Commit 5758c314 authored by Maxim Mikityanskiy's avatar Maxim Mikityanskiy Committed by Jakub Kicinski
Browse files

net/mlx5e: Make the wqe_index_mask calculation more exact 



The old calculation of wqe_index_mask may give false positives, i.e.
request bulking of pairs of WQEs when not strictly needed, for example,
when the first fragment size is equal to the PAGE_SIZE, bulking is not
needed, even if the number of fragments is odd.

Make the calculation more exact to cut false positives.

Signed-off-by: default avatarMaxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: default avatarTariq Toukan <tariqt@nvidia.com>
Signed-off-by: default avatarSaeed Mahameed <saeedm@nvidia.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent a064c609

drivers/net/ethernet/mellanox/mlx5/core/en/params.c

+20 −1
Original line number Diff line number Diff line
@@ -648,7 +648,26 @@ static int mlx5e_build_rq_frags_info(struct mlx5_core_dev *mdev, 
	 * is not completed yet, WQE 2*N must not be allocated, as it's

	 * responsible for allocating a new page.

	 */

	if (frag_size_max == PAGE_SIZE) {

		/* No WQE can start in the middle of a page. */

		info->wqe_index_mask = 0;

	} else {

		/* PAGE_SIZEs starting from 8192 don't use 2K-sized fragments,

		 * because there would be more than MLX5E_MAX_RX_FRAGS of them.

		 */

		WARN_ON(PAGE_SIZE != 2 * DEFAULT_FRAG_SIZE);



		/* Odd number of fragments allows to pack the last fragment of

		 * the previous WQE and the first fragment of the next WQE into

		 * the same page.

		 * As long as DEFAULT_FRAG_SIZE is 2048, and MLX5E_MAX_RX_FRAGS

		 * is 4, the last fragment can be bigger than the rest only if

		 * it's the fourth one, so WQEs consisting of 3 fragments will

		 * always share a page.

		 * When a page is shared, WQE bulk size is 2, otherwise just 1.

		 */

		info->wqe_index_mask = info->num_frags % 2;

	}



out:

	/* Bulking optimization to skip allocation until at least 8 WQEs can be