[dpdk-dev] [PATCH v2 04/15] node: switch IPv4 metadata to dynamic mbuf field

[Thomas Monjalon]

27/10/2020 15:23, Nithin Dabilpuram:
> On Mon, Oct 26, 2020 at 11:20:02PM +0100, Thomas Monjalon wrote:
> > The node_mbuf_priv1 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>
> > ---
> > --- a/lib/librte_node/ip4_lookup.c
> > +++ b/lib/librte_node/ip4_lookup.c
> > +int node_mbuf_priv1_dynfield_offset;
> > +
> 
> This change doesn't work in secondary as it is process local memory.

Yes that's an issue.
Can we copy the value when starting a secondary process?

[...]
> >  static __rte_always_inline struct node_mbuf_priv1 *
> >  node_mbuf_priv1(struct rte_mbuf *m)
> >  {
> > -	return (struct node_mbuf_priv1 *)&m->udata64;
> > +	return RTE_MBUF_DYNFIELD(m,
> > +		node_mbuf_priv1_dynfield_offset, struct node_mbuf_priv1 *);
> 
> There is a performance regression of ~1.4% in our platform (Octeontx2) because
> of this	change.

Yes that's the price to pay for a more extensible DPDK.
It is much cheaper than not having room for new features,
or having features conflicting on the same mbuf field like here.