Re: [PATCH v3] net/af_xdp: re-enable secondary process support

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 2/8/2022 6:42 PM, Stephen Hemminger wrote:
> On Tue, 8 Feb 2022 18:00:27 +0000
> Ferruh Yigit <ferruh.yigit@intel.com> wrote:
> 
>> On 2/8/2022 5:45 PM, Stephen Hemminger wrote:
>>> On Tue,  8 Feb 2022 13:48:00 +0000
>>> Ciara Loftus <ciara.loftus@intel.com> wrote:
>>>    
>>>> +- **Secondary Processes**
>>>> +
>>>> +  Rx and Tx are not supported for secondary processes due to the single-producer
>>>> +  single-consumer nature of the AF_XDP rings. However other operations including
>>>> +  statistics retrieval are permitted.
>>>> +  The maximum number of queues permitted for PMDs operating in this model is 8
>>>> +  as this is the maximum number of fds that can be sent through the IPC APIs as
>>>> +  defined by RTE_MP_MAX_FD_NUM.
>>>> +
>>>
>>> This seems like a restriction that is true for most devices in DPDK.
>>> Most other devices also have restriction that on queues;
>>> the hardware descriptor ring can only be used by one thread at a time.
>>> Is this different with AF_XDP?
>>
>> I asked the same on v2 :) and Ciara explained the reason, it is on v2 discussion thread.
> 
> The wording of the message is what confused me.
> It would be better to change:
>      due to the single-producer single-consumer nature of the AF_XDP rings
> to
>      due to memory mapping of the AF_XDP rings being assigned by the kernel
>      in the primary process only.

+1