-----Original Message-----
> Date: Wed, 11 Jul 2018 13:54:36 +0530
> From: Kiran Kumar <kkokkilaga...@caviumnetworks.com>
> To: jerin.ja...@caviumnetworks.com, maciej.cze...@caviumnetworks.com,
> ferruh.yi...@intel.com
> Cc: dev@dpdk.org, Kiran Kumar <kkokkilaga...@caviumnetworks.com>,
> sta...@dpdk.org
> Subject: [dpdk-dev] [PATCH v2] net/thunderx: avoid sq door bell writes on
> zero packets
> X-Mailer: git-send-email 2.7.4
>
> Avoid sq door bell write on zero packet case to reduce additional
> traffic on register bus.
>
> Fixes: 1c421f18e0 ("net/thunderx: add single and multi-segment Tx")
> Cc: sta...@dpdk.org
>
> Signed-off-by: Kiran Kumar <kkokkilaga...@caviumnetworks.com>
Acked-by: Jerin Jacob <jerin.ja...@caviumnetworks.com>
> ---
> v2 Changes:
> - changed summery and description.
> - added same optimization to nicvf_xmit_pkts_multiseg
>
> drivers/net/thunderx/nicvf_rxtx.c | 24 ++++++++++++++----------
> 1 file changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/net/thunderx/nicvf_rxtx.c
> b/drivers/net/thunderx/nicvf_rxtx.c
> index 72305d9..6e075e2 100644
> --- a/drivers/net/thunderx/nicvf_rxtx.c
> +++ b/drivers/net/thunderx/nicvf_rxtx.c
> @@ -162,12 +162,14 @@ nicvf_xmit_pkts(void *tx_queue, struct rte_mbuf
> **tx_pkts, uint16_t nb_pkts)
> free_desc -= TX_DESC_PER_PKT;
> }
>
> - sq->tail = tail;
> - sq->xmit_bufs += i;
> - rte_wmb();
> + if (likely(i)) {
> + sq->tail = tail;
> + sq->xmit_bufs += i;
> + rte_wmb();
>
> - /* Inform HW to xmit the packets */
> - nicvf_addr_write(sq->sq_door, i * TX_DESC_PER_PKT);
> + /* Inform HW to xmit the packets */
> + nicvf_addr_write(sq->sq_door, i * TX_DESC_PER_PKT);
> + }
> return i;
> }
>
> @@ -218,12 +220,14 @@ nicvf_xmit_pkts_multiseg(void *tx_queue, struct
> rte_mbuf **tx_pkts,
> }
> }
>
> - sq->tail = tail;
> - sq->xmit_bufs += used_bufs;
> - rte_wmb();
> + if (likely(used_desc)) {
> + sq->tail = tail;
> + sq->xmit_bufs += used_bufs;
> + rte_wmb();
>
> - /* Inform HW to xmit the packets */
> - nicvf_addr_write(sq->sq_door, used_desc);
> + /* Inform HW to xmit the packets */
> + nicvf_addr_write(sq->sq_door, used_desc);
> + }
> return i;
> }
>
> --
> 2.7.4
>
