netdev - Re: [RFC PATCH 00/14] Introducing AF

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Message-ID: <CAF=yD-KWU50xHUrb4RDLCKDD4hJMw=bpCv29GdnHt_h8MAcjrA@mail.gmail.com>
Date:   Tue, 14 Nov 2017 07:20:47 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     Björn Töpel <bjorn.topel@...il.com>,
        Alexei Starovoitov <ast@...com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        "Duyck, Alexander H" <alexander.h.duyck@...el.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        michael.lundkvist@...csson.com, ravineet.singh@...csson.com,
        Daniel Borkmann <daniel@...earbox.net>,
        Netdev <netdev@...r.kernel.org>,
        Tushar Dave <tushar.n.dave@...cle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        "Singhai, Anjali" <anjali.singhai@...el.com>,
        "Rosen, Rami" <rami.rosen@...el.com>,
        "Shaw, Jeffrey B" <jeffrey.b.shaw@...el.com>,
        "Yigit, Ferruh" <ferruh.yigit@...el.com>,
        "Zhang, Qi Z" <qi.z.zhang@...el.com>,
        David Miller <davem@...emloft.net>
Subject: Re: [RFC PATCH 00/14] Introducing AF_PACKET V4 support

>>>>
>>>> * Limit the scope of the first patchset to Rx only, and introduce Tx
>>>>   in a separate patchset.
>>>
>>>
>>> all sounds good to me except above bit.
>>> I don't remember people suggesting to split it this way.
>>> What's the value of it without tx?
>>>
>>
>> We definitely need Tx for our use-cases! I'll rephrase, so the
>> idea was making the initial patch set without Tx *driver*
>> specific code, e.g. use ndo_xdp_xmit/flush at a later point.
>>
>> So AF_ZEROCOPY, the socket parts, would have Tx support.
>>
>> @John Did I recall that correctly?
>>
>
> Yep, that is what I said. However, on second thought, without the
> driver tx half I guess tx will be significantly slower.

The idea was that existing packet rings already send without
copying, so the benefit from device driver changes is not obvious.

I would leave them out for now and evaluate before possibly
sending a separate patchset.