Subject: Re: [RFC net-next] net: mvneta: align xdp stats naming scheme to mlx5 driver

From: Jesper Dangaard Brouer <[email-masked]>
Date: Tue, 18 Feb 2020 18:02:10 +0100

On Tue, 18 Feb 2020 01:14:29 +0100
Lorenzo Bianconi <[email-masked]> wrote:

> Introduce "rx" prefix in the name scheme for xdp counters
> on rx path.
> Differentiate between XDP_TX and ndo_xdp_xmit counters
> 
> Signed-off-by: Lorenzo Bianconi <[email-masked]>
> ---
>  drivers/net/ethernet/marvell/mvneta.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index b7045b6a15c2..6223700dc3df 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -344,6 +344,7 @@ enum {
>  	ETHTOOL_XDP_REDIRECT,
>  	ETHTOOL_XDP_PASS,
>  	ETHTOOL_XDP_DROP,
> +	ETHTOOL_XDP_XMIT,
>  	ETHTOOL_XDP_TX,
>  	ETHTOOL_MAX_STATS,
>  };
> @@ -399,10 +400,11 @@ static const struct mvneta_statistic mvneta_statistics[] = {
>  	{ ETHTOOL_STAT_EEE_WAKEUP, T_SW, "eee_wakeup_errors", },
>  	{ ETHTOOL_STAT_SKB_ALLOC_ERR, T_SW, "skb_alloc_errors", },
>  	{ ETHTOOL_STAT_REFILL_ERR, T_SW, "refill_errors", },
> -	{ ETHTOOL_XDP_REDIRECT, T_SW, "xdp_redirect", },
> -	{ ETHTOOL_XDP_PASS, T_SW, "xdp_pass", },
> -	{ ETHTOOL_XDP_DROP, T_SW, "xdp_drop", },
> -	{ ETHTOOL_XDP_TX, T_SW, "xdp_tx", },
> +	{ ETHTOOL_XDP_REDIRECT, T_SW, "rx_xdp_redirect", },
> +	{ ETHTOOL_XDP_PASS, T_SW, "rx_xdp_pass", },
> +	{ ETHTOOL_XDP_DROP, T_SW, "rx_xdp_drop", },
> +	{ ETHTOOL_XDP_TX, T_SW, "rx_xdp_tx_xmit", },

Hmmm... "rx_xdp_tx_xmit", I expected this to be named "rx_xdp_tx" to
count the XDP_TX actions, but I guess this means something else.

> +	{ ETHTOOL_XDP_XMIT, T_SW, "tx_xdp_xmit", },

Okay, maybe.  I guess, this will still be valid for when we add an XDP
egress/TX-hook point.

>  };
>  
>  struct mvneta_stats {
> @@ -414,6 +416,7 @@ struct mvneta_stats {
>  	u64	xdp_redirect;
>  	u64	xdp_pass;
>  	u64	xdp_drop;
> +	u64	xdp_xmit;
>  	u64	xdp_tx;
>  };
>  
> @@ -2050,7 +2053,10 @@ mvneta_xdp_submit_frame(struct mvneta_port *pp, struct mvneta_tx_queue *txq,
>  	u64_stats_update_begin(&stats->syncp);
>  	stats->es.ps.tx_bytes += xdpf->len;
>  	stats->es.ps.tx_packets++;
> -	stats->es.ps.xdp_tx++;
> +	if (buf->type == MVNETA_TYPE_XDP_NDO)
> +		stats->es.ps.xdp_xmit++;
> +	else
> +		stats->es.ps.xdp_tx++;

I don't like that you add a branch (if-statement) in this fast-path code.

Do we really need to account in the xmit frame function, if this was a
XDP_REDIRECT or XDP_TX that started the xmit?  I mean we already have
action counters for XDP_REDIRECT and XDP_TX (but I guess you skipped
the XDP_TX action counter). 

>  	u64_stats_update_end(&stats->syncp);
>  
>  	mvneta_txq_inc_put(txq);
> @@ -4484,6 +4490,7 @@ mvneta_ethtool_update_pcpu_stats(struct mvneta_port *pp,
>  		u64 xdp_redirect;
>  		u64 xdp_pass;
>  		u64 xdp_drop;
> +		u64 xdp_xmit;
>  		u64 xdp_tx;
>  
>  		stats = per_cpu_ptr(pp->stats, cpu);
> @@ -4494,6 +4501,7 @@ mvneta_ethtool_update_pcpu_stats(struct mvneta_port *pp,
>  			xdp_redirect = stats->es.ps.xdp_redirect;
>  			xdp_pass = stats->es.ps.xdp_pass;
>  			xdp_drop = stats->es.ps.xdp_drop;
> +			xdp_xmit = stats->es.ps.xdp_xmit;
>  			xdp_tx = stats->es.ps.xdp_tx;
>  		} while (u64_stats_fetch_retry_irq(&stats->syncp, start));
>  
> @@ -4502,6 +4510,7 @@ mvneta_ethtool_update_pcpu_stats(struct mvneta_port *pp,
>  		es->ps.xdp_redirect += xdp_redirect;
>  		es->ps.xdp_pass += xdp_pass;
>  		es->ps.xdp_drop += xdp_drop;
> +		es->ps.xdp_xmit += xdp_xmit;
>  		es->ps.xdp_tx += xdp_tx;
>  	}
>  }
> @@ -4555,6 +4564,9 @@ static void mvneta_ethtool_update_stats(struct mvneta_port *pp)
>  			case ETHTOOL_XDP_TX:
>  				pp->ethtool_stats[i] = stats.ps.xdp_tx;
>  				break;
> +			case ETHTOOL_XDP_XMIT:
> +				pp->ethtool_stats[i] = stats.ps.xdp_xmit;
> +				break;
>  			}
>  			break;
>  		}

It doesn't look like you have an action counter for XDP_TX, but we have
one for XDP_REDIRECT?

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer