On Wed, Jul 10, 2019 at 10:49:17AM -0700, Stephen Hemminger wrote:
> On Wed, 10 Jul 2019 11:29:07 +0200
> Olivier Matz <olivier.m...@6wind.com> wrote:
>
> > /**
> > * Indicate that the metadata field in the mbuf is in use.
> > @@ -738,6 +741,8 @@ struct rte_mbuf {
> > */
> > struct rte_mbuf_ext_shared_info *shinfo;
> >
> > + uint64_t dynfield1; /**< Reserved for dynamic fields. */
> > + uint64_t dynfield2; /**< Reserved for dynamic fields. */
> > } __rte_cache_aligned;
>
> Growing mbuf is a fundamental ABI break and this needs
> higher level approval.
The size of the mbuf is still 128, I used the last 16 bytes that
were unused.
Later, we can think about removing existing fields and replace
them by a dynfield area, which can be anywhere in the structure
(even if it is in a 1 byte hole).
> Why not one pointer?
A pointer to what?
> It looks like you are creating something like FreeBSD m_tag.
> Why not use that?
My implementation targets performance (accessing to *(mbuf + offset)
should be nearly as fast as accessing to a static field), at the price
of less flexibility compared to something like FreeBSD m_tag.
