netdev - Re: [RFC PATCH 00/17] xdp: Add packet queueing and scheduling capabilities

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Message-ID: <CAM0EoMmHi=R2bwGQC9aUh+xjpCHWGu3oXhE_1BVvcZbOfx7bSA@mail.gmail.com>
Date:   Thu, 14 Jul 2022 11:33:55 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Dave Taht <dave.taht@...il.com>
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Mykola Lysenko <mykolal@...com>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>,
        Freysteinn Alfredsson <freysteinn.alfredsson@....se>,
        Cong Wang <xiyou.wangcong@...il.com>
Subject: Re: [RFC PATCH 00/17] xdp: Add packet queueing and scheduling capabilities

On Thu, Jul 14, 2022 at 10:56 AM Dave Taht <dave.taht@...il.com> wrote:
>
> In general I feel a programmable packet pacing approach is the right
> way forward for the internet as a whole.
>
> It lends itself more easily and accurately to offloading in an age
> where it is difficult to do anything sane within a ms on the host
> cpu, especially in virtualized environments, in the enormous dynamic
> range of kbits/ms to gbits/ms between host an potential recipient [1]
>
> So considerations about what is easier to offload moving forward vs
> central cpu costs should be in this conversation.
>

If you know your hardware can offload - there is a lot less to worry about.
You can let the synchronization be handled by hardware. For example,
if your hardware can do strict priority scheduling/queueing you really
should bypass the kernel layer, set appropriate metadata (skb prio)
and let the hw handle it. See the HTB offload from Nvidia.
OTOH, EDT based approaches are the best for some lightweight
approach which takes advantage of simple hardware
features (like timestamps, etc).

cheers,
jamal