nvidia•com, tom@sipanda•io,
pratyush@sipanda•io, xiyou.wangcong@gmail•com,
davem@davemloft•net, edumazet@google•com, pabeni@redhat•com,
vladbu@nvidia•com, simon.horman@corigine•com,
stefanc@marvell•com, seong.kim@amd•com, mattyk@nvidia•com,
dan.daly@intel•com, john.andy.fingerhut@intel•com
Subject: Re: [PATCH net-next RFC 00/20] Introducing P4TC
Date: Mon, 30 Jan 2023 21:21:32 +0100 [thread overview]
Message-ID: <87wn53wz77.fsf@toke.dk> (raw)
In-Reply-To: <CAAFAkD9Sh5jbp4qkzxuS+J3PGdtN-Kc2HdP8CDqweY36extSdA@mail.gmail.com>
Jamal Hadi Salim <hadi@mojatatu•com> writes:
> On Mon, Jan 30, 2023 at 12:04 PM Toke Høiland-Jørgensen <toke@redhat•com> wrote:
>>
>> Jamal Hadi Salim <jhs@mojatatu•com> writes:
>>
>> > So i dont have to respond to each email individually, I will respond
>> > here in no particular order. First let me provide some context, if
>> > that was already clear please skip it. Hopefully providing the context
>> > will help us to focus otherwise that bikeshed's color and shape will
>> > take forever to settle on.
>> >
>> > __Context__
>> >
>> > I hope we all agree that when you have 2x100G NIC (and i have seen
>> > people asking for 2x800G NICs) no XDP or DPDK is going to save you. To
>> > visualize: one 25G port is 35Mpps unidirectional. So "software stack"
>> > is not the answer. You need to offload.
>>
>> I'm not disputing the need to offload, and I'm personally delighted that
>> P4 is breaking open the vendor black boxes to provide a standardised
>> interface for this.
>>
>> However, while it's true that software can't keep up at the high end,
>> not everything runs at the high end, and today's high end is tomorrow's
>> mid end, in which XDP can very much play a role. So being able to move
>> smoothly between the two, and even implement functions that split
>> processing between them, is an essential feature of a programmable
>> networking path in Linux. Which is why I'm objecting to implementing the
>> P4 bits as something that's hanging off the side of the stack in its own
>> thing and is not integrated with the rest of the stack. You were touting
>> this as a feature ("being self-contained"). I consider it a bug.
>>
>> > Scriptability is not a new idea in TC (see u32 and pedit and others in
>> > TC).
>>
>> u32 is notoriously hard to use. The others are neat, but obviously
>> limited to particular use cases.
>
> Despite my love for u32, I admit its user interface is cryptic. I just
> wanted to point out to existing samples of scriptable and offloadable
> TC objects.
>
>> Do you actually expect anyone to use P4
>> by manually entering TC commands to build a pipeline? I really find that
>> hard to believe...
>
> You dont have to manually hand code anything - its the compilers job.
Right, that was kinda my point: in that case the compiler could just as
well generate a (set of) BPF program(s) instead of this TC script thing.
>> > IOW, we are reusing and plugging into a proven and deployed mechanism
>> > with a built-in policy driven, transparent symbiosis between hardware
>> > offload and software that has matured over time. You can take a
>> > pipeline or a table or actions and split them between hardware and
>> > software transparently, etc.
>>
>> That's a control plane feature though, it's not an argument for adding
>> another interpreter to the kernel.
>
> I am not sure what you mean by control, but what i described is kernel
> built in. Of course i could do more complex things from user space (if
> that is what you mean as control).
"Control plane" as in SDN parlance. I.e., the bits that keep track of
configuration of the flow/pipeline/table configuration.
There's no reason you can't have all that infrastructure and use BPF as
the datapath language. I.e., instead of:
tc p4template create pipeline/aP4proggie numtables 1
... + all the other stuff to populate it
you could just do:
tc p4 create pipeline/aP4proggie obj_file aP4proggie.bpf.o
and still have all the management infrastructure without the new
interpreter and associated complexity in the kernel.
>> > This hammer already meets our goals.
>>
>> That 60k+ line patch submission of yours says otherwise...
>
> This is pretty much covered in the cover letter and a few responses in
> the thread since.
The only argument for why your current approach makes sense I've seen
you make is "I don't want to rewrite it in BPF". Which is not a
technical argument.
