netdev - Re: [PATCH net-next v3 06/10] net/mlx5e: Change Mellanox references in DIM code

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Date:   Mon, 8 Jan 2018 23:06:28 -0800
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     Andy Gospodarek <andy@...yhouse.net>, netdev@...r.kernel.org
Cc:     mchan@...adcom.com, talgi@...lanox.com, ogerlitz@...lanox.com,
        Andy Gospodarek <gospo@...adcom.com>
Subject: Re: [PATCH net-next v3 06/10] net/mlx5e: Change Mellanox references
 in DIM code



On 01/08/2018 10:13 PM, Andy Gospodarek wrote:
> From: Andy Gospodarek <gospo@...adcom.com>
> 
> Change all appropriate mlx5_am* and MLX5_AM* references to net_dim and
> NET_DIM, respectively, in code that handles dynamic interrupt
> moderation.  Also change all references from 'am' to 'dim' when used as
> local variables and add generic profile references.
> 
> Signed-off-by: Andy Gospodarek <gospo@...adcom.com>
> Acked-by: Tal Gilboa <talgi@...lanox.com>
> Acked-by: Saeed Mahameed <saeedm@...lanox.com>
> ---
>   drivers/net/ethernet/mellanox/mlx5/core/en.h       |   9 +-
>   drivers/net/ethernet/mellanox/mlx5/core/en_dim.c   |  14 +-
>   .../net/ethernet/mellanox/mlx5/core/en_ethtool.c   |   6 +-
>   drivers/net/ethernet/mellanox/mlx5/core/en_main.c  |  40 ++-
>   drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c  |   8 +-
>   drivers/net/ethernet/mellanox/mlx5/core/net_dim.c  | 286 ++++++++++-----------
>   drivers/net/ethernet/mellanox/mlx5/core/net_dim.h  |  63 ++---
>   7 files changed, 225 insertions(+), 201 deletions(-)
> 

[...]

>   
>   #define IS_SIGNIFICANT_DIFF(val, ref) \
>   	(((100 * abs((val) - (ref))) / (ref)) > 10) /* more than 10% difference */
>   
> -static int mlx5e_am_stats_compare(struct mlx5e_rx_am_stats *curr,
> -				  struct mlx5e_rx_am_stats *prev)
> +static int net_dim_stats_compare(struct net_dim_stats *curr,
> +				 struct net_dim_stats *prev)
>   {
>   	if (!prev->bpms)
> -		return curr->bpms ? MLX5E_AM_STATS_BETTER :
> -				    MLX5E_AM_STATS_SAME;
> +		return curr->bpms ? NET_DIM_STATS_BETTER :
> +				    NET_DIM_STATS_SAME;
>   
>   	if (IS_SIGNIFICANT_DIFF(curr->bpms, prev->bpms))
> -		return (curr->bpms > prev->bpms) ? MLX5E_AM_STATS_BETTER :
> -						   MLX5E_AM_STATS_WORSE;
> +		return (curr->bpms > prev->bpms) ? NET_DIM_STATS_BETTER :
> +						   NET_DIM_STATS_WORSE;
>   

Hey Andy,

I am currently reviewing a patch internally that fixes a bug in this 
area, prev->ppms can be 0 and could cause IS_SIGNIFICANT_DIFF ouch !
same goes for prev->eppm, for some reason we had a broken assumption 
that if ppms is 0 for some reason then the bpms is 0 and the above 
condition will cover us.

Anyway the patch will go to net, which means when this series gets 
accepted then net-next will fail to merge with net and we need to 
manually push the fix to the new DIM library.

But for now I don't think anything is required for this series other 
than bringing this division by 0 issue and the future merge conflict to 
your attention.

>   	if (IS_SIGNIFICANT_DIFF(curr->ppms, prev->ppms))
> -		return (curr->ppms > prev->ppms) ? MLX5E_AM_STATS_BETTER :
> -						   MLX5E_AM_STATS_WORSE;
> +		return (curr->ppms > prev->ppms) ? NET_DIM_STATS_BETTER :
> +						   NET_DIM_STATS_WORSE;
>   
>   	if (IS_SIGNIFICANT_DIFF(curr->epms, prev->epms))
> -		return (curr->epms < prev->epms) ? MLX5E_AM_STATS_BETTER :
> -						   MLX5E_AM_STATS_WORSE;
> +		return (curr->epms < prev->epms) ? NET_DIM_STATS_BETTER :
> +						   NET_DIM_STATS_WORSE;
>   
> -	return MLX5E_AM_STATS_SAME;
> +	return NET_DIM_STATS_SAME;
>   }
>