Re: [dpdk-dev] [PATCH] ixgbe: fix icc issue with mbuf initializer

[Bruce Richardson <bruce.richardson@intel.com>]

On Mon, Nov 03, 2014 at 01:31:10PM +0100, David Marchand wrote:
> Hello Bruce,
> 
> On Mon, Nov 3, 2014 at 12:11 PM, Bruce Richardson <
> bruce.richardson@intel.com> wrote:
> 
> > diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
> > b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
> > index e813e43..b57c588 100644
> > --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
> > +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
> > @@ -730,16 +730,15 @@ static struct ixgbe_txq_ops vec_txq_ops = {
> >  int
> >  ixgbe_rxq_vec_setup(struct igb_rx_queue *rxq)
> >  {
> > -       struct rte_mbuf mb_def = {
> > -               .nb_segs = 1,
> > -               .data_off = RTE_PKTMBUF_HEADROOM,
> > -#ifdef RTE_MBUF_REFCNT
> > -               { .refcnt = 1, }
> > -#endif
> > -       };
> > +       struct rte_mbuf mb_def = { .buf_addr = 0 }; /* zeroed mbuf */
> >
> > +       mb_def.nb_segs = 1;
> > +       mb_def.data_off = RTE_PKTMBUF_HEADROOM;
> >         mb_def.buf_len = rxq->mb_pool->elt_size - sizeof(struct rte_mbuf);
> >         mb_def.port = rxq->port_id;
> > +#ifdef RTE_MBUF_REFCNT
> > +       mb_def.refcnt = 1;
> > +#endif
> >         rxq->mbuf_initializer = *((uint64_t *)&mb_def.rearm_data);
> >         return 0;
> >  }
> >
> 
> I would expect we use rte_mbuf_refcnt_set / rte_mbuf_refcnt_read to access
> this "refcnt" field.
> This api handles both RTE_MBUF_REFCNT_ATOMIC and ! RTE_MBUF_REFCNT_ATOMIC
> configs.
> But I suppose this is fine at init time (since the union will initialize
> properly the field).

It's a good point, I'll update patch to use the appropriate macro which will clean up the code a bit.

/Bruce

> 
> By the way, why do we have this RTE_MBUF_REFCNT_ATOMIC option ?
> From my point of view, there is not much use of a refcnt that is not atomic
> :-).
> 
> 
> -- 
> David Marchand