I'm not trying to be disingenuous here, BTW: I really don't see the
technical argument for why the P4 data plane has to be implemented as
its own interpreter instead of integrating with what we have already
(i.e., BPF).
-Toke
next prev parent reply other threads:[~2023-01-30 20:22 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-24 17:03 [PATCH net-next RFC 00/20] Introducing P4TC Jamal Hadi Salim
2023-01-26 23:30 ` Jakub Kicinski
2023-01-27 13:33 ` Jamal Hadi Salim
2023-01-27 17:18 ` Jakub Kicinski
2023-01-27 19:42 ` Jamal Hadi Salim
2023-01-28 1:34 ` Singhai, Anjali
2023-01-28 21:17 ` Tom Herbert
2023-01-29 2:09 ` Stephen Hemminger
2023-01-30 3:09 ` Singhai, Anjali
2023-01-30 17:05 ` Tom Herbert
2023-01-27 18:26 ` Jiri Pirko
2023-01-27 20:04 ` Jamal Hadi Salim
2023-01-27 22:26 ` sdf
2023-01-27 23:06 ` Tom Herbert
2023-01-28 0:47 ` Stanislav Fomichev
2023-01-28 1:32 ` Tom Herbert
2023-01-27 23:27 ` Jamal Hadi Salim
2023-01-28 0:47 ` Stanislav Fomichev
2023-01-28 13:37 ` Willem de Bruijn
2023-01-28 15:10 ` Jamal Hadi Salim
2023-01-28 15:33 ` Willem de Bruijn
2023-01-29 5:39 ` John Fastabend
2023-01-29 11:11 ` Jamal Hadi Salim
2023-01-29 11:19 ` Jamal Hadi Salim
2023-01-30 4:30 ` John Fastabend
2023-01-30 10:13 ` Jiri Pirko
2023-01-30 11:26 ` Toke Høiland-Jørgensen
2023-01-30 14:06 ` Jamal Hadi Salim
2023-01-30 14:42 ` Andrew Lunn
2023-01-30 15:31 ` Jamal Hadi Salim
2023-01-30 17:04 ` Toke Høiland-Jørgensen
2023-01-30 19:02 ` Jamal Hadi Salim
2023-01-30 20:21 ` Toke Høiland-Jørgensen [this message]
2023-01-30 21:10 ` John Fastabend
2023-01-30 21:20 ` Toke Høiland-Jørgensen
2023-01-30 22:53 ` Jamal Hadi Salim
2023-01-30 23:24 ` Singhai, Anjali
2023-01-31 0:06 ` John Fastabend
2023-01-31 0:26 ` Jamal Hadi Salim
2023-01-31 4:12 ` Jakub Kicinski
2023-01-31 10:27 ` Jamal Hadi Salim
2023-01-31 10:30 ` Jamal Hadi Salim
2023-01-31 19:10 ` Jakub Kicinski
2023-01-31 22:32 ` Jamal Hadi Salim
2023-01-31 22:36 ` Jakub Kicinski
2023-01-31 22:50 ` Jamal Hadi Salim
2023-01-30 23:32 ` John Fastabend
2023-01-31 12:17 ` Toke Høiland-Jørgensen
2023-01-31 12:37 ` Jiri Pirko
2023-01-31 14:38 ` Jiri Pirko
2023-01-31 17:01 ` Toke Høiland-Jørgensen
2023-01-31 22:23 ` Jamal Hadi Salim
2023-01-31 22:53 ` Toke Høiland-Jørgensen
2023-01-31 23:31 ` Jamal Hadi Salim
2023-02-01 18:08 ` Toke Høiland-Jørgensen
2023-02-02 18:50 ` Jamal Hadi Salim
2023-02-02 23:34 ` Tom Herbert
2023-01-30 22:41 ` Tom Herbert
2023-02-14 17:07 ` Edward Cree
2023-02-14 20:44 ` Jamal Hadi Salim
2023-02-16 20:24 ` Jamal Hadi Salim
2023-01-29 11:02 ` Jamal Hadi Salim
2023-01-29 22:14 ` Toke Høiland-Jørgensen
2023-01-28 13:41 ` Jamal Hadi Salim
2023-01-27 23:02 ` Daniel Borkmann
2023-01-27 23:57 ` Jamal Hadi Salim
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