Re: [dpdk-dev] [PATCH v3 3/7] ethdev: expose extended error stats

[Olivier MATZ <olivier.matz@6wind.com>]

Hi Maryam,

On 06/26/2015 02:59 PM, Maryam Tahhan wrote:
> Extend rte_eth_xstats_get to retrieve additional stats from the device
> driver as well the ethdev generic stats.
> 
> Signed-off-by: Maryam Tahhan <maryam.tahhan@intel.com>
> ---
>  drivers/net/ixgbe/ixgbe_ethdev.c |  2 +-
>  lib/librte_ether/rte_ethdev.c    | 20 ++++++++++++++------
>  2 files changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/ixgbe/ixgbe_ethdev.c b/drivers/net/ixgbe/ixgbe_ethdev.c
> index 0f62bcb..099e464 100644
> --- a/drivers/net/ixgbe/ixgbe_ethdev.c
> +++ b/drivers/net/ixgbe/ixgbe_ethdev.c
> @@ -2035,7 +2035,7 @@ ixgbe_dev_xstats_get(struct rte_eth_dev *dev, struct rte_eth_xstats *xstats,
>  	total_qprdc = 0;
>  	rxnfgpc = 0;
>  	txdgpc = 0;
> -	count = 0;
> +	count = n;
>  
>  	ixgbe_read_stats_registers(hw, hw_stats, &total_missed_rx, &total_qbrc,
>  							   &total_qprc, &rxnfgpc, &txdgpc, &total_qprdc);
> diff --git a/lib/librte_ether/rte_ethdev.c b/lib/librte_ether/rte_ethdev.c
> index 02cd07f..6451621 100644
> --- a/lib/librte_ether/rte_ethdev.c
> +++ b/lib/librte_ether/rte_ethdev.c
> @@ -1741,7 +1741,7 @@ rte_eth_xstats_get(uint8_t port_id, struct rte_eth_xstats *xstats,
>  {
>  	struct rte_eth_stats eth_stats;
>  	struct rte_eth_dev *dev;
> -	unsigned count, i, q;
> +	unsigned count = 0, xcount = 0, i, q;
>  	uint64_t val, *stats_ptr;
>  
>  	if (!rte_eth_dev_is_valid_port(port_id)) {
> @@ -1751,14 +1751,18 @@ rte_eth_xstats_get(uint8_t port_id, struct rte_eth_xstats *xstats,
>  
>  	dev = &rte_eth_devices[port_id];
>  
> -	/* implemented by the driver */
> -	if (dev->dev_ops->xstats_get != NULL)
> -		return (*dev->dev_ops->xstats_get)(dev, xstats, n);
> -
> -	/* else, return generic statistics */
> +	/* Return generic statistics */
>  	count = RTE_NB_STATS;
>  	count += dev->data->nb_rx_queues * RTE_NB_RXQ_STATS;
>  	count += dev->data->nb_tx_queues * RTE_NB_TXQ_STATS;
> +
> +	/* implemented by the driver */
> +	if (dev->dev_ops->xstats_get != NULL) {
> +		/* Retrieve the additional count size */
> +		xcount = (*dev->dev_ops->xstats_get)(dev, xstats, 0);
> +		count += xcount;
> +	}
> +
>  	if (n < count)
>  		return count;
>  
> @@ -1805,6 +1809,10 @@ rte_eth_xstats_get(uint8_t port_id, struct rte_eth_xstats *xstats,
>  		}
>  	}
>  
> +	/* Display stats after the generic stats*/
> +	if (dev->dev_ops->xstats_get != NULL)
> +		(*dev->dev_ops->xstats_get)(dev, xstats, count);
> +
>  	return count;
>  }
>  

I think we can avoid to have 2 calls to dev->dev_ops->xstats_get.

The first call can be removed.
The second call could be as below:

if (dev->dev_ops->xstats_get != NULL) {
	ret = (*dev->dev_ops->xstats_get)(dev, &xstats[count],
		n - count);
	if (ret < 0)
		return ret;
	return ret + count;
}

- if the driver returns -1, the error code is propagated
- if the driver returns a positive value, it is added to "count",
  which is the number of generic stats. It can be higher than "n"
  if the xstats table is too small

Regards,
Olivier