Re: [dpdk-dev] [PATCH 1/2] net/tap: remove redundant syscall on Tx

["Wiles, Keith" <keith.wiles@intel.com>]

> On Mar 14, 2017, at 8:51 PM, Adrien Mazarguil <adrien.mazarguil@6wind.com> wrote:
> 
> Polling the Tx queue file descriptor before writing to it is not mandatory
> since it is configured as non-blocking.
> 
> Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
> Acked-by: Pascal Mazon <pascal.mazon@6wind.com>

Acked-by: Keith Wiles <keith.wiles@intel.com>

> ---
> drivers/net/tap/rte_eth_tap.c | 26 ++++++++------------------
> 1 file changed, 8 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
> index efc4426..c757a7c 100644
> --- a/drivers/net/tap/rte_eth_tap.c
> +++ b/drivers/net/tap/rte_eth_tap.c
> @@ -43,7 +43,6 @@
> #include <sys/ioctl.h>
> #include <sys/mman.h>
> #include <unistd.h>
> -#include <poll.h>
> #include <arpa/inet.h>
> #include <linux/if.h>
> #include <linux/if_tun.h>
> @@ -242,7 +241,6 @@ pmd_tx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
> {
> 	struct rte_mbuf *mbuf;
> 	struct tx_queue *txq = queue;
> -	struct pollfd pfd;
> 	uint16_t num_tx = 0;
> 	unsigned long num_tx_bytes = 0;
> 	int i, n;
> @@ -250,26 +248,18 @@ pmd_tx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
> 	if (unlikely(nb_pkts == 0))
> 		return 0;
> 
> -	pfd.events = POLLOUT;
> -	pfd.fd = txq->fd;
> 	for (i = 0; i < nb_pkts; i++) {
> -		n = poll(&pfd, 1, 0);
> -
> +		/* copy the tx frame data */
> +		mbuf = bufs[num_tx];
> +		n = write(txq->fd,
> +			  rte_pktmbuf_mtod(mbuf, void *),
> +			  rte_pktmbuf_pkt_len(mbuf));
> 		if (n <= 0)
> 			break;
> 
> -		if (pfd.revents & POLLOUT) {
> -			/* copy the tx frame data */
> -			mbuf = bufs[num_tx];
> -			n = write(pfd.fd, rte_pktmbuf_mtod(mbuf, void*),
> -				  rte_pktmbuf_pkt_len(mbuf));
> -			if (n <= 0)
> -				break;
> -
> -			num_tx++;
> -			num_tx_bytes += mbuf->pkt_len;
> -			rte_pktmbuf_free(mbuf);
> -		}
> +		num_tx++;
> +		num_tx_bytes += mbuf->pkt_len;
> +		rte_pktmbuf_free(mbuf);
> 	}
> 
> 	txq->stats.opackets += num_tx;
> -- 
> 2.1.4
> 

Regards,
Keith