Re: [dpdk-dev] [PATCH 2/4] examples/l3fwd: eliminate unnecessary calculations

[Jerin Jacob <jerinjacobk@gmail.com>]

On Thu, Mar 18, 2021 at 3:56 PM Ruifeng Wang <ruifeng.wang@arm.com> wrote:
>
> Both L2 and L3 headers will be used in forward processing. And these
> two headers are in the same cache line. It has the same effect for
> prefetching with L2 header address and prefetching with L3 header
> address.
>
> Changed to use L2 header address for prefetching. The change showed
> no measurable performance improvement, but it definitely removed

Same here.

> unnecessary instructions for address calculation.


>
> Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>

Acked-by: Jerin Jacob <jerinj@marvell.com>


> ---
>  examples/l3fwd/l3fwd_lpm_neon.h | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/examples/l3fwd/l3fwd_lpm_neon.h b/examples/l3fwd/l3fwd_lpm_neon.h
> index ae8840694..1650ae444 100644
> --- a/examples/l3fwd/l3fwd_lpm_neon.h
> +++ b/examples/l3fwd/l3fwd_lpm_neon.h
> @@ -98,14 +98,14 @@ l3fwd_lpm_send_packets(int nb_rx, struct rte_mbuf **pkts_burst,
>         if (k) {
>                 for (i = 0; i < FWDSTEP; i++) {
>                         rte_prefetch0_write(rte_pktmbuf_mtod(pkts_burst[i],
> -                                               struct rte_ether_hdr *) + 1);
> +                                                       void *));
>                 }
>
>                 for (j = 0; j != k - FWDSTEP; j += FWDSTEP) {
>                         for (i = 0; i < FWDSTEP; i++) {
>                                 rte_prefetch0_write(rte_pktmbuf_mtod(
>                                                 pkts_burst[j + i + FWDSTEP],
> -                                               struct rte_ether_hdr *) + 1);
> +                                               void *));
>                         }
>
>                         processx4_step1(&pkts_burst[j], &dip, &ipv4_flag);
> @@ -125,17 +125,17 @@ l3fwd_lpm_send_packets(int nb_rx, struct rte_mbuf **pkts_burst,
>                 switch (m) {
>                 case 3:
>                         rte_prefetch0_write(rte_pktmbuf_mtod(pkts_burst[j],
> -                                               struct rte_ether_hdr *) + 1);
> +                                                       void *));
>                         j++;
>                         /* fallthrough */
>                 case 2:
>                         rte_prefetch0_write(rte_pktmbuf_mtod(pkts_burst[j],
> -                                               struct rte_ether_hdr *) + 1);
> +                                                       void *));
>                         j++;
>                         /* fallthrough */
>                 case 1:
>                         rte_prefetch0_write(rte_pktmbuf_mtod(pkts_burst[j],
> -                                               struct rte_ether_hdr *) + 1);
> +                                                       void *));
>                         j++;
>                 }
>
> --
> 2.25.1
>