Hi Ferruh,
On Fri, 9 Jun 2017 12:24:56 +0100, Ferruh Yigit <ferruh.yi...@intel.com> wrote:
> On 6/8/2017 12:22 PM, Shijith Thotton wrote:
> > Avoid re-initializing of mbuf fields which are set while in pool.
> > Replaced lio_recv_buffer_alloc with rte_pktmbuf_alloc.
> >
> > See commit 8f094a9ac5d7 ("mbuf: set mbuf fields while in pool").
> >
> > Signed-off-by: Shijith Thotton <shijith.thot...@caviumnetworks.com>
>
> <...>
>
> > @@ -489,9 +466,6 @@
> > droq->refill_count++;
> >
> > if (likely(nicbuf != NULL)) {
> > - nicbuf->data_off = RTE_PKTMBUF_HEADROOM;
>
> Hi Shijith, Olivier,
>
> nb_segs and next are initialized properly when mbuf allocated, but is
> "data_off = RTE_PKTMBUF_HEADROOM" guaranteed?
>
> > - nicbuf->nb_segs = 1;
> > - nicbuf->next = NULL;
> > /* We don't have a way to pass flags yet */
> > nicbuf->ol_flags = 0;
> > if (rh->r_dh.has_hash) {
>
> <...>
It's not guaranteed when using a raw allocation, i.e. rte_mbuf_raw_alloc()
or rte_mempool_get(). The PMD usually use these functions in Rx path to
fully initialize the mbuf fields on their own.
In this driver, it looks it uses rte_pktmbuf_alloc(), which calls
rte_pktmbuf_reset(), fully initializing the mbuf struct. So data_off is
properly set.
As a side note, I wonder if lio_recv_buffer_alloc() replaced by
rte_pktmbuf_alloc() everywhere in the code.
Olivier
