netdev - Re: [PATCH][net-next] net: drop_monitor: change the stats variable to u64 in net_dm_stats

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Date:   Thu, 22 Aug 2019 14:59:46 +0300
From:   Ido Schimmel <idosch@...sch.org>
To:     Li RongQing <lirongqing@...du.com>
Cc:     netdev@...r.kernel.org, idosch@...lanox.com
Subject: Re: [PATCH][net-next] net: drop_monitor: change the stats variable
 to u64 in net_dm_stats_put

On Thu, Aug 22, 2019 at 02:22:33PM +0800, Li RongQing wrote:
> only the element drop of struct net_dm_stats is used, so simplify it to u64

Thanks for the patch, but I don't really see the value here. The struct
allows for easy extensions in the future. What do you gain from this
change? We merely read stats and report them to user space, so I guess
it's not about performance either.

> 
> Signed-off-by: Li RongQing <lirongqing@...du.com>
> ---
>  net/core/drop_monitor.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
> index bfc024024aa3..ed10a40cf629 100644
> --- a/net/core/drop_monitor.c
> +++ b/net/core/drop_monitor.c
> @@ -1329,11 +1329,11 @@ static int net_dm_cmd_config_get(struct sk_buff *skb, struct genl_info *info)
>  	return rc;
>  }
>  
> -static void net_dm_stats_read(struct net_dm_stats *stats)
> +static void net_dm_stats_read(u64 *stats)
>  {
>  	int cpu;
>  
> -	memset(stats, 0, sizeof(*stats));
> +	*stats = 0;
>  	for_each_possible_cpu(cpu) {
>  		struct per_cpu_dm_data *data = &per_cpu(dm_cpu_data, cpu);
>  		struct net_dm_stats *cpu_stats = &data->stats;
> @@ -1345,14 +1345,14 @@ static void net_dm_stats_read(struct net_dm_stats *stats)
>  			dropped = cpu_stats->dropped;
>  		} while (u64_stats_fetch_retry_irq(&cpu_stats->syncp, start));
>  
> -		stats->dropped += dropped;
> +		*stats += dropped;
>  	}
>  }
>  
>  static int net_dm_stats_put(struct sk_buff *msg)
>  {
> -	struct net_dm_stats stats;
>  	struct nlattr *attr;
> +	u64 stats;
>  
>  	net_dm_stats_read(&stats);
>  
> @@ -1361,7 +1361,7 @@ static int net_dm_stats_put(struct sk_buff *msg)
>  		return -EMSGSIZE;
>  
>  	if (nla_put_u64_64bit(msg, NET_DM_ATTR_STATS_DROPPED,
> -			      stats.dropped, NET_DM_ATTR_PAD))
> +			      stats, NET_DM_ATTR_PAD))
>  		goto nla_put_failure;
>  
>  	nla_nest_end(msg, attr);
> -- 
> 2.16.2
>