[dpdk-dev] [RFC] ethdev: introduce Rx buffer split

[Andrew Rybchenko]

On 10/12/20 6:14 PM, Thomas Monjalon wrote:
> 12/10/2020 11:56, Slava Ovsiienko:
>> Hi, Andrew
>>
>> Thank you for the comments.
>>
>> We have two approaches how to specify multiple segments to split Rx packets:
>> 1. update queue configuration structure
>> 2. introduce new rx_queue_setup_ex() routine with extra parameters.
>>
>> For [1] my only actual dislike is that we would have multiple places to specify
>> the pool - in rx_queue_setup() and in the config structure. So, we should
>> implement some checking (if we have offload flag set we should check
>> whether mp parameter is NULL and segment descriptions array pointer/size
>> is provided, if no offload flag set - we must check the description array is empty). 
>>
>>> @Thomas, @Ferruh: I'd like to hear what other ethdev maintainers think
>>> about it.
>>
>> Yes, it would be very nice to hear extra opinions. Do we think the providing
>> of extra API function is worse than extending existing structure, introducing
>> some conditional ambiguity and complicating the parameter compliance
>> check?
> 
> Let's try listing pros and cons of each approach, so we can conclude.
> 
> 1/ update queue config struct
> 
> 	1.1 pro: keep same queue setup function

pro: no code duplication

> 	1.2 con: two mempool pointers (struct or function)
> 	1.3 con: variable size of segment description array
> 
> 2/ new queue setup function
> 
> 	2.1 con: two functions for queue setup

con: code duplication or refactoring of existing stable code

> 	2.2 pro: mempool pointer is not redundant
> 	2.3 pro: segment description array size defined by the caller
> 
> What else I'm missing?
>