On 7/1/2022 1:24 PM, Shijith Thotton wrote:
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 <sthot...@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.
'RTE_PCI_DRV_NEED_IOVA_AS_VA' means device can *only* work in
RTE_IOVA_VA mode, right?
Although there are many devices that support RTE_IOVA_VA mode, only a
few of them works *only* with RTE_IOVA_VA mode, rest can prefer to use
RTE_IOVA_PA or RTE_IOVA_VA.
Also using KNI forces to use RTE_IOVA_PA mode.
And moving 'buf_iova' filed out of first cache will impact the
performance for RTE_IOVA_PA mode.
Since KNI is going away and vfio is more preferred way, it can be OK to
make 'buf_iova' dynamic filed in long term, but I think it is better to
do this slowly, like should we wait for KNI to go away first?
How much of a performance gain?
No change in performance.
