[Codel] Re: [Bloat] Re: [Cake] Re: XDP2 is here - from one and only Tom Herbert (almost to the date, 10 years after XDP was released)

[Tom Herbert <tom@herbertland.com>]

On Wed, Sep 10, 2025, 1:54 AM <BeckW@telekom.de> wrote:

> Interesting work! One problem of P4 is that the networking hardware varies
> so much in number of resources (queues, schedulers, policers, counters,
> table memory) that the code inevitably becomes tied to a certain system.
> It will be difficult to abstract the peculiarities of systems -- eg
> Broadcom 88800 vs linux kernel -- in a good way.
>

Hi Wolfgang

>
Yes, the non-portability of P4 code between different architectures has
been raised as an issue. I believe this is subset of the general problem
that we need to deal with differing resource constraints across targets
(like different memory resources, hardware accelerators, table sizes, etc
). It should be a problem of resource constraints, and not differences in
core functionality supported by the targets

I think there's three possibilities:

1) We create an image and attempt to resolve the resource constraints at
runtime (load time). Determine the resources and run with those. It's
possible that a HW configuration doesn't have sufficient resources to meet
the programmer's requirements in which case we may have to inform the user
the program can't run (e.g.if the programmer wants line rate encryption,
but there's no HW accelerators then the program requirements can't be met
and the program can't run on that target).
2) Recompile the backend to the different targets. This is needed when the
executable is incompatible between targets. The goal is to still be
transparent to the user, but we still need to meet the requirement of the
application.
3) Change the source code if the hardware peculiarities are not transparent
to program source. Obviously, this is the least preferred option, but if
there's no alternative then the goal here would be to isolate the target
specific code as much as possible. Hopefully, the vast majority of program
code is target agnostic and there's just a little glue code for each target.

