Re: [RFC PATCH 00/14] Introducing AF_PACKET V4 support

[Alexei Starovoitov <ast@fb.com>]

On 11/14/17 4:20 AM, Willem de Bruijn wrote:
>>>>>
>>>>> * 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.

are you suggesting to use new af_zerocopy for rx and old
af_packet for tx ? imo that's too cumbersome to use.
New interface has to be symmetrical from the start.