From: Maxim Mikityanskiy <maximmi@nvidia.com>
Date: Fri, 30 Sep 2022 09:28:50 -0700
Subject: net/mlx5e: Introduce wqe_index_mask for legacy RQ
Patch-mainline: v6.1-rc1
Git-commit: a064c609849bf71adc7484b030539568cd2a5155
References: jsc#PED-1549
When fragments of different WQEs share the same page, mlx5e_post_rx_wqes
must wait until the old WQE stops using the page, only then the new WQE
can allocate the new page. Essentially, it means that if WQE index i is
still in use, the allocation must stop before `i % bulk`, where bulk is
the number of WQEs that may share the same page.
As bulk is always a power of two, `i % bulk = i & (bulk - 1)`, and the
new wqe_index_mask field will be equal to `bulk - 1`.
At the same time, wqe_bulk remains for optimization purposes and stores
`max(bulk, 8)`, which allows to skip the allocation until we have at
least 8 WQEs free.
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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
drivers/net/ethernet/mellanox/mlx5/core/en.h | 1
drivers/net/ethernet/mellanox/mlx5/core/en/params.c | 25 ++++++++++++++++----
2 files changed, 22 insertions(+), 4 deletions(-)
--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -660,6 +660,7 @@ struct mlx5e_rq_frags_info {
u8 num_frags;
u8 log_num_frags;
u8 wqe_bulk;
+ u8 wqe_index_mask;
};
struct mlx5e_dma_info {
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
@@ -586,7 +586,14 @@ static int mlx5e_build_rq_frags_info(str
info->arr[0].frag_size = byte_count;
info->arr[0].frag_stride = frag_stride;
info->num_frags = 1;
- info->wqe_bulk = PAGE_SIZE / frag_stride;
+
+ /* N WQEs share the same page, N = PAGE_SIZE / frag_stride. The
+ * first WQE in the page is responsible for allocation of this
+ * page, this WQE's index is k*N. If WQEs [k*N+1; k*N+N-1] are
+ * still not completed, the allocation must stop before k*N.
+ */
+ info->wqe_index_mask = (PAGE_SIZE / frag_stride) - 1;
+
goto out;
}
@@ -635,11 +642,21 @@ static int mlx5e_build_rq_frags_info(str
i++;
}
info->num_frags = i;
- /* number of different wqes sharing a page */
- info->wqe_bulk = 1 + (info->num_frags % 2);
+
+ /* The last fragment of WQE with index 2*N may share the page with the
+ * first fragment of WQE with index 2*N+1 in certain cases. If WQE 2*N+1
+ * 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;
out:
- info->wqe_bulk = max_t(u8, info->wqe_bulk, 8);
+ /* Bulking optimization to skip allocation until at least 8 WQEs can be
+ * allocated in a row. At the same time, never start allocation when
+ * the page is still used by older WQEs.
+ */
+ info->wqe_bulk = max_t(u8, info->wqe_index_mask + 1, 8);
+
info->log_num_frags = order_base_2(info->num_frags);
return 0;