Re: [RFC 0/8] mbuf: structure reorganization

Hi Olivier,

quoted

quoted

- m->next, m->nb_segs, and m->refcnt are always initialized for
mbufs in the pool, avoiding the need of setting m->next (located in
the 2nd cache line) in the Rx path for mono-segment packets.
- change port and nb_segs to 16 bits

Not that I am completely against it,
but changing nb_segs to 16 bits seems like an overkill to me.
I think we can keep and extra 8bits for something more useful in
future.

In my case, I use the m->next field to chain more than 256 segments for
L4 socket buffers. It also updates nb_seg that can overflow. It's not
a big issue since at the end, nb_seg is decremented for each segment.
On the other hand, if I enable some sanity checks on mbufs, it
complains because the number of segments is not equal to nb_seg.

I still have a hard time imaging some practical use-case for packet
that spawns over 256 segments.
But might that is just my poor imagination, so ok  if you guys believe
there are some real-world use cases - I wouldn't object here.
Konstantin