Re: [PATCH] net/ring: Set mbuf->port for received packets

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

On 6/18/2024 8:14 PM, Sriram Yagnaraman wrote:
> Hi Morten,
> 
>> -----Original Message-----
>> From: Morten Brørup <mb@smartsharesystems.com>
>> Sent: Tuesday, 18 June 2024 18:01
>> To: Sriram Yagnaraman <sriram.yagnaraman@ericsson.com>
>> Cc: dev@dpdk.org; Bruce Richardson <bruce.richardson@intel.com>
>> Subject: RE: [PATCH] net/ring: Set mbuf->port for received packets
>>
>> [Du får inte e-post ofta från mb@smartsharesystems.com. Läs om varför det
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>>
>>> From: Sriram Yagnaraman [mailto:sriram.yagnaraman@ericsson.com]
>>>
>>> When using ring based ethdev, mbuf->port is not set on received packets.
>>>
>>> For applications that use the mbuf->port to identify the incoming
>>> port, especially when eventdev RX adapter pulls the packet on a
>>> different core and the application running on a worker core has no
>>> clue on the incoming port. This change adds some cycles at receive, to
>>> set the port of course.
>>
>> I agree that the mbuf->port field must be set before returning from
>> rte_eth_rx_burst().
>>
>> I'm not aware how applications use the ring based ethdev, so I might be
>> asking silly questions...
>>
>> How about all the other mbuf fields normally set by the PMD before
>> returning from rte_eth_rx_burst()?
>>
>> Is the enqueueing core supposed to set them?
> 
> I am integrating a couple of existing DPDK applications, and they use rte_eth_* API between them today. To keep the API consistent, and not make too many changes in the applications themselves, net_ring seems to be the best option. If someone has a better idea, I would love to hear.
> 

I think it is a practical usage of ring PMD, and I am OK for the update.
There is a question in the commit log, I will remove it while merging.

> There are no "HW" offloads when using net_ring, and IIUC there are no HW related fields that can be set at rx_burst.
> So, apart from port field, I didn't see much else that needed to be set.
> 
>>
>> Or if the ring is only used for queueing packets originally received (at a
>> physical port) by the enqueueing core, why not keep the mbuf->port value
>> from the original reception?
> 
> In my case the enqueuing application originates the flow from SW, so the rte_mbuf does not come from a NIC.
> 
>>
>>>
>>> Please advise if this change is something that can be upstreamed.
>>>
>>> Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@ericsson.com>
>