Re: [dpdk-dev] [RFC 0/3] ethdev: add ptype as Rx offload

[Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>]

>-----Original Message-----
>From: Hemant Agrawal <hemant.agrawal@nxp.com>
>Sent: Tuesday, August 6, 2019 1:49 PM
>To: Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>; Jerin
>Jacob Kollanukkaran <jerinj@marvell.com>
>Cc: dev@dpdk.org
>Subject: RE: [dpdk-dev] [RFC 0/3] ethdev: add ptype as Rx offload
>>
>> Add PTYPE to DEV_RX_OFFLOAD_* flags.
>>
>> Currently, most of the NICs already support PTYPE parsing and update
>the
>> mbuf->packet_type through an internal lookup table, but there is no
>way to
>> disable the lookup if the application is not intrested in ptypes
>returned by
>> `rte_eth_dev_get_supported_ptypes`.
>>
>[Hemant]  it will also mean introducing another check in datapath, if the
>application has asked for PTYPE offload - copy the results to mbuf-
>>packet_type otherwise don't do it.
>

I think that having the check would give better performance than loading ptype table to L1 
doing  a lookup and copying it to mbuf when the application doesn't need it.

>Your second patch is incomplete in the sense that it only adds the
>capability. But it does not disable the lookups?

It is upto the maintainer of the PMD to disable the lookup in data path. If there is a scope of optimization 
then they could do it. There is no harm in exposing  PTYPE even RX_OFFLOAD_PTYPE is not enabled.
I was hesitant to touch data path as it would be impossible to verify performance effect on all NICs.