[dpdk-dev] [PATCH v2 09/15] net/vmxnet3: switch MSS hint to dynamic mbuf field

[Thomas Monjalon]

27/10/2020 11:45, Olivier Matz:
> On Mon, Oct 26, 2020 at 11:20:07PM +0100, Thomas Monjalon wrote:
> > The segment count, used for MSS guess,
> > was stored in the deprecated mbuf field udata64.
> > It is moved to a dynamic field in order to allow removal of udata64.
> > 
> > Signed-off-by: Thomas Monjalon <thomas at monjalon.net>
> 
> After seeing this commit, I wonder if we shouldn't introduce an
> enhancement in the dynamic field API.
> 
> Previously, the driver used udata64 only internally, so without any
> risk. The risky usages of udata64 were when the mbuf goes out of a
> module.
> 
> Changing to dynamic field makes the code safe for any use, but consumes
> more memory.
> 
> I wonder if we shouldn't (later) introduce a flag RTE_MBUF_DYN_F_SHARED,
> or something similar, to say that this field is only used inside a
> module, and that its memory can be shared with other dynamic fields.

Yes can be a later improvement if the sharing limitations
are properly defined.
We can also share some offsets which are used differently in Rx and Tx.