[PATCH] mbuf: add mbuf physical address field to dynamic field

[Shijith Thotton]

>> If all devices are configured to run in IOVA mode as VA, physical
>> address field of mbuf (buf_iova) won't be used. In such cases, buf_iova
>> space is free to use as a dynamic field. So a new dynamic field member
>> (dynfield2) is added in mbuf structure to make use of that space.
>>
>> A new mbuf flag RTE_MBUF_F_DYNFIELD2 is introduced to help identify the
>> mbuf that can use dynfield2.
>>
>> Signed-off-by: Shijith Thotton <sthotton at marvell.com>
>
> This seems like a complex and potentially error prone way to do this.
> What is the use case?
>

PCI drivers with the flag RTE_PCI_DRV_NEED_IOVA_AS_VA only works in IOVA mode as
VA. buf_iova field of mbuf is not used by those PMDs and can be used as a
dynamic area to save space.

> How much of a performance gain?

No change in performance.