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

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Date:   Tue, 9 Jan 2018 20:22:15 +0200
From:   Tal Gilboa <talgi@...lanox.com>
To:     Andy Gospodarek <andy@...yhouse.net>,
        Saeed Mahameed <saeedm@...lanox.com>
Cc:     netdev@...r.kernel.org, mchan@...adcom.com,
        Talat Batheesh <talatb@...lanox.com>
Subject: Re: [PATCH net-next v3 06/10] net/mlx5e: Change Mellanox references
 in DIM code

On 1/9/2018 6:06 PM, Andy Gospodarek wrote:
> On Mon, Jan 08, 2018 at 11:06:28PM -0800, Saeed Mahameed wrote:
>>
>>
>> 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.
>>
> 
> Thanks for bringing that to everyone's attention.  I agree there is
> probably not much that should be done at this point -- hopefully the
> merge should go pretty smoothly, since net_dim.h is seen as a rename
> from en_rx_am.c.

I talked with Talat, who is submitting the fix. He will apply it over 
these patches after they are accepted.

> 
> 
>>>    	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;
>>>    }