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

On Mon, Jan 08, 2018 at 11:06:28PM -0800, Saeed Mahameed wrote:

On 01/08/2018 10:13 PM, Andy Gospodarek wrote:

quoted

From: Andy Gospodarek <redacted>

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 <redacted>
Acked-by: Tal Gilboa <redacted>
Acked-by: Saeed Mahameed <redacted>
---
  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(-)

[...]

quoted

  #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.

quoted

  	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;
  }