netdev - Re: [PATCH v2 5/5] ixgbe: add AF

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Date:   Tue, 2 Oct 2018 11:26:50 -0700
From:   William Tu <u9012063@...il.com>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     jeffrey.t.kirsher@...el.com, intel-wired-lan@...ts.osuosl.org,
        Björn Töpel <bjorn.topel@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Test <tuc@...are.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: Re: [PATCH v2 5/5] ixgbe: add AF_XDP zero-copy Tx support

On Tue, Oct 2, 2018 at 1:01 AM Björn Töpel <bjorn.topel@...il.com> wrote:
>
> From: Björn Töpel <bjorn.topel@...el.com>
>
> This patch adds zero-copy Tx support for AF_XDP sockets. It implements
> the ndo_xsk_async_xmit netdev ndo and performs all the Tx logic from a
> NAPI context. This means pulling egress packets from the Tx ring,
> placing the frames on the NIC HW descriptor ring and completing sent
> frames back to the application via the completion ring.
>
> The regular XDP Tx ring is used for AF_XDP as well. This rationale for
> this is as follows: XDP_REDIRECT guarantees mutual exclusion between
> different NAPI contexts based on CPU id. In other words, a netdev can
> XDP_REDIRECT to another netdev with a different NAPI context, since
> the operation is bound to a specific core and each core has its own
> hardware ring.
>
> As the AF_XDP Tx action is running in the same NAPI context and using
> the same ring, it will also be protected from XDP_REDIRECT actions
> with the exact same mechanism.
>
> As with AF_XDP Rx, all AF_XDP Tx specific functions are added to
> ixgbe_xsk.c.
>
> Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
> ---

Thanks!
Tested-by: William Tu <u9012063@...il.com>