Tom



> Wolfgang
>
> -----Ursprüngliche Nachricht-----
> Von: Tom Herbert via Bloat <bloat@lists.bufferbloat.net>
> Gesendet: Dienstag, 9. September 2025 23:37
> An: Frantisek Borsik <frantisek.borsik@gmail.com>
> Cc: David P. Reed <dpreed@deepplum.com>; Cake List <
> cake@lists.bufferbloat.net>; codel@lists.bufferbloat.net; bloat <
> bloat@lists.bufferbloat.net>; Jeremy Austin via Rpm <
> rpm@lists.bufferbloat.net>
> Betreff: [Bloat] Re: [Cake] Re: XDP2 is here - from one and only Tom
> Herbert (almost to the date, 10 years after XDP was released)
>
> On Tue, Sep 9, 2025, 5:03 PM Frantisek Borsik <frantisek.borsik@gmail.com>
> wrote:
>
> > Thanks a lot, David.
> >
> > I have asked Tom if he wants to join us and he should be here to chat
> > with us now.
> >
> > All the best,
> >
> > Frank
> >
> > Frantisek (Frank) Borsik
> >
> >
> > *In loving memory of Dave Täht: *1965-2025
> >
> > https://deu01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flibr
> > eqos.io%2F2025%2F04%2F01%2Fin-loving-memory-of-dave%2F&data=05%7C02%7C
> > BeckW%40telekom.de%7C299d64b9b76b4d4cf88b08ddf039e105%7Cbde4dffc4b604c
> > f68b04a5eeb25f5c4f%7C0%7C0%7C638930853609276702%7CUnknown%7CTWFpbGZsb3
> > d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoi
> > TWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=TAA6NdEkB3KQQt8UhKqs3ZKuLj
> > N7A9h9J9FAjNRDDuU%3D&reserved=0
> >
> >
> > https://deu01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.
> > linkedin.com%2Fin%2Ffrantisekborsik&data=05%7C02%7CBeckW%40telekom.de%
> > 7C299d64b9b76b4d4cf88b08ddf039e105%7Cbde4dffc4b604cf68b04a5eeb25f5c4f%
> > 7C0%7C0%7C638930853609297031%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiO
> > nRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%
> > 3D%3D%7C0%7C%7C%7C&sdata=ucL7U%2FQ81ks09nVEGUbe%2FFq1rhJNLaegicv%2FLCV
> > cIlg%3D&reserved=0
> >
> > Signal, Telegram, WhatsApp: +421919416714
> >
> > iMessage, mobile: +420775230885
> >
> > Skype: casioa5302ca
> >
> > frantisek.borsik@gmail.com
> >
> >
> > On Tue, Sep 9, 2025 at 10:25 PM David P. Reed <dpreed@deepplum.com>
> wrote:
> >
> > > Hi Frank -
> > >
> > >
> > >
> > > I think it is interesting as a concept. A project I am advising has
> > > been using DPDK very effectively to get rid of the huge path and
> > > locking
> > delays
> > > in the current Linux network stack. XDP2 could be supported in a
> > > ring3
> > > (user) address space, achieving a similar result.
> >
>
> HI David,
>
> The idea is you could write the code in XDP2 and it would be compiled to
> DPDK or eBPF and the compiler would handle the optimizations.
>
>
> > >
> > >
> > >
> > > But I don't think XDP2 is going that direction - so it may be
> > > stuckinto the mess of kernel space networking. Adding eBPF only has
> > > made this more
> > of
> > > a mess, by the way (and adding a new "compiler" that needs to be
> > > veriried as safe for the kernel).
>
>
> Think of XDP2 as the generalization of XDP to go beyond just the kernel.
> The idea is that the user writes their datapath code once and they compile
> it to run in whatever targets they have-- DPDK, P4, other programmable
> hardware, and yes XDP/eBPF. It's really not limited to kernel networking.
>
> As for the name XDP2, when we created XDP, eXpress DataPath, my vision was
> that it would be implementation agnostic. eBPF was the first instantiation
> for practicality, but now ten years later I think we can realize the
> initial vision.
>
> Tom
>
>
>
> >
> > > I will be watching how this evolves.
> > >
> > >
> > >
> > > David
> > >
> > >
> > >
> > > On Tuesday, September 9, 2025 06:32, "Frantisek Borsik" <
> > > frantisek.borsik@gmail.com> said:
> > >
> > > > Hello to all,
> > > >
> > > > Looks interesting:
> > > >
> > >
> > https://deu01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmedi
> > um.com%2F%40tom_84912%2Fxdp2-this-changes-everything-at-least-for-ai-m
> > l-infrastructure-850c1ba82771&data=05%7C02%7CBeckW%40telekom.de%7C299d
> > 64b9b76b4d4cf88b08ddf039e105%7Cbde4dffc4b604cf68b04a5eeb25f5c4f%7C0%7C
> > 0%7C638930853609308950%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWU
> > sIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%
> > 7C0%7C%7C%7C&sdata=RTLHTVFR540C8Psr73uiuRvkx1sSyjmlUIICEHFj0HA%3D&rese
> > rved=0
> > > >
> > > >
> > > > All the best,
> > > >
> > > > Frank
> > > >
> > > > Frantisek (Frank) Borsik
> > > >
> > > >
> > > > *In loving memory of Dave Täht: *1965-2025
> > > >
> > > > https://deu01.safelinks.protection.outlook.com/?url=https%3A%2F%2F
> > > > libreqos.io%2F2025%2F04%2F01%2Fin-loving-memory-of-dave%2F&data=05
> > > > %7C02%7CBeckW%40telekom.de%7C299d64b9b76b4d4cf88b08ddf039e105%7Cbd
> > > > e4dffc4b604cf68b04a5eeb25f5c4f%7C0%7C0%7C638930853609323027%7CUnkn
> > > > own%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAi
> > > > OiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=98
> > > > musUCMTZR4ID%2Bo6GYxWOX99aiYBspBUdh%2BNV1fzwc%3D&reserved=0
> > > >
> > > >
> > > > https://deu01.safelinks.protection.outlook.com/?url=https%3A%2F%2F
> > > > www.linkedin.com%2Fin%2Ffrantisekborsik&data=05%7C02%7CBeckW%40tel
> > > > ekom.de%7C299d64b9b76b4d4cf88b08ddf039e105%7Cbde4dffc4b604cf68b04a
> > > > 5eeb25f5c4f%7C0%7C0%7C638930853609334239%7CUnknown%7CTWFpbGZsb3d8e
> > > > yJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjo
> > > > iTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=0rD47zFeLVV1YDqMc5SO0
> > > > xGWEOTrE3FOYv0mOqGF%2FW4%3D&reserved=0
> > > >
> > > > Signal, Telegram, WhatsApp: +421919416714
> > > >
> > > > iMessage, mobile: +420775230885
> > > >
> > > > Skype: casioa5302ca
> > > >
> > > > frantisek.borsik@gmail.com
> > > > _______________________________________________
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