Re: [dpdk-dev] [PATCH V2 1/2] net/netvsc: allow setting rx and tx copy break

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 10/23/2020 10:54 PM, Long Li wrote:
> From: Stephen Hemminger <stephen@networkplumber.org>
> 
> The values for Rx and Tx copy break should be tunable rather
> than hard coded constants.
> 
> The rx_copybreak sets the threshold where the driver uses an
> external mbuf to avoid having to copy data. Setting 0 for copybreak
> will cause driver to always create an external mbuf. Setting
> a value greater than the MTU would prevent it from ever making
> an external mbuf and always copy. The default value is 256 (bytes).
> 
> Likewise the tx_copybreak sets the threshold where the driver
> aggregates multiple small packets into one request. If tx_copybreak
> is 0 then each packet goes as a VMBus request (no copying).
> If tx_copybreak is set larger than the MTU, then all packets smaller
> than the chunk size of the VMBus send buffer will be copied; larger
> packets always have to go as a single direct request. The default
> value is 512 (bytes).
> 
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> Signed-off-by: Long Li <longli@microsoft.com>

<...>

> @@ -181,9 +195,14 @@ static int hn_parse_args(const struct rte_eth_dev *dev)
>   		return -EINVAL;
>   	}
>   
> -	ret = rte_kvargs_process(kvlist, "latency", hn_set_latency, hv);
> -	if (ret)
> -		PMD_DRV_LOG(ERR, "Unable to process latency arg\n");
> +	for (i = 0; i < sizeof(valid_keys) / sizeof(valid_keys[0]) - 1; i++) {
> +		ret = rte_kvargs_process(kvlist, valid_keys[i],
> +					 hn_set_parameter, hv);
> +		if (ret) {
> +			PMD_DRV_LOG(ERR, "Unable to process latency arg\n");

Need to update the log, it is not only 'latency' anymore.

> +			break;
> +		}
> +	}

Since there is single callback for all args, and there is already a 'key' check 
in the callback function, why not call the 'rte_kvargs_process()' with NULL 
argument and drop the for loop:
  ret = rte_kvargs_process(kvlist, NULL, hn_set_parameter, hv);

Can you also register the devargs in .c file:
'RTE_PMD_REGISTER_PARAM_STRING'
This is to get PMD supported devargs from .so, using "./usertools/dpdk-pmdinfo.py".

Thanks,
ferruh