Re: [dpdk-dev] [PATCH] net/virtio: get all pending Rx packets in altivec vectorized paths

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 9/30/19 8:42 PM, David Christensen wrote:
> The loop to read packets does not take all packets as the number of
> available packets (nb_used) is decremented in the loop.
> Take all available packets provides a performance improvement of 3%.
> 
> Fixes: fc3d66212fed ("virtio: add vector Rx")
> Cc: stable@dpdk.org
> Cc: thibaut.collet@6wind.com
> Cc: maxime.coquelin@redhat.com
> Cc: tiwei.bie@intel.com
> Cc: zhihong.wang@intel.com
> Cc: jerinj@marvell.com
> Cc: gavin.hu@arm.com
> 
Same comments as for other patch, I'll fix that whiile applying.

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks!
Maxime

> Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>
> ---
>  drivers/net/virtio/virtio_rxtx_simple_altivec.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_rxtx_simple_altivec.c b/drivers/net/virtio/virtio_rxtx_simple_altivec.c
> index f856396ab..47225f412 100644
> --- a/drivers/net/virtio/virtio_rxtx_simple_altivec.c
> +++ b/drivers/net/virtio/virtio_rxtx_simple_altivec.c
> @@ -44,7 +44,7 @@ virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
>  	struct virtnet_rx *rxvq = rx_queue;
>  	struct virtqueue *vq = rxvq->vq;
>  	struct virtio_hw *hw = vq->hw;
> -	uint16_t nb_used;
> +	uint16_t nb_used, nb_total;
>  	uint16_t desc_idx;
>  	struct vring_used_elem *rused;
>  	struct rte_mbuf **sw_ring;
> @@ -109,9 +109,10 @@ virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
>  			virtqueue_notify(vq);
>  	}
>  
> +	nb_total = nb_used;
>  	ref_rx_pkts = rx_pkts;
>  	for (nb_pkts_received = 0;
> -		nb_pkts_received < nb_used;) {
> +		nb_pkts_received < nb_total;) {
>  		vector unsigned char desc[RTE_VIRTIO_DESC_PER_LOOP / 2];
>  		vector unsigned char mbp[RTE_VIRTIO_DESC_PER_LOOP / 2];
>  		vector unsigned char pkt_mb[RTE_VIRTIO_DESC_PER_LOOP];
>