netdev - Re: [PATCH 11/11] doc/af_xdp: include unaligned chunk case

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Message-ID: <CAJ+HfNiSs1jGzqg0E4f8=8EMCTMpAWs6-33m7o9Gw_8L-5v-TQ@mail.gmail.com>
Date:   Mon, 24 Jun 2019 17:34:15 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Kevin Laatz <kevin.laatz@...el.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        bpf <bpf@...r.kernel.org>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
        Bruce Richardson <bruce.richardson@...el.com>,
        ciara.loftus@...el.com
Subject: Re: [PATCH 11/11] doc/af_xdp: include unaligned chunk case

On Thu, 20 Jun 2019 at 19:25, Kevin Laatz <kevin.laatz@...el.com> wrote:
>
> The addition of unaligned chunks mode, the documentation needs to be
> updated to indicate that the incoming addr to the fill ring will only be
> masked if the user application is run in the aligned chunk mode. This patch
> also adds a line to explicitly indicate that the incoming addr will not be
> masked if running the user application in the unaligned chunk mode.
>
> Signed-off-by: Kevin Laatz <kevin.laatz@...el.com>

Acked-by: Björn Töpel <bjorn.topel@...el.com>

> ---
>  Documentation/networking/af_xdp.rst | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/networking/af_xdp.rst b/Documentation/networking/af_xdp.rst
> index e14d7d40fc75..16fbc68cac50 100644
> --- a/Documentation/networking/af_xdp.rst
> +++ b/Documentation/networking/af_xdp.rst
> @@ -153,10 +153,12 @@ an example, if the UMEM is 64k and each chunk is 4k, then the UMEM has
>
>  Frames passed to the kernel are used for the ingress path (RX rings).
>
> -The user application produces UMEM addrs to this ring. Note that the
> -kernel will mask the incoming addr. E.g. for a chunk size of 2k, the
> -log2(2048) LSB of the addr will be masked off, meaning that 2048, 2050
> -and 3000 refers to the same chunk.
> +The user application produces UMEM addrs to this ring. Note that, if
> +running the application with aligned chunk mode, the kernel will mask
> +the incoming addr.  E.g. for a chunk size of 2k, the log2(2048) LSB of
> +the addr will be masked off, meaning that 2048, 2050 and 3000 refers
> +to the same chunk. If the user application is run in the unaligned
> +chunks mode, then the incoming addr will be left untouched.
>
>
>  UMEM Completion Ring
> --
> 2.17.1
>