Re: [dpdk-dev] [PATCH v2] net/vhost: merge vhost stats loop in vhost Tx/Rx

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

Hi,

On 9/28/21 03:43, Gaoxiang Liu wrote:
> To improve performance in vhost Tx/Rx, merge vhost stats loop.
> eth_vhost_tx has 2 loop of send num iteraion.
> It can be merge into one.
> eth_vhost_rx has the same issue as Tx.
> 
> Fixes: 4d6cf2ac93dc ("net/vhost: add extended statistics")

Please remove the Fixes tag, this is an optimization, not a fix.

> 
> Signed-off-by: Gaoxiang Liu <gaoxiangliu0@163.com>
> ---
> 
> v2:
>   * Fix coding style issues.
> ---
>   drivers/net/vhost/rte_eth_vhost.c | 62 ++++++++++++++-----------------
>   1 file changed, 28 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/net/vhost/rte_eth_vhost.c b/drivers/net/vhost/rte_eth_vhost.c
> index a202931e9a..a4129980f2 100644
> --- a/drivers/net/vhost/rte_eth_vhost.c
> +++ b/drivers/net/vhost/rte_eth_vhost.c
> @@ -336,38 +336,29 @@ vhost_count_xcast_packets(struct vhost_queue *vq,
>   }
>   
>   static void
> -vhost_update_packet_xstats(struct vhost_queue *vq, struct rte_mbuf **bufs,
> -			   uint16_t count, uint64_t nb_bytes,
> -			   uint64_t nb_missed)
> +vhost_update_single_packet_xstats(struct vhost_queue *vq, struct rte_mbuf *buf)

I tried to build without and with your patch, and I think that what can
explain most of the performance difference is that without your patch
the function is not inlined, whereas it is implicitely inlined with your
patch applied.

I agree with your patch, but I think we might add __rte_always_inline to
this function to make it explicit. What do you think?

Other than that:

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

Thanks,
Maxime


>   {
>   	uint32_t pkt_len = 0;
> -	uint64_t i = 0;
>   	uint64_t index;
>   	struct vhost_stats *pstats = &vq->stats;
>   
> -	pstats->xstats[VHOST_BYTE] += nb_bytes;
> -	pstats->xstats[VHOST_MISSED_PKT] += nb_missed;
> -	pstats->xstats[VHOST_UNICAST_PKT] += nb_missed;
> -
> -	for (i = 0; i < count ; i++) {
> -		pstats->xstats[VHOST_PKT]++;
> -		pkt_len = bufs[i]->pkt_len;
> -		if (pkt_len == 64) {
> -			pstats->xstats[VHOST_64_PKT]++;
> -		} else if (pkt_len > 64 && pkt_len < 1024) {
> -			index = (sizeof(pkt_len) * 8)
> -				- __builtin_clz(pkt_len) - 5;
> -			pstats->xstats[index]++;
> -		} else {
> -			if (pkt_len < 64)
> -				pstats->xstats[VHOST_UNDERSIZE_PKT]++;
> -			else if (pkt_len <= 1522)
> -				pstats->xstats[VHOST_1024_TO_1522_PKT]++;
> -			else if (pkt_len > 1522)
> -				pstats->xstats[VHOST_1523_TO_MAX_PKT]++;
> -		}
> -		vhost_count_xcast_packets(vq, bufs[i]);
> +	pstats->xstats[VHOST_PKT]++;
> +	pkt_len = buf->pkt_len;
> +	if (pkt_len == 64) {
> +		pstats->xstats[VHOST_64_PKT]++;
> +	} else if (pkt_len > 64 && pkt_len < 1024) {
> +		index = (sizeof(pkt_len) * 8)
> +			- __builtin_clz(pkt_len) - 5;
> +		pstats->xstats[index]++;
> +	} else {
> +		if (pkt_len < 64)
> +			pstats->xstats[VHOST_UNDERSIZE_PKT]++;
> +		else if (pkt_len <= 1522)
> +			pstats->xstats[VHOST_1024_TO_1522_PKT]++;
> +		else if (pkt_len > 1522)
> +			pstats->xstats[VHOST_1523_TO_MAX_PKT]++;
>   	}
> +	vhost_count_xcast_packets(vq, buf);
>   }
>   
>   static uint16_t
> @@ -376,7 +367,6 @@ eth_vhost_rx(void *q, struct rte_mbuf **bufs, uint16_t nb_bufs)
>   	struct vhost_queue *r = q;
>   	uint16_t i, nb_rx = 0;
>   	uint16_t nb_receive = nb_bufs;
> -	uint64_t nb_bytes = 0;
>   
>   	if (unlikely(rte_atomic32_read(&r->allow_queuing) == 0))
>   		return 0;
> @@ -411,11 +401,11 @@ eth_vhost_rx(void *q, struct rte_mbuf **bufs, uint16_t nb_bufs)
>   		if (r->internal->vlan_strip)
>   			rte_vlan_strip(bufs[i]);
>   
> -		nb_bytes += bufs[i]->pkt_len;
> -	}
> +		r->stats.bytes += bufs[i]->pkt_len;
> +		r->stats.xstats[VHOST_BYTE] += bufs[i]->pkt_len;
>   
> -	r->stats.bytes += nb_bytes;
> -	vhost_update_packet_xstats(r, bufs, nb_rx, nb_bytes, 0);
> +		vhost_update_single_packet_xstats(r, bufs[i]);
> +	}
>   
>   out:
>   	rte_atomic32_set(&r->while_queuing, 0);
> @@ -471,16 +461,20 @@ eth_vhost_tx(void *q, struct rte_mbuf **bufs, uint16_t nb_bufs)
>   			break;
>   	}
>   
> -	for (i = 0; likely(i < nb_tx); i++)
> +	for (i = 0; likely(i < nb_tx); i++) {
>   		nb_bytes += bufs[i]->pkt_len;
> +		vhost_update_single_packet_xstats(r, bufs[i]);
> +	}
>   
>   	nb_missed = nb_bufs - nb_tx;
>   
>   	r->stats.pkts += nb_tx;
>   	r->stats.bytes += nb_bytes;
> -	r->stats.missed_pkts += nb_bufs - nb_tx;
> +	r->stats.missed_pkts += nb_missed;
>   
> -	vhost_update_packet_xstats(r, bufs, nb_tx, nb_bytes, nb_missed);
> +	r->stats.xstats[VHOST_BYTE] += nb_bytes;
> +	r->stats.xstats[VHOST_MISSED_PKT] += nb_missed;
> +	r->stats.xstats[VHOST_UNICAST_PKT] += nb_missed;
>   
>   	/* According to RFC2863, ifHCOutUcastPkts, ifHCOutMulticastPkts and
>   	 * ifHCOutBroadcastPkts counters are increased when packets are not
>