[dpdk-dev] [PATCH v2 1/3] net/af_xdp: enable zero copy by extbuf

William Tu u9012063 at gmail.com
Thu Jun 13 02:32:41 CEST 2019


On Tue, Jun 11, 2019 at 8:21 PM Ye Xiaolong <xiaolong.ye at intel.com> wrote:
>
> Hi,
>
> On 06/11, William Tu wrote:
> [snip]
> >> @@ -294,16 +326,26 @@ eth_af_xdp_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
> >>
> >>                 desc = xsk_ring_prod__tx_desc(&txq->tx, idx_tx + i);
> >>                 mbuf = bufs[i];
> >> -
> >> -               desc->addr = (uint64_t)addrs[i];
> >>                 desc->len = mbuf->pkt_len;
> >> -               pkt = xsk_umem__get_data(umem->mz->addr,
> >> -                                        desc->addr);
> >> -               rte_memcpy(pkt, rte_pktmbuf_mtod(mbuf, void *),
> >> -                          desc->len);
> >> -               tx_bytes += mbuf->pkt_len;
> >>
> >> -               rte_pktmbuf_free(mbuf);
> >> +               /*
> >> +                * We need to make sure the external mbuf address is within
> >> +                * current port's umem memzone range
> >> +                */
> >> +               if (pmd_zc && RTE_MBUF_HAS_EXTBUF(mbuf) &&
> >> +                               in_umem_range(umem, (uint64_t)mbuf->buf_addr)) {
> >> +                       desc->addr = (uint64_t)mbuf->buf_addr -
> >> +                               umem->mz->addr_64;
> >> +                       mbuf->buf_addr = xsk_umem__get_data(umem->mz->addr,
> >> +                                       (uint64_t)addrs[i]);
> >> +               } else {
> >> +                       desc->addr = (uint64_t)addrs[i];
> >> +                       pkt = xsk_umem__get_data(umem->mz->addr,
> >> +                                       desc->addr);
> >> +                       rte_memcpy(pkt, rte_pktmbuf_mtod(mbuf, void *),
> >> +                                       desc->len);
> >> +               }
> >> +               tx_bytes += mbuf->pkt_len;
> >>         }
> >>
> >>         xsk_ring_prod__submit(&txq->tx, nb_pkts);
> >> @@ -313,6 +355,9 @@ eth_af_xdp_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
> >>         txq->stats.tx_pkts += nb_pkts;
> >>         txq->stats.tx_bytes += tx_bytes;
> >>
> >> +       for (i = 0; i < nb_pkts; i++)
> >> +               rte_pktmbuf_free(bufs[i]);
> >> +
> >
> >Is it ok to free the mbuf here?
> >If the AF_XDP is running pmd_zc=true, the packet mbuf is still in the tx
> >ring and might not be sent out yet.
>
> For pmd_zc=ture case, here mbuf->buf_addr has been exchanged to available addr
> dequeued from umem->buf_ring, rte_pktmbuf_free would just call the free callback
> umem_buf_release_to_fq to enqueue the addr to the buf_ring.
>

I see, thanks for the explanation.
William

> Thanks,
> Xiaolong
>
> >
> >Regards,
> >William
> >


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