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net/mlx5e: Make the wqe_index_mask calculation more exact

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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: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Maxim Mikityanskiy 2022-09-30 09:28:51 -07:00 committed by Jakub Kicinski
parent a064c60984
commit 5758c3145b
1 changed files with 20 additions and 1 deletions

21
drivers/net/ethernet/mellanox/mlx5/core/en/params.c

@ -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.
*/
info->wqe_index_mask = info->num_frags % 2;
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