Re: [PATCH] vhost-user: optimize stats counters performance

[Chenbo Xia <chenbox@nvidia.com>]

> On Aug 2, 2024, at 22:32, Morten Brørup <mb@smartsharesystems.com> wrote:
> 
> External email: Use caution opening links or attachments
> 
> 
> Optimized the performance of updating the statistics counters by reducing
> the number of branches.
> 
> Ordered the packet size comparisons according to the probability with
> typical internet traffic mix.
> 
> Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
> ---
> lib/vhost/virtio_net.c | 40 ++++++++++++++--------------------------
> 1 file changed, 14 insertions(+), 26 deletions(-)
> 
> diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
> index 370402d849..25a495df56 100644
> --- a/lib/vhost/virtio_net.c
> +++ b/lib/vhost/virtio_net.c
> @@ -53,7 +53,7 @@ is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t nr_vring)
> }
> 
> static inline void
> -vhost_queue_stats_update(struct virtio_net *dev, struct vhost_virtqueue *vq,
> +vhost_queue_stats_update(const struct virtio_net *dev, struct vhost_virtqueue *vq,
>                struct rte_mbuf **pkts, uint16_t count)
>        __rte_shared_locks_required(&vq->access_lock)
> {
> @@ -64,37 +64,25 @@ vhost_queue_stats_update(struct virtio_net *dev, struct vhost_virtqueue *vq,
>                return;
> 
>        for (i = 0; i < count; i++) {
> -               struct rte_ether_addr *ea;
> -               struct rte_mbuf *pkt = pkts[i];
> +               const struct rte_ether_addr *ea;
> +               const struct rte_mbuf *pkt = pkts[i];
>                uint32_t pkt_len = rte_pktmbuf_pkt_len(pkt);
> 
>                stats->packets++;
>                stats->bytes += pkt_len;
> 
> -               if (pkt_len == 64) {
> -                       stats->size_bins[1]++;
> -               } else if (pkt_len > 64 && pkt_len < 1024) {
> -                       uint32_t bin;
> -
> -                       /* count zeros, and offset into correct bin */
> -                       bin = (sizeof(pkt_len) * 8) - rte_clz32(pkt_len) - 5;
> -                       stats->size_bins[bin]++;
> -               } else {
> -                       if (pkt_len < 64)
> -                               stats->size_bins[0]++;
> -                       else if (pkt_len < 1519)
> -                               stats->size_bins[6]++;
> -                       else
> -                               stats->size_bins[7]++;
> -               }
> +               if (pkt_len >= 1024)
> +                       stats->size_bins[6 + (pkt_len > 1518)]++;
> +               else if (pkt_len <= 64)
> +                       stats->size_bins[pkt_len >> 6]++;
> +               else
> +                       stats->size_bins[32UL - rte_clz32(pkt_len) - 5]++;
> 
> -               ea = rte_pktmbuf_mtod(pkt, struct rte_ether_addr *);
> -               if (rte_is_multicast_ether_addr(ea)) {
> -                       if (rte_is_broadcast_ether_addr(ea))
> -                               stats->broadcast++;
> -                       else
> -                               stats->multicast++;
> -               }
> +               ea = rte_pktmbuf_mtod(pkt, const struct rte_ether_addr *);
> +               RTE_BUILD_BUG_ON(offsetof(struct virtqueue_stats, broadcast) !=
> +                               offsetof(struct virtqueue_stats, multicast) + sizeof(uint64_t));
> +               if (unlikely(rte_is_multicast_ether_addr(ea)))
> +                       (&stats->multicast)[rte_is_broadcast_ether_addr(ea)]++;
>        }
> }
> 
> --
> 2.43.0
> 

Reviewed-by: Chenbo Xia <chenbox@nvidia.